Larry vs Harry Bullitt – Put On The Brakes!

I mean that literally. We’re going to go over choosing and putting on the brakes in this frame-up bicycle build discussion.

The Bullitt Build
1. Battery and Battery Box
2. Cargo Box
3. Brakes (you are here)
4. Front Motor & Wheel
5. Rear Motor & Drivetrain
6. Bits & Pieces

Now there is a separate series on Bullitt II: hidden battery box. Onboard charger. Etc.

For me, the choice of brakes are easy: I use Magura MT5e brakes on all my bikes and the Lizzard King was no exception. Poke around and you will see the MT5e is arguably the best ebike brakeset on the planet – even over and above the new MT7e (which provides identical calipers and brake levers… the stickers are different, plastic caliper covers are yellow not silver and the only functional difference is slightly better pads you can buy yourself – after you wear out the perfectly good ones that come with the MT5e’s).

I also use a less expensive but better rotor, as seen in the above headliner photo. But I’m getting ahead of myself here. By and large, this is an entirely mundane brake installation, with the exception of an extra-long front brake hose, plus some tweaks on pad choice. Lets begin with the…

Hoses

For the rear axle, its a totally generic job. The brake hose simply runs along the guides of the top tube and down the non drive-side chainstay to the caliper. Zip tie the hose to the existing mounts on the frame and job done.

Well, not exactly. You will want to cut down the 2200mm hose that comes with the brakes, and unless you are very careful (it can be done and Magura shows you how in their Youtube videos) you will have to bleed the hoses after cutting them, then reattaching the sized hoses to the lever.

If you are using the standard Bullitt frame kit, you have a Satori Easy Up, which allows you to raise the handlebars temporarily so you don’t bonk a passenger on the head with your handlebars as you ride. When you size your brake hoses, do so with the Easy Up fully extended.


Its the front mount that needs special attention. On a normal Bullitt, running the hose the way Larry Vs. Harry intended, they specify a 2350mm hose length. I heard 2750mm in a discussion with Splendid Cycles, and I think they are more right than wrong by going long. Either number is well beyond the 2200mm provided with the Maguras in their caliper/hose/lever kit.

Note:
My needs for running brake hose from the front wheel are different than most because I had a battery box where a normal Bullitt would run its brake hose.

So this is going to be one long hose; longer than is needed on a tandem, so you are going to have limited options. If you dig around, you will find a few sources for extra long hoses. You may hear the recommendation to use one of a couple of extension solutions that use a butt-end connector to bridge two hoses. These will work, but I won’t discuss them because thankfully, I found other options:

Jagwire Pro Hydraulic MTB Hose Kit

This can be purchased on Amazon and comes with a single 3000mm hose. You are supposed to cut that 3000mm somewhere in the middle so it is enough brake hose for both your front and rear brakes. On a normal bike thats plenty of hose for front and rear. For a Bullitt its enough for the front only. You will also have to buy the hose end kit for your brand of brakes. Naturally, those are sold separately. I bought this one for Magura brakes. It should be noted the only reason I bought this is because – most likely thanks to COVID shipping delays and general global chaos across the planet – the next option listed was taking months to deliver. In the end I didn’t use this Jagwire kit because the following finally arrived:

Custom Hoses (from Austria)

Via Ebay from seller ‘judma‘. There is no telling how long this link will last… The green ones I bought are already gone and only orange and white remain for sale (for now? Maybe they’ll come back?). I didn’t want colored hoses so much as I wanted 1-piece hoses, and this seller had a particularly useful option: I could specify the custom length of each hose. So I specified 3000mm (I actually got about 2950) for the front and a lesser, specific size for the rear. Since these hosesalready had the ends properly machine-pressed on, I opted to use them. However the neon green was a little too bright. I toned it down by covering it with dull green heatshrink tubing, from the caliper to where it entered the cargo area (more on that later) and with black heatshrink after its exit into the sunshine near the handlebars. These hoses turned out to be of top quality.

A blindingly Neon green brake hose gets toned down with a dull green heatshrink as a permanent cover.

An Alternate Path

In post-publication discussions about this article on the Bullitt – the Dark Side group on Facebook (thanks to Arild V. for bringing this up), it was pointed out Magura sells extension hoses alone in 2500mm lengths. Thats another avenue to the same goal, then: Buy an MT5e kit, still (buying a lever and a caliper outside of the kit is much more money than just buying the kit and stashing the hose that comes with it for some future project). Then buy a 2500mm 90-degree hose. Substitute this hose for the one in the kit. You will have to have a complete bleed kit and all tools necessary to redo Magura brake hoses (you should have this anyway).

If you live in the USA like I do, this is nowhere near as attractive of an option as it is in the EU. Magura brakes and parts are double or triple the cost here. This 2500mm Magura hose in the USA runs about US$65-US$70.

After this discussion I decided to go measure my brake hose on the bike to figure out just how much I cut it down from its original 2950mm. I came up with 2670mm. Could 2500mm work? I’m sure it can for a normal Bullitt. When looking at my hose lengths, remember I had to re-route due to the battery box. This means the hose exits the corner of the cargo box and runs around (and is protected within) the concave rear edge of the honeycomb floor. It comes forward to the steering tube from the inner rear edge of that floor and only then begins its run up the steering tube. That adds several centimeters to the necessary hose length…

Which I didn’t care about as I had plenty of hose to start with. If I had only 2500mm to work with, I’m not certain I could have made internal routing work. Something for you to take into account and puzzle through when you do your own project.

Worth Noting

In my initial build, up front I was able to make the stock 2200mm hose that comes with the Magura MT5e brake kits work – and work pretty well. Look at the picture above and pretend you are seeing the stock black hose… I ran the cabling inside thru the cargo bay as you see above, and let it sit naturally along the lower edge of the floor (it’ll stay in the channel created by the edge of the honeycomb floorboard just fine). As it curves back up to the handlebars along the back of the cargo box, it did so in an arc right along the rear bulkhead. Flush to it. Nothing sticking out.

Fitment was fine, with nothing really extra but nothing stretched, either. The hosecame up along the rear wall, out of the cargo box along the extended handlebar stem and then to the brake lever. I added a couple of zip ties to keep it snug to other hoses and completely unnoticeable.

I ran the brakes this way for a couple of weeks while I waited for the longer cabling to show up, and I could have lived with it being like that permanently if I had to. However, if I had needed to raise the Easy Up to accommodate a passenger I might not have been so sanguine about this lazy solution.

Rotors & Pads

The choice of rotors to go with the MT5e’s is a little gimmick I really like. Generally bike owners shopping for rotors only concern themselves with rotor diameter. 160mm, 180mm, 203mm… those numbers sound familiar, right? But what about how thick the rotor is? Well, Tektro type 17 rotors are 2.3mm thick.

So what?

Your typical bike brake rotor is 1.8mm thick. Some brands will shave that down to as little as 1.4mm (Avid rotors were thin like this years ago when I was still using them). A thin rotor is lighter and thats nice for your skinny analog road bike. But a great big ebike? Not so much. You want meat on those rotors just like you want great big brake rotors on your race car. Brake rotors are heat sinks and braking is the process of converting momentum to heat. The more rotor you have the more heat it can absorb. The beefier and thicker your brake rotors are, the more it takes to warp them. Or for that matter wear them out.

