Category: Dual Motor AWD

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

The Easy Way Or The Hard Way?

Lets make things as difficult as possible and do both. My loss is your gain and now you can see the results of both paths. I don’t regret this one bit (at least, thats my story). It gave me a spare wheel and motor, which is a good thing for a bike I need to depend on. I’ll lay out both paths and you decide how you want to do yours.

The Easy Way: Just Buy a Kit

In my run-up to buying my Bullitt frame kit, I looked extensively for the right 48v motor with a 20″ wind. It turns out those are pretty uncommon. Usually they are 36v, with a 250w or at best 350w rating. Oftentimes the winding is questionable as being suited for a 20″ wheel. Usually a motor is wound for larger 26″ or 700C wheels, and the torque is just not there for a little 20″ wheel build. Perusing EBay and AliExpress listings, you are often left wondering if what you are seeing REALLY is the variation you are looking for.

I lucked out, and found posts on the Bullitt: The Dark Side Facebook group from someone who had just finished receiving and installing a complete 48v, 500W Bafang front motor kit. Based on what the posts showed, it was quality stuff. So I bought one myself: A Greenergy 48v, 500W complete front wheel kit. This kit was advertised as express-shipping from China to the USA and that is really what they did. I had it in a few days and followed its progress all the way here via the Fedex tracking number I received in my Ali control panel.

It was helpful to already have experience with Bafang geared hub motors, to understand their reliability and performance. It also helped that I knew exactly what other hardware worked with them. Particularly the display and controller I eventually wanted to use on my custom build vs. this kit.

A word on buying from AliExpress:  Its kind of an adventure.  Definitely not as convenient as buying from the USA, but if you have experience doing it, you can smell out the bad actors.  I have bought many ebike parts there - this was not my first motor shipped direct from China - and have only had a few sub-optimal experiences with low-risk, low-cost parts.  Don't fear the platform.  Its a professional operation.  But if you are going there for the first time try and buy from a source that has been recommended to you directly.  Let some other pioneer take the arrows in the back.

Up front: I knew I did not want to use the ancillary parts (controller, throttle etc.) that came with the kit. For the low price they were charging, I considered those parts throwaways and was only interested in the right configuration of motor already built inside of a decent if not especially noteworthy wheel.

Waiting in the wings:
It is present day, and the Greenergy kit wheel has a new Schwalbe Big Ben 20×2.15 belted tire mounted on it. Inside is a Schwalbe A7 tube with Flatout sealant inside. Recently I swapped out my regular wheel, described below, so I could take my time re-greasing that second motor at its current 1000 miles. The G020 motor is adequately greased from the Bafang factory, but only barely so with white lithium grease that needs refreshing every 2000 miles at best. Since the above motor/wheel was an extra I was able to pull it apart, look inside, clean it out and re-grease it with Mobil28. That grease will at the very least have triple the service life before another re-grease is in order.

Is it the best grease for the job? Opinions vary widely. Mobil28 is a favorite in the DIY community and I can say from having it in geared hubs over a couple of years it has never done any harm. The motors I have used it on have never behaved differently other than to run a bit more quietly.

The Hard Way: A Custom Wheel Build

I knew from my previous AWD builds what controller I wanted to use, and I already had all the small parts like PAS sensor and throttle. The only thing needed was a display and I had an easy source for that.

In the end, the electronics were easy. It was the mechanical bits that were tough. I had a hell of a time getting hold of the right spokes, nipples and rim. Once acquired, I had to wait about 6 weeks for my poor, perpetually-backlogged wheel builder to get to making the thing. Having the kit wheel I could just plug in was great. I was able to ride the bike maybe two months earlier than I would have otherwise.

Having just finished buying one Bafang G020 with 11T winding, I didn’t need to expend any more energy figuring out what motor to use. I just needed to find a bare one. I was able to acquire one from the same guys who sold me the kit – for just over $200 on AliExpress (and it took quite a while to arrive this time). Thats the good news. The bad news is I can’t give a link to that motor as its no longer available there. But I can display a picture of the almost-identical motor model designation, and show you what you want to see for a comparable buy for a 20″ wind:

Reading the Bafang factory codes in the image above:

FM	“Front Motor”
G020	Model number
500	Rated for 500 watts
D	Disk brake compatible
12	“12T”, or 12 turns of copper winding on the motor core

My motor is 11T, not 12T. 12T could work on a 20″ wheel, as it gives you higher torque and consequently a lower top speed than 11T. However my 11T motor works perfectly as I want it to – right in the Goldilocks zone for a front motor that I don’t want to be too powerful off the line (no need to pull hard on that front fork – or the fork’s dropouts) and which starts to peter out just as the rear mid-drive starts kicking in hard, for a nice drama-free balance. A 12T motor would have a lower top speed that might make it die off below the typical cruising speed for this bike and I’d rather keep both motors working for as much of the range of normal use as possible.

Here is a link to what appears to be a very similar if not identical motor for sale on Amazon. You will want to ask the seller what the motor winding number is. Based on the similar name of the seller on the listing as of today, this may be the same one I bought mine from.

Rim Choice

For a rim, I wanted a wide BMX rim to better accommodate the plus-sized, 2.4″ Schwalbe Super Moto X (belted) tire I wanted to use. 2.4″ is outside the envelope of most Bullitt builds, but it will fit the fork easily and the frame barely. A tire that wide needs a wide rim. I chose the Alienation Black Sheep. It was the widest double-wall rim I could find. Its spoke drilling is angled, which should help when fitting short spokes into a small rim with a great big hub in the middle.