My initial front wheel build used a 180mm Magura MDR-C rotor

So, one of the reasons I like Magura calipers is they are designed to take an unusually thick 2.1mm Magura brand rotor. Great. The Magura Storm HC rotor, or its new beefier cousin the MDR-C, are designed for the MT5e/MT7e, and vice-versa. These 2.1mm rotors are considered worn-out when they get to 1.8mm – thats the size most other rotors are sold new. Magura calipers should NOT be used with thinner industry-standard rotors. Thinner rotors extend the pistons too far and could cause them to leak. Do not ask me how I know this.

But what about thicker ones?

At last! We get to the point. I’m using 2.3mm thick Tektro rotors, which were originally meant for the small niche of downhill MTB bikes. Now they are sold by the boatload as ebike rotors with Tektro’s newfangled ebike brake kits.

Is 2.3mm too much for the Magura caliper? Almost, but it works. Since I have so many sets of Magura brakes on The Pacific Fleet, I can pull a set of partially used pads off of one of them, plug those still-usable pads into a new bike build, and let the slightly worn pads give me an extra skootch of clearance. When these pads have worn down and need to be replaced, the fat rotor is now worn a bit and can handle fresh pads easily.

I have yet to wear out one of these Type 17 rotors down to 1.8mm thickness, which is not something to complain about.

On the Front

So, on the front wheel the rotor is the 203mm size. Thats a lot of rotor for a 20″ wheel. I initially used a 180mm Magura MDR-C, coupled to Type 9 Performance (Black) pads. those are the ones that come with new MT5e calipers. I found this combo could easily lock up that poor little front wheel. I was already building another custom front wheel, so the final wheel build used a bigger 203mm Type 17 (even more stopping power, which is not so great) but with downgraded Magura Type 9 Comfort (Blue) pads – a lot less stopping power but great modulation and longer lasting.

My original – now backup – wheel is waiting in the wings with a Tektro rotor already installed. I’ll swap it onto the bike soon so I can take the primary motor apart and regrease it without disabling the bike in the process.

The pads were expected to be so much less aggressive that they would more than make up for the bigger rotor, and thats exactly what happened. I still have strong braking performance on that front wheel but now its very nicely modulated so I can clamp down hard without locking up the front wheel and making a spectacle of myself.

Since the Comfort/Blue pad compound is not sold in a Type 8 4-piece pad, I considered replacing them once they wore out with the Type 8S (Green) ebike pads. Still a step down from the Performance/Black compound, but the 4-piece pad config would step up the torque the calipers can apply to the rotor. Hopefully not too much.

That was the plan, and maybe it is something you want to try with your build. But the day I was to publish this post, I performed front wheel maintenance on the bike and saw the pads are down to about 1.5mm already – time to replace them in a couple weeks. The market is such that the Type 8 green pads are very pricey, and the Type 9 pads are dirt cheap from a German bike site. So what the hell I stuck with what I know already and bought 3 sets, along with another cheap Super Moto X tire (also very pricey if bought from a USA source) to soak up the $20 shipping charge and still keep me ahead of the game on costs.

On the Back

The rear rotor is, at present, a Magura Storm HC 203mm rotor. Its a solid choice for a rotor, and of course its the go-to until recently for a factory-matched kit. Why use it instead of the Type 17? Frankly it was in my parts pile and needed to get used up. So instead of playing the pad-swap game described above to fit a fat Tektro rotor, I put on a factory rotor and we’ll wear down the pads some thataway. After 1000 miles on the bike, it is already down to 1.9mm from its original 2.1mm. It won’t be long. Don’t blame the rotor: cargo biking is as severe of a duty cycle as you can get. I use the rear brakes as my primary stoppers with the fronts eased in after the rears engage. I get well-balanced rear brake wear as a result.

This 203mm rotor is taking a beating and will be replaced sooner rather than later with another of the big Tektro’s

Out back I am using the standard-issue Magura Type 9.P pads – the black Performance compound. Ordinarily I only use the Type 9’s initially as they come with the new calipers. I then replace with the more torque-y Type 8.P’s from then on. But here again I have Type 9’s in my parts pile so I am just using this bike to run through them. They work just fine, although to replace them or check pad wear you have to remove the caliper from its mount, which is one more reason why you want to use MT7 pads (a.k.a. “Type 8”) in your otherwise-identical MT5 calipers.

Brake Cutoffs

This bike has a Bafang mid drive powering the back axle, and a Bafang hub motor with KT controller powering the front. In my 2wd twin-hub-motor builds, I split the cutoff signal from one lever to both controllers on each lever, so actuating either lever alone cuts both motors.

I learned with the 2Fat build that trying this with a BBSHD and a KT hub controller bricks both motors – they never can start in the first place. I tried every kind of setting or workaround and they have to be entirely separate circuits or you get no motor power period.

Trying it again on this Bullitt build, a few years later: same result. The solution is for the rear brake lever to cut the rear mid drive and the front lever to cut the front hub.

One difference from the past is now, in 2021 I am able to buy a BBSHD wiring harness designed to use Magura’s red Higo/Julet plugs natively without messing around with finding or fitting adapters. Otherwise, you have to buy red-to-yellow Higo/Julet conversion plugs. Before the above direct connection wiring harness existed, I used these little jewels.


Thats it for the brakes. Lets talk about

The Front Motor and Wheel

Larry vs Harry Bullitt – the Battery (Box)

A big bike with two motors needs a big battery. Lets take advantage of the frontloader design to both hide and secure it.

The Bullitt Build
1. Battery and Battery Box (you are here)
2. Cargo Box
3. Brakes
4. Front Motor & Wheel
5. Rear Motor & Drivetrain
6. Bits & Pieces

Now there is a separate series on Bullitt II: hidden battery box. Onboard charger. Etc.

A big issue with an ebike – particularly one that is left outside on its own all the time – is battery security. The battery is maybe the most expensive component on an ebike and its a big theft target. So typically you have to carry the thing inside with you, and hey… thats a real pain in the neck. Not only is it a really heavy black brick, but you have to dismount it and re-mount it to the bike, and disconnect and reconnect it to the motor (forget about your display keeping the correct time and date), every single time. I have come up with my own way to make the best of this bad situation for my other cargo bikes, but with the Bullitt, we can make the problem go away.

The Kinda-Secret Compartment

Take a look at the picture above. See the big black box under the cargo area, near the ground? Thats it: the battery box. You’d be surprised by how many people don’t notice it. Even if they do, what are they going to do about it?

I had seen a few other Bullitt builds with battery boxes and they seemed like great ideas: The battery goes out of sight, out of mind under the floor of the bike. It lets you get creative on battery size (as in you can go bigger if you like since there’s lots of room down there). It may even be made secure enough that you can just leave it on the bike – eliminating maybe the biggest inconvenience of using an ebike for daily errands and shopping.

Also, just as with electric auto designs, a ‘skateboard’ config for the battery puts it centered and below the floor – down as low as it can go. That is as good as it can get for performance.

But I was thinking of none of these things when I was putting together my build sheet. I was still thinking I would do another quick-carry sling pack with the battery inside, and toss that pack into the cargo bay for easy removal and replacement. It wouldn’t be secured to anything but I would see about figuring that out later on.

My sling pack with a 20ah battery inside, used on my Surly Big Fat Dummy

But while the parts were still trickling in, I was participating in a discussion on the Bullitt Universal Owners Group on Facebook. Another Bullitt owner showed off his own build and mentioned his battery box – and that he had gotten it from Splendid Cycles – the same shop where I got my Bullitt frame and parts. I gave them a call and in short order one of the last examples they had on hand was on its way to me. I was told up front the box was a blank canvas, and I would need my own elbow grease to add mounting holes and any other refinements, such as waterproofing, cable exits etc.

As-delivered, the battery box looked as you see it below. A simple slot holds it up on the back. Its front at first seems unnecessarily complicated, but is quite clever. Its seamless, unbroken face prevents any direct channel for water ingress from the front, just behind the tire. The cutouts necessary to let the box slide into place doubled as my exit points for the power, charging and temperature sensor cables, so no need to cut any holes. It fits absolutely flush to the near side of the frame so no insulation is needed or wanted. Its shape is angled on one side to clear the steering tube.

The box as-delivered, almost. I used black flexible silicone sealant to all the internal seams, and dabbed over all of the rivets as well.

Box Installation

The first step was to drill the box so it could be fixed in place. As-designed, it would stay put. But I am sure there would be some shifting and rattling… and I can’t abide rattles. Also, the existence of the box complicated the installation of the honeycomb floorboard. The floorboard expects to be able to drop a bolt straight down and use a nut underneath to lock it down. Well, now that bolt hole is completely inside the box on the front left corner. Its outside on the right front, but not by much. I needed to change those two mounts to fixed studs going from the bottom up.

I also wanted to add an entirely separate bolt on the front dedicated to strongly fixing the box in place. I decided to use an oversized hole, and used a hand file to enlarge it to a rectangle. Following that, a combination of an oversized, hardened washer and a flush-fit M8 bolt gives a flat fit that works under the honeycomb board fitting directly down on top of it.

The new ‘studs’ are common, long M6 socket caps with – get this – a Presta valve nut to hold them in place. I needed a low profile nut and there’s nothing lower-profile than the common presta nut, which even fits snugly inside the bolt hole manufactured into the LvH honeycomb board.

Forward box mounting complete. Two studs are ready for the honeycomb board, and the center bolt holds the box tight to the frame.

For the rear of the box, to match up with the honeycomb board’s rear mounting hole, I had to use another M6 rather than go with another big M8. I drilled a thin hole thru the box’s top flap and the honeycomb board’s rear mounting bolt goes thru there. However to be consistent – because I wanted to use security nuts to make getting into the box that much more difficult – I made it go in from the bottom-up like the others (we’ll show those security nuts etc. in more detail when we talk about the cargo box installation).

Now Install The Battery

At this point, the next step in the installation process – which, maddeningly, has to be done in this order whether you like it or not – was to install the battery.

You can see how I accomplished that below. All of the padding is closed-cell, and I left as much of the battery untouched by foam as I could. The battery lays on the bare alloy of the box with no padding (a solid metal wall is plenty of protection). It is surrounded on four sides such that it cannot move, even after months of pothole pounding commutes and store visits. I disassembled the bike after 500 miles and looked inside to be sure of this. No water had gotten in either despite riding in rainstorms.

There is a brake cable braze-on above the pack underneath the center bar. It is perfectly positioned to smash into the cells underneath if the pack bounces up to meet it. I prevented this possibility via some left over Minicel T600 EVA foam (you’ll see what I used it for in the Cargo Box episode) to fix the battery in position (i.e. keep it from bouncing). Two pieces are used, one on each side of the braze-on. Underneath this area the visible green rectangle is a piece of thin metal fence strapping which provides a last but certain line of defense against that braze-on ever contacting the bare pack.

The battery is literally incapable of movement on any axis. It is held solidly – but not enough to smoosh anything. Rapping on the box with your knuckles yields a satisfying thunk as if you are rapping on a solid block of metal.

Notice the short extensions in the pics above? There are two lengths of them in use (strictly speaking there are three as we need two when we split the power to run to both motors). I don’t like to make direct connections to wiring that is a hassle to repair – like wires that run hot directly from the battery. I want to be using a short extension on each side of a connection for two reasons. 1: So the wear and tear occurs on something that is easy and painless to replace if it wears out. 2. If something terrible happens like a short, the melted connector is on an extension and can be easily unplugged, thrown away and replaced. No need to be working on live wires to salvage the battery (assuming a short doesn’t cause other problems with the pack itself).

I have had one occasion where this saved my bacon when an XT60 extension shorted on a water bottle bolt head. There was no damage other than to the destroyed cheapie extension. In this case, there is no issue of frequent connects and disconnects, but the habit of using extensions for the safety angle is hard to break.

Lets Talk About The Battery

An AWD bike needs a lot of power. Even one where I have toned down the power to civilized levels. You must have a pack whose Battery Management System is strong enough to run two motors at once, and if you get into the subject and learn the specifics, you will find out real fast that commercially-manufactured battery packs can’t cut the mustard (this is why commercial AWD bikes have two separate batteries). If you want to build the bike right as opposed to building it cheap and sucky, you have to get yourself a custom pack built that is tailored to the job.

Pack Details

The battery itself was built custom to my specs after some discussion with Matt Bzura at Bicycle Motorworks. This is one of several packs I have purchased from his firm, after hearing nothing but good things about his work from other builders over the span of a few years. I’ve had nothing but good experience working with him as well.

I knew that an AWD bike needs more power, so the battery pack needs to be bigger than usual. And the Splendid Cycles battery box is a big sucker. If I put in a battery that filled that box it would be TOO big. Looking at the box dimensions and knowing what I wanted to do for crash padding gave me one half of the picture. Matt @ BicycleMotorworks filled in the blanks with the dimensional details of the cells and battery management system chosen for the job.

Cells Samsung 40T (21700’s)
Pack Config 14S8P (52v)
BMS Capacity 70a Continuous output
Amp Hours32
Output CableXT90S / 8ga
Charge CableXT60 / 12 ga

The 40T cells in the larger 21700 size, and overall pack design allows it to operate under load without voltage sag, and without heating up, despite the enclosed space and the dense, closed cell padding that holds the pack fast. A temperature sensor is attached to the pack top and runs outside of the box for easy visibility from the saddle.

What About Heat?
In use in a normal climate – bearing in mind its sealed in a big metal box – the pack does not get noticeably warm over and above ambient air temperature – nothing over 5 degrees Fahrenheit above ambient. However, 5 degrees over ambient is a lot when its 105 in the shade, where in the sun, the pavement is radiating heat at 130. In severe heat (as I write this, the end of next week is scheduled to reach 114°F, which is more than 45°C) I need to plan ahead for where the bike is going to be parked, and plan my route to provide the shortest, shadiest path to my destination. Our local area has already experienced several days where the temperature has exceeded 110°F / 43°C. Even though the battery cells are not thermally coupled to the case, I ringed the box with heat sinks to help keep the pack a bit closer to ambient temperature. They have reduced pack surface temperature by up to 5 degrees.

The battery charge cable is routed outside of the box along with the power cables, and comes up as shown in the photo below (the green plug). This plug is semi-rigid thanks to the manner in which I insulated the end connector, as well as how its braced against other secured wiring. It is easy to access, protected from the elements via the plug cap and not going anywhere. In winter months a rubber band and some plastic will ensure nothing can get through and cause any fireworks.

And last but not least… this is a 52v battery that has a capacity of 32 amp hours. I like having batteries big enough that range anxiety doesn’t exist. You simply go ride the bike and do what you need to do. Considering the bike – thanks to its motor configs – eats only 400-500w at cruise… my ass will wear out in the seat before the battery charge does…

So long as I remember to charge it. But even then – and this has happened to me already – the battery is big enough to maybe rescue me from that faux pas.

The battery temp sensor sits here, without any need for actual mounting. The Bullitt’s ride is so stable nothing more is required. The charger plug is covered in a green cap at center.

Thats about all I have on the battery and battery box. We’ll stick to the same area of the bike in the next article in the series, as the two are linked together:

The Cargo Box

The Bullitt, by Larry vs Harry – Cargo Bike Build

And now for something completely different. The Bullitt from Larry vs Harry is a bucket list bike I love to ride. This series will cover the details of a frame-up build that includes AWD electric assist.

The Bullitt Build (you are here)
1. Battery and Battery Box
2. Cargo Box
3. Brakes
4. Front Motor & Wheel
5. Rear Motor & Drivetrain
6. Bits & Pieces


Take a deeper dive into the benefits, whys and wherefores of assisted AWD on this bike here.


Originally, this was going to be a single article that covered everything. However, as time progressed and I got more and more of the details written down, I found I was at almost 6800 words, and could easily hit 8-10,000 before completion. Thats too damn big, so it had to be broken up. This opening post will cover some of the introductory bits. Then we’ll split off into followups that hit the high points of the various things worth bringing up.

There’s a lot to get to so lets jump in.

Background

Having built up the Mongoose Envoy as my first cargo bike, then supersizing to the Surly Big Fat Dummy, you would think the Larry vs Harry Bullitt was my third choice for a cargo bike. It was the opposite: The Bullitt was my first choice. But first,

What the hell is a Bullitt?

A Bullitt is a bakfiets. How does me saying that help you? It doesn’t, until I add that bakfiets is a Dutch term that means “box bike”. You’ll be helped along a bit more by the fact that a bakfiets is often referred to in English as a ‘frontloader’. So, the box is in front of the rider. Here is a Google image search that will let you see a slew of them, of all different types.

Looking at all those different pictures, they all look sort of like 2- or 3-wheeled dump trucks. Not exactly a fun ride. But thats to be expected of freight haulers, right?

So, What the hell is a Bullitt?

A Bullitt is a frontloader-style cargo bike made by Larry vs Harry in Copenhagen, Denmark. It does its cargo carrying job, but its also specifically designed to be nimble, on a frame that is relatively rigid. Its also meant to be those things in a lightweight package, where that frame is lightweight alloy (whose inherent rigidity is mitigated by the sheer length of the frame. A Bullitt is also a very comfortable bike to ride).

In short, the Bullitt is a cargo bike for people who still want to have fun riding their bike. You aren’t schlepping around in the bicycle equivalent of a minivan.

This gets the idea across in 1 minute.

When I originally decided to build up a Bullitt, I set up my build sheet and began listing out components. But before I finished, the cost crossed my pain threshold and I chickened out. This was going to be my first cargo bike. I had no experience with the platform, and wasn’t even sure I would like the idea, never mind throwing in the funkiness of a frontloader. I wasn’t ready to make such a big financial commitment.

So I went the budget route with the Mongoose Envoy. I used that frame and fork as a donor platform to develop a really nice lower-cost cargo solution. After some use I decided 1)this whole cargo bike thing was really cool and 2)the Envoy wasn’t big enough for the XXL jobs I wanted to give it.

When I was doing my research prior to buying the Envoy, I had almost bought the much larger Surly Big Fat Dummy, but bailed on that one too due to the same kinds of newbie uncertainties that led me to bail on the Bullitt project.

So, wanting to upsize, I went there next. That bike has been a thing of beauty. I loved it and still do for a variety of reasons beyond its utility as a cargo bike (and a bikepacking bike. And a take-the-trails-route-instead commuter. And an unstoppable freight train that terrifies all who cross its path). The Big Fat Dummy truly is a BFD.

But…

Using the BFD for all things, every day, I could see room for improvement. Stuff that bugged me and worse – slowed me down.

At the shops, you have to bring the battery in with you or risk getting it stolen. I had a solution for this but it still takes effort to deal with and is a pain. Additionally it limits the size of the battery as the bigger it is, the more trouble it is to carry around.

The BFD has two panniers that hold more than 275L (not 27.5… Two Hundred and Seventy Five). Who can ask for more? Except bags that big aren’t kept opened up and ready for use. They’re folded up and strapped to the frame. Expanding them requires some fussing and fiddling with the straps. Not the end of the world but it has to be done. And then you need to cinch those four to six straps down to secure the load. And balance your load between the bags or bad things can happen. When you are doing this every day at multiple stops, you start wanting things to be easier… but how?

Enter The Dragon

A Bullitt from Larry vs Harry. Thats how. A bike purpose-built for a narrow type of use-case: urban utility. The Bullitt is the most nimble and rigidly-framed of the genre: the sports car of the frontloader world. The battery on this bike will be locked in a quasi-concealed, sealed box under the cargo floor of the bike; out of sight from prying eyes and prybars. No more lugging it into the store with me. Most importantly, the bike has a floor in the first place. Cargo is held in a great big open box. I can just walk up, dump my shit in and and take off. No more pre-flight prep.

Also I kind of liked that it looked weird… and I had no idea whether I could ride such a contraption. I don’t get that kind of uncertainty with bikes much these days and I looked forward to the challenge.

Oh, and since LvH decided to call the green paint on the bike Lizzard King, well that makes for an obvious name for the bike.

Bullitts are – wonderfully – built up from frames and customized by a great many of their owners. So even though I am doing a lot of writing-up here, there’s not much point in doing full how-to’s, since thats how most everyone does it already, anyway. So my focus will for the most part be more of a high-level one rather than getting down and into the finer details of Tab A inserting into Slot B etc.

What a mess! A month or so after initial build completion my custom battery arrived… time to take it back apart!

So Lets Build It Already!

So much going on… Where do we start?

The Frame Kit

Your local Larry vs Harry dealer will happily sell you a complete bike, or even one whose frame has been purpose-built to integrate an electric motor. You can choose an internally geared hub, and the frame has a split in it to allow a belt drive. Lots of options for a complete bike, or buy their frame kit and build your own.

I chose the frame kit route. The kit comes with the frame, fork, steering arm, headsets (plural) installed and a number of other components that are unique to a Bullitt’s construction, so you don’t have to go searching all over creation for weird parts. I also purchased the “honeycomb floor board” (the cargo deck) and the “side panels” (hard sides to the cargo area that turn it into a big bucket). It all arrived in one giant box, too big for UPS so it was a LTL freight carrier in a full sized semi-hauler that brought it in. The truck was so big it had to meet me on the street.

I purchased the frame kit from Splendid Cycles up in Portland, Oregon. I handled the transaction entirely over the phone and the folks at Splendid were both helpful and generous with their time, answering my technical and build questions and making sure I was taken care of. Delivery was prompt and I was frankly amazed at how well the frame was packaged once I got the box opened up. Oddly enough I met the tech who packed my frame online, in the Bullitt Facebook group, who was happy to see I got the frame and confirmed what was visually obvious: he had spent time making sure it was packed well so it would get to me in the same shape it left their shop.

All Wheel Drive

Even though the bike only took me about a month to build so it was at least roadworthy, there was a lot going on with this bike. Most of the reason it was such a pain revolved around this one feature. In the end, it was worth it, but the added complexity of an AWD ebike is not for the faint of heart.

Two-motor AWD means wires everywhere. Hiding them is something of an art form.

I have built several all wheel drive ebikes, but not recently. I decided the Bullitt was going to be the proof-of-concept behind a different, more civilized/everyman form of ebike AWD that I had been mulling over for years but never did anything about. That subject, the merits of an AWD ebike and the specifics surrounding it are all dealt with in a separate case study in my dual-motor AWD ebike series. I’ll let that post and its companions stand on their own and just say that the sort of cooperative, drama-free AWD that was put into the Bullitt is, in my estimation, a tremendous success with regard to making it a viable all-day, everyday auto replacement.


Which leads us straight into the next episode:

The Battery (and Battery Box)

Dual Motor AWD Electric Bikes – Case Study: Larry vs Harry Bullitt Cargo

After multiple strong AWD builds, I used this one to prove a unique concept: You don’t need big power to get big AWD benefits.

AWD Ebikes Menu
AWD. OMG. WTF!
Case Study – Flatland Fat Bike Commuter. Hub+Hub
Case Study – Alpine Road & Trail. Hub+Mid Drive
Case Study – Low-Power Cargo Beast. Hub+Mid Drive (you are here)

The Lizzard King

  • 500w, 25a geared Bafang G020 front hub motor
  • 30a BBSHD mid drive (rear motor)
  • 52v, 32ah single battery, skateboard config (box under cargo floor)
  • KT and Bafang displays
  • 160 Nm rear, 45Nm front


Want to see all the details of how this bike was built?

Go here to see that separate series of articles.

My previous AWD builds all used effectively the same front wheel setup: A 35a controller mated to a Bafang geared fat motor packing an 80 Nm punch. It was so powerful, on my early commuter bikes I needed to turn down acceleration via a slow-start setting. When I graduated to a combination mid drive+hub, I found best results on rough trails came from the same slow start, but also using the front power sparingly: little if any throttle and gentle PAS.

There things stayed for a few years – roughly from the middle of 2017 to early 2021. During this period I concentrated on riding and refining the use and configuration of these AWD bikes. I built other bikes during this time- all more traditional single-motor mid drives. As part of that work I came up with tuning settings that worked very well with pedaling and a cycling mindset. These changes worked great with the 2Fat AWD bike as well.

With regard to tuning, I concentrated on backing off the BBSHD’s power when delivered in ‘pedelec’ mode: limited use of throttle and pedal assist only. The point of this was to have a bike that did not run away from me, still delivered measurable, useful levels of assist, lacked the common complaints against cadence-type assist and did not suffer from any of the weaknesses of torque-sensing.

When 2021 arrived and I wanted to build a bucket-list bike – the Larry vs. Harry Bullitt cargo bike – I decided to go all out and make it AWD. Further, I wanted to prove a concept I had been mulling over for the last few years. For lack of a better term, lets call it Drama-Free AWD: Not a hot rod, but what a normal person who just wanted a reliable automobile replacement would want to ride.

Ingredients

Its a pretty short list:

  • Low power
    High power in a front wheel can be fun, but its not necessary to gain the traction benefits that come with AWD. Use a smaller, lighter, relatively low-powered motor (45 Nm vs. the prior 80 Nm) as part of its design. Also use a smaller controller that peaks at 25 amps rather than the previous 35. Continue to use the slow-start setting to ensure … Drama Free AWD. 25 amps on a smaller diameter wheel will still be a strong assist, but those amps will be rolled on slowly so no surprises.
  • Fast Wind Front Motor
    The Bullitt has a 20″ front wheel. A ‘fast wind’ motor favors torque off the starting line at the expense of higher top speed. This is normal for a small wheel build and further solidifies the emphasis on slow, strong startup power that melts away on its own as speed increases.
  • Toned-Down Rear Motor
    My revised motor settings keep the BBSHD from engaging until speed reaches 6 mph (9.7 km/h) if I rely on pedal assist. I learned how important that is to drivetrain longevity when I built 2Fat. We’ll re-use those identical settings.
Since this picture was taken, I switched the big flat Catalyst pedals for Funn Ripper SPD pedals, and I cleat in.

What I Expected

On a bike destined to carry heavy loads, the front motor is intended to get the bike off to a painless start. It does this job very nicely. Despite the relatively low power, it still gets the bike rolling from a stop, and effectively takes out the BBSHD’s shock to the drivetrain when that second motor kicks in at 6 mph (9.7 km/h).

That reduced sting will translate into reduced wear and tear, and reduced parts replacement over time. Its too early to pull hubs apart and look inside to verify this assumption, but since I have seen and verified the effect before on similar hardware, there’s no reason to assume different results.

UPDATE: June 2022
Over 1800 miles / 2900 km later, I am still using the original chain. At about 1300 miles / 2100 km, a check on the rear cluster and cassette (upgraded to the steel DT Swiss body) showed barely any discoloration on the cassette surface… never mind any wear.

It was a short list of things to expect and… it all panned out. But there were also some pleasant surprises. This turned out better than I thought it would.

What Surprised Me

I noted above the motor is ‘fast wind’; built for low-speed torque, not high speed rpms, and how this plays into the smaller front wheel size. Intellectually, thats easy to understand. Less obvious was the fact that, in practice, there will be a lot less motor usage than there was before.

With The Great Pumpkin, I usually run both motors at equal levels (usually full blast) all the time. The bike and flat, straight streets just lend themselves to a high speed cruise. Two identical motors and identical controllers gulping juice from one battery mean a big power drain. No surprise.

With 2Fat, while I reduce power to the front motor, I was often giving the bike hard use on trails. More often than not the bike is fighting its way up a hill, thru a bunch of sand etc.

So even though The Lizzard King is not dramatically different than 2Fat in terms of its configuration, the world it lives in is quite different: level and smooth city streets. Easy acceleration and long periods of the motors spinning fast while running at an efficient cruising speed.

More different still: Off the line, the front motor kicks in slowly and then power melts away as wheel revolutions increase. It pulls strong from zero to about 16 mph. But from 17+, it starts scaling back as the motor approaches its rpm limit. By the time 20 mph rolls around, on typical level 2 assist you are down to about 200 watts of output. By the time you hit 23-24 mph on flat ground, wattage to the front wheel has minimized to a steady… 38 watts. Just enough of a dribble to ease the wheel’s free spin.

If you hit an incline, you’ll slow down a tad and see wattage output creep up again. But rolling down the street on the flats, the front motor takes itself out of the picture. Its time for…

… The rear motor to kick in. As noted, pedal assist does not engage the rear motor until it reaches 6 mph. So when the front motor is eating the most juice, the rear motor hasn’t even started. As the mid kicks in and spools up, the hub begins making its graceful exit.

The two motors never really run hard together at the same time, unless climbing a hill (or I force the issue via using the two throttles). Then you can see watts climb on the front rather than fading away. Cruising at an energetic cadence around 24+ mph , you are on the single rear motor, being given a small boost from the front motor (remember those 38 watts?).

With the two motors staying out of each others’ way, this translates to an overall reduction in expected battery drain, consisting of both reduced peak and continuous draws. It gets better though.

Much Better!

The rear BBSHD is also using a lot less power than its siblings in The Pacific Fleet.

At 20 mph, on PAS 2 in the front and maybe PAS 4 or 5 in the back, looking at both displays, I can see 250-300w being output from the rear motor, and another 150-200w being output from the front. 500w or kess are being drawn between the two motors, on a great big cargo bike. All the way up and down the speed curve, watt and amp output for the BBSHD is much less than it is on any of my other bikes.

Not So Fast!

All of this wonderfulness is only true when running under pedal assist. If I mash the rear throttle the BBSHD will, as usual, peg the output gauge until I release. And that means it will burn thru my battery range lickety-split. Not a surprise. There is no free lunch in this world, but if we stay off the throttle we still get a hefty discount.

And I still configured my big single battery (custom-built for this bike) to the usual theoretical limits: A 25a peak front controller and a 30a peak rear controller mean I must have a battery management system with a bare minimum of a 55a continuous rating, and preferably 60 (mine is 70). I would rather not take any chances, but clearly I have a bigger safety margin than I figured on originally.

And despite the capability of the bike, reality is it rides more comfortably around 20 mph. So power consumption is lower still simply because of the type of bike it is. But the big takeaway is its lower power use is lower across the board. It was an unexpected gain in efficiency, but looking back on it, it should not have been. The benefit was hidden by my hard use of the other bikes.

Commercial Manufacturing

Should a commercial bike be made with this Drama Free AWD kind of approach in mind, a thoughtfully designed system could manage power in such a way as to map out the curves on the individual motors. Develop something that never bumps into the limits of a much more conventional BMS. That makes for a battery system less expensive and easier to source in volume. And a street machine is going to have lower power needs than is generally understood to be the case with an AWD bike.

Lower power means safety for the casual rider, lower cost and smaller battery sizes.

Lower power on a street bike could look like – in the USA at least – dual motors fitted to bikes that still remain legal within both federal manufacturing standards and individual state vehicle codes. A 249w front motor and a 500w rear for example. Or even a 250/350.

Whats the Takeaway?

The fact that I can operate a great big bike like The Lizzard King at power levels well below allowed USA ebike power limits is testimony to the fact that viable, useful AWD can operate well within the legal framework of ebikes in this country.

Just because you have two motors does not mean they both have to be running simultaneously at full blast. Turns out… not doing that can be kind of a big deal.

Dual Motor AWD Electric Bikes – Case Study: Fat Trail and Hill Climber

Built to conquer the weakness of twin hubs in hills – and eliminate the damage a mid drive does to an ebike’s drivetrain. The bike I call 2Fat did all that.

AWD Ebikes Menu
AWD. OMG. WTF!
Case Study – Flatland Fat Bike Commuter. Hub+Hub
Case Study – Alpine Road & Trail. Hub+Mid Drive (you are here)
Case Study – Low-Power Cargo Beast. Hub+Mid Drive

So, my Gen 1, 1.5 and 3 bike layouts are all twin geared hub designs. What was Gen 2?

2Fat

  • 750w, 35a geared Bafang G060 front hub motor
  • 30a BBSHD mid drive
  • 52v, 12.5ah rear motor battery in triangle
  • 52v, 12.5ah front motor battery on rack top
  • Batteries connected in parallel to form a single ‘virtual’ 25ah power source to both motors
  • KT and Bafang displays
  • 160Nm rear… 80 Nm front (do the math on that one!)

I live part-time in two towns: The first, an extended work visa, is in Fresno California, smack in the middle of California’s San Joaquin Valley and flat as a table. I built The Colonel, The Purple Thing and The Great Pumpkin for commuting in Fresno.

While I most often take pics of it in a wooded area, 2Fat is just as happy on paved, hilly roads. Shown here with front panniers, its 4-bag carry capacity makes it a quasi-cargo bike.

After a fashion, I finally was able to get a big enough bike rack on the back of my SUV to bring the Colonel to my actual home in Pacific Grove, California. My house is at the top of the hill there. Unlike in Fresno, nothing in or around the area is flat. You are either going up a steep hill, or down one, or both.

My intention was to be able to use the Colonel like I did in Fresno, as local errand transport and a light duty cargo-shopper. Unfortunately, I found out the first day about the limitations of hub drives: They suck in hills.

Hubs are Single Speed

Hub drives power an ebike via the axle. They don’t – and they can’t – use the gears of the bike. Forcing a single speed hub motor up a hill makes it just as miserable as a human stuck with no gears. So even though I have very powerful hubs, and they were geared hubs that put down the most torque of any on the market… they still struggled. Even with two of them. I could hear the gears groaning inside the motor casings and I could tell that, while I could get up the hills, my motors were not happy about it. I did not want to lug them into an early grave. I had already gone to a lot of trouble to make the bike bulletproof and had no desire to ignore the problem and inevitably kill it.

These twin 80Nm hub motor wheels were on The Colonel in 2017 at the time of my first hill country ride (above). Now they are on the Great Pumpkin.

The solution?

I Need To Build a New Bike

Everybody knows mid drives are the solution to the hill problem for an ebike. A hub motor is single speed and at least relatively weak on torque, but a mid drive uses the gears in the drivetrain, plus it has double or more the torque output of a hub, and thats before you factor in the multiplier of the gears. Wonderful right? Except mid drive motors – especially DIY builds – are notorious for putting drivetrains into an early grave. Why? Well because they pour a LOT more power through the chainring, chain, rear cluster and cassette body (i.e. “the drivetrain”) than a bicycle was ever meant to withstand.

  • A normal cyclist can pump out maybe 300 watts for a minute or so, but typically normal sustained – strong – output is about 100 watts.
  • A professional sprinter/mutant is capable of pumping out almost 1000 watts, but only for about a minute or two. Thats not enough power to make a slice of toast.
  • EU-market electric motors must peak at 250w of output to stay legal (pssst… they don’t).
  • A 25-amp BBS02 on a 48v system puts out in excess of 1250 watts peak
  • Your garden variety 30-amp BBSHD running under a 52v battery is peaking – and can sustain – about 1750 watts of output.
My rear rack trunk battery. The capped red wire is for charging. The black wire on the rack stay is power output to the front motor. This is the original dual-separate-battery config

That gives some perspective on how much abuse is heaped upon a drivetrain with a mid drive. Coming off the successful builds of The Colonel (v1.0) and the Purple Thing (v1.5), I knew AWD reduced load on the individual motors dramatically when they work together as a team.

Given that, I thought about how I could use a front hub to reduce or eliminate the shock that a mid-drive puts onto the ebike’s drivetrain. Not only would I gain the traction benefits of AWD, and the benefit of reduced load from the team effort – things I already knew were a big positive – the front hub would also, if used in a slightly different way, provide an important added benefit: eliminating all the extra wear and tear that goes with having a mid drive.

If it worked, it would give me a bike with all the original AWD performance benefits, plus the ability to effortlessly climb walls, without tearing the bike up.

SPOILER ALERT: It worked unbelievably well.

New steel on the right, used alloy (1000 miles of use) on the left. And this was WITH AWD to reduce the wear and tear. Ordinary single-motor systems with this mileage would be dramatically worse. Substituting the steel body eliminates all wear.

In fact this bike is a showcase on how AWD can almost eliminate mid-drive wear and tear. Making a bike that climbs hills and bombs trails really well is almost an afterthought.

So that is what I am going to focus on here in this article. What was built and how was it used?

The Build

Briefly, this bike is the Great Pumpkin on the front wheel, and a typical mid-drive installation on the back. In between is the usual extra wiring scattered all over the place to deal with powering two motors, set up dual PAS etc..

The Front Motor

2Fat has another Bafang G060 80Nm front fat motor installed – this time its inside of a custom-built 100mm double-wall Weinmann (branded as an Origin8) rim. Go fat or go home. Attached are the same two torque arms as seen on the Pumpkin’s installation, and once again the controller is sitting in a grommeted handlebar bag that doubles as a wallet/keys/phone holder. It also serves to disguise the uncut steering tube I used to give me a more upright – but not too upright – riding position.

Another big, fat, 80Nm front hub motor. This time laced into a 100mm rim. Because fat bike.

Different from the Pumpkin is the battery setup. This bike was built before the v3.0 Pumpkin came onto this Earth (The Purple Thing had just been born). So, lacking the wherewithal to commission a big custom battery for the triangle, I used two packs, one for each motor. The front motor’s 12ah 52v battery was located in the rack trunk at the back of the bike. I had already learned I did not want to put a battery on the front rack as it made the steering too heavy. The rear motor’s 17.5ah pack was in the triangle.

It could be worse: Tucked in between the panniers in the rack trunk is one of two batteries. The second pack is in the triangle. Whats on the front rack? A weatherproof, adjustable 5a charger.

Additionally, due to the very low standover of 2Fat’s Large sized frame thanks to its top tube (it is a titanium, USA-made Chumba Ursa Major) there is not enough room to plug in a properly big battery in the triangle to handle both motors. So I had to do two batteries and live with the awful choice of putting one on the back rack.

After running the two dissimilar, separate batteries from its initial build in 2017 to March 2021, I switched to two identical, now-parallel’d-together packs in the same locations. Each is 12.5ah (14S6P) with Samsung 25R cells. Each has a 50a continuous BMS. As such, the system has a single 25ah power supply with a BMS capable of handling 100 continuous amps. Considering I can never peak past 65, I’m in great shape. I purchased the packs from Bicycle Motorworks, who builds their packs in the USA and constructs them at time of order.

Sidebar:
Running battery packs in parallel should only be done by those who have done the research and know exactly what they are getting into. In this case, both packs are identical, being manufactured to-order together, and have the same charge cycle count. Their voltages were matched before they were joined and there is some additional babysitting that will be necessary for charging and balancing. If you can avoid running packs in parallel and use just one battery: Do that instead.

Using two entirely separate batteries is a kludge and your last resort. Not only will you have to charge them separately, you will also draw down the two batteries separately at different rates which will result in uneven remaining power, lesser range and more frequent recharges.

The Rear Motor

This is pretty much your garden-variety 52v BBSHD installation. It has a couple of nice spiffs in the form of a 42T Lekkie Bling Ring, and Lekkie Buzz Bars, but neither of those things are a requirement of the AWD approach we’re discussing here.

The rear wheel is another matching Weinmann 100mm rim, again with DT Champion 2.0 spokes and 16mm brass nipples. The rear hub is a DT 350 Big Ride, which has sealed cartridge bearings and has been upgraded to a steel cassette body. Additionally a 9-speed Shimano HG400 cluster gives me steel cogs literally welded together into a single cluster, that spreads the enormous torque of the BBSHD across the entire steel cassette body. The DT350’s ratchet engagement mechanism is one of the few known bombproof rear hub mechanisms when faced with the power of the Dark Side 30a BBSHD motor.

A solid rear wheel build with extra strength parts throughout is crucial to a successful mid drive ebike.

205mm front and rear rotors with Magura MT5e brakes

The Special Bits

There is a bit more that went into making these motors work together. The complete integration possible on the Pumpkin thanks to the use of identical motors and controllers wouldn’t work here.

Brake Cutoffs

Trying to share cutoff signals between the motors again – using adapters for the red-to-yellow connections found on the BBSHD – resulted in bricking both motors. I tried everything to share the signals. It can’t be done unless you are willing to install a second, independent set of hydraulic magnet style cutoffs, zip tied to the integrated MT5e cutoffs and connected via a ‘y’ further down the line. That would work but it would look like crap, for very little benefit over what I ended up doing: I set up the front brake to engage the front motor cutoff, and the rear – with a red-to-yellow HIGO adapter – to cut off the rear motor. Since I always use both levers to do my braking I get an effective result.

Pedal Assist

PAS for the BBSHD is built into its motor casing, so it just works. PAS for the front motor was another matter entirely. Ordinarily the assist disc and sensor runs on the right-hand, drive side of the bike and hides behind the front chainring. This is not possible with the BBSHD’s secondary gear housing being there instead. So PAS had to be made to work on the left hand side. The KT controller has left-hand PAS sensor installation settings.

What was needed then was a left-hand install. This was quite a bit trickier, since the 120mm motor running in front of 5″ tire-compatible chainstays had zero extra spindle length to mount the disk. Lacking a bottom bracket cup to mount the PAS sensor ring, I set it behind a second inner lockring – I used two inner lock rings stacked like jam nuts rather than the usual inner+outer ring. These doubled inner rings had the secondary benefit of being a more aggressive, solid mounting for the motor.

With the sensor mounted, next I had the sensor ring to deal with. As noted above… there was no length available period for the sensor disk as the crankarms mounted pretty much flush to the bottom bracket.

The eventual solution involved hogging out the center of the PAS sensor disc so it could sit on the inner flange of the Lekkie crankarm instead of the spindle. I prepped the crankarm with… thin strips of thick duct tape so the disk would sit tightly on the flange. It was a bodge but it worked, and with just one improvement since installation in 2017 it has held perfectly. That improvement is a zip tie to help hold the disk steady in position (of course I used a zip tie. We have duct tape in the mix; all thats missing is a zip tie).

Worth noting: I used this identical PAS ring mounting when I built the Lizzard King AWD cargo bike in 2021. Not only did I have enough extra spindle so I did not have to do this surgery on the ring, I also realized I could unscrew and reverse the sensor in its mounting ring. This eliminated the need to use the reverse settings in the display/controller. Since the inset ring was reversed, it was outset now… and that held the sensor closer to the magnets (they work fine inset as seen here, but closer is better).

The Cockpit

Here’s where the eagle-eyed may spot a preview of how I ride this bike to soften up the mid drive.

Those are Jones SG bars with ESI XL Extra Chunky grips, wrapped in silicone tape

On the right, we have the grip, then the brake lever, followed by the 9-speed shifter. Here again we see a v2.0 feature that v3.0 fixed: A SRAM drivetrain gives us a SRAM, not Shimano shifter. The Shimano shifter needs so much real estate on the grip it is impossible to put a throttle on that side of the handlebars. Look at the cockpit of The Great Pumpkin and the Lizzard King to see how a SRAM shifter solves this and lets me do one throttle per thumb.

Being unable to do that at the time – and believe me I tried EVERY possible combination of throttles. I still have most of them in a box in my garage. I settled on two styles of thumb throttle, side by side on the left, with the innermost throttle being for the hub/front and the outermost for the BBSHD/rear. As for the eagle-eyed part: The front throttle is cocked higher so between that and its longer throw, it is engaged first and when at 100% it follows the natural curve of my thumb. Both throttles can then be at 100% and my hand stays comfortable at WFO.

How To Ride It

At last we get to the point!

I already let the cat out of the bag earlier: The biggest deal associated with this bike is not that it can climb really well (REALLY well). Nor is its ability to handle trails and rotten conditions its star quality.

2Fat was made to get dirty

No, the real point of having a mid drive teamed with a front hub motor is to use that hub motor to take the shock off the drivetrain that mid drives deliver. Do that and you also take away the excess wear and tear on the parts (if we are being fair, a lot of this comes from doofus riders who don’t know what they are doing).

When starting, start with the hub

This is most of the deal right here. Don’t make the mid drive haul the bike up from a dead stop. Its got the torque to do it. But everything takes a beating in the process. The nylon gears inside of the mid drive. The chainring. The poor chain. The suffering cogs. The cassette body being dug into by the cogs. The pawls inside of the cassette body that are straining against the hub. Your ebike hates you for doing this to it.

By using a mid-drive-strong chain, a steel cluster and a steel cassette body with a ratchet engagement mechanism, we harden the drivetrain to be very tolerant of this abuse. Between that and learning how to use a mid drive, wear and tear really isn’t bad at all. Maybe no worse than a quality analog bike used hard. But still… even with the hardened drivetrain it sure would be nice to take things easier.

By using a hub motor to get the bike rolling – even by just a few mph – we accomplish this mission. Using my pedaling-friendly BBSHD programming or something like it, the BBSHD will not kick in on pedaling until the bike crosses about 5 mph. So from a stop, you hit the front throttle for about one full second. That throttle is cocked up a bit higher on 2Fat to make that a natural move. The bike starts up from its dead stop without any strain on the drivetrain since the BBSHD is not even running. Simultaneously, you also start pedaling. This engages the cassette mechanism.

When speed crosses 5 mph, the BBSHD’s pedal assist now kicks in on a drivetrain that is already engaged. There is no longer a risk of having the motor jerk the chain and smash the cluster into engagement. And with this gentle engagement, the motor starts working on a bike that is already moving. So you get the doubled benefit of a lighter effort against all components to get your fat bike off its fat ass. Instead, you get smooth – and strong – acceleration. The lack of lugging the motor has the further benefit of not generating anywhere near as much heat since the motor is no longer running at low rpms for anywhere near as long. And those nylon gears inside the motor are writing you a nice thank-you card.

Or…

Rather than using the throttle, you could also just start pedaling. I have set the KT controller to engage PAS as quickly as possible. Combine that with the BBSHD’s controller being told to hang back for the initial startup, and you have a completely thumbs-off solution that implements at a nice gentle pace.

So… It just works.

Or you can force it! Remember with this setup you have two throttles. There’s no law that says if you need it, you can’t jump the gun and either hit the rear throttle early, or hit it so the motor engages harder than it would have in your designated PAS mode. So if you need a little extra push thanks to an XL load of groceries, or a steep hill, you have options at your disposal.

Downshift? Schmownshift!

One of the mantras associated with smart mid drive riding is that you always Always ALWAYS freaking downshift the bike when you come to a stop. The LAST thing you want is to lug the motor up from a dead stop because of all the brutality it visits on your chain, your cogs blah blah blah. So that means you remember to downshift one or two… maybe even three times before you come to a stop. When the light turns green you upshift in sequence one gear at a time as you get back up to speed again. Thus as we all understand: you row thru the gears.

Another rule mid drive mavens repeat ad nauseum is – if you have an 11T small rear cog… stay the hell off of it. Its too small to use on a mid drive. It bogs the bejesus out of the motor from a stop, its too small to be able to get up to speed before the sun sets and if thats not bad enough, the teeny cog on even the steel Shimano clusters is alloy and it is not attached like all the others are. Its an individual. So not only do they dig into the cassette body harder, they die fast. Like Really Fast. As in a few hundred miles tops.

Well, on AWD mid drives like 2Fat, you can forget about all that. Because of the powered front hub doing its part (either thru a quick dab of throttle or just letting PAS start the bike), there is no longer a need to shift at a light. You can forget about the whole process. Just leave it and it’ll be fine as if it was a hub motor! In fact the front motor allows the bike to increase its speed so it gets up and goes fast just like a hub motor does.

I found this out within a day of building the bike, and since then learned from experience the 11T cog will last about 1500 miles before it typically cracks (two so far). Thats not so bad for a readily available US$7 part. And if I wanted it to live longer, well it wouldn’t kill me to go up a gear at a light once in a while.

At the office, outside my e-garage. There is a trail network along my commute route that 2Fat lets me take

Wrapping It All Up

2Fat itself is not the ideal example of how to execute this concept. It is a product of when it was built and my knowledge level at that time. In the present day, I for sure would not want to build a bike with two batteries, and if I did I would NEVER put one on the back rack. But thats partly the limits of the frame I used. I came within a hair of using a Salsa Blackborow frame kit for this bike until, at the last minute, this titanium beauty fell into my lap for a song… but thats another story.

Next, I wouldn’t use Shimano components thanks to the real estate problems introduced by the shifter. Instead I’d use SRAM components so I could do one throttle per thumb.

Really the Great Pumpkin with its XL size and XL triangle, plus its SRAM shifters – would be ideal here. But them’s the breaks. This is what I’ve got. Boo hoo.

With that said… I did learn as I went along, and in 2021 I returned to dual motor bikes with the Lizzard King, a bike meant to prove a different kind of AWD could be awesome: You don’t need the 80Nm, 35a punch of the Pumpkin’s or 2Fat’s front hub to gain the benefits of AWD. A low power implementation, done a little differently, should be very effective and appeal to a much broader range of everyday, low-speed, low-drama ebike use. And…

SPOILER ALERT: It worked unbelievably well.

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