Spoke Choice

I specified Sapim Leader spokes in 12 gauge, with brass nipples. Once again I used Stoic Wheels as my go-to source for custom cut spokes in a world where you can pretty much forget about finding such things. He’s come thru for me on I think three separate builds now.

The spokes were my call. The wheel has proven (so far) able to take anything I can throw at it without any issues. But if I had it to do over again, I would not have chosen such heavy spokes for such a small wheel. They’re strong and all, but a spoke this heavy-duty did not like to be worked into a wheel this small with a hub this big. Sapim spokes are high quality and most likely the 2.3mm/13ga would have been a better choice, or maybe a Sapim E-Strong 2.6-2.3mm single-butted?

For me this is water under the bridge, but for anyone wishing to do a similar wheel build, consider carefully. My trusty longtime wheel builder at Stevens Bicycles got it done, but he said it was the most difficult wheel he has ever built. Looking at the spokes in the wheel, you can see why it was a struggle. Wheels generally derive their strength thru the rim, and the spokes need to provide some flexibility. If the spokes are too strong, there can be negative consequences. I clearly don’t have flexibility (think shock absorption) in this wheel … so fingers crossed it doesn’t come back to bite me.

Torque Arms (plural)

The G020 is rated for 45 Nm in its 350w, 26″incarnation. At best it is good for 60 Nm here in a 20″, 52v system with a 25a controller (thats set to slow start no less!). So, not exactly a powerhouse by design. You may not even need a torque arm on the Bullitt’s chromoly dropouts. But in my past I have ruined one chromoly fork and seen countless others destroyed by front hub motors. I consider a properly made torque arm essential as cheap insurance. Look at the pictures of the front wheel seen on this page and you will note that I have two of them. More is always better.

The Grin V2 arms I am using here are super easy to install and just as easy to remove if you have to pull the wheel off – just unscrew the socket cap at the dropout and the torque arm becomes a glorified washer.

PAS Sensor Installation

This was a major bit of fiddling that I have fortunately done before, so I didn’t have to do any heavy lifting to figure out how to make it happen. The job is to set up a pedal assist disc sensor on the bike, except the BBSHD is located on the drive side where the sensor goes. There’s no way to use it on that side, period end of story.

There are a couple of alternative sensors available that are meant to be usable on the non-drive side. Why is that a thing? The problem is anything meant to work on the drive side, which is moved to the non-drive side, is going to be reading rotational signals backwards, so it won’t work. Thus the left-side, or ambidextrous alternative. However this ambidextrous sensor is noisy and can fail via crud ingestion.

Using my chosen KT controller, its also possible to use one of two ‘reverse direction’ settings, so you can use a standard sensor. This was an option, but not necessary because, fortunately, I used a little trick that kills two birds with one stone: This particular sensor is held in with a screw rather than being molded in place, so I was able to simply reverse it in the mounting ring.

This not only solves the sensor-backwards problem, it also means the mounting ring is pointing in the opposite direction from normal, and now holds the sensor further out rather than tucking it in closer to the frame. That just so happens to be exactly what I want when mounting it in conjunction with BBSHD bottom bracket locking rings. You can see that in the pictures below.

What you see above on the right is an early test fit that is not complete. On the left you see the full, final setup. To anchor down the motor and then the PAS sensor ring, I used an inner ring, capped by the commonly-used dark black outer trim ring for the motor. Then came the sensor, capped by another inner motor mount ring. That third ring sandwiches the sensor mounting ring and holds it into place. My usual BBSHD installation uses two inner rings tightened together, jam nut style, but with the extra axle length sticking out of the 68mm bottom bracket, a traditional inner6+outer, followed by another inner did the trick. Stacking them like that has the added benefit of ensuring the motor never moves. The PAS sensor mounting ring is sandwiched as if it was a big washer.

Another reason the ambidextrous sensors don’t work well is they eat up about 1/2″ of real estate on the axle. As you can see on the left photo where the crankarm is torqued down fully… there ain’t no room for that here. There is however enough room to put on the standard magnet ring, and if you look closely you can see I placed a rubber o-ring on each side that in turn holds the magnet ring tightly in position, just a hair away from the sensor pickup.

Net result: Pedal assist is reliably enabled on both motors. That is a thing of beauty when you can get it to work.

Controller – Choice / Settings / Location / Wire Routing

All of my hub motors have been Bafang geared hubs, and all used KT controllers and displays. So I went with what I was familiar with. As noted above, sticking to what I know let me immediately solve the PAS sensor problem, among other things. I also already knew what I needed in terms of motor configuration within the controller so it operates safely within the confines of how I wanted AWD to operate: Seamlessly and without drama on a bike subject to extreme loads. I didn’t want this motor to be pulling hard on a bike with a potential total system weight in excess of 400 pounds.

So I knew I needed a KT controller. I also knew the 35 amp models I have used in the past were a) too strong and b) would not have the right motor plug. 35a controllers use the 3-pin Julet Z916, which matches up to the higher powered Bafang hub motors. A 500w motor has the ‘small’ HiGo Z910 9-pin plug, and KT controllers with that plug are in the 15, 20 and 25a range. I opted for 25a as I’d rather dial down too much power than to need more and not be able to get it.

However, I didn’t need to do much of anything except set the controller to max amps and slow-start (the C5 setting).

As to controller location, once again as with my previous AWD bikes I used a handlebar bag and simply set the controller inside of it, with the open top of the bag providing ventilation. This time I didn’t bother to use grommets to create reinforced holes in strategic spots in the bag. Because of the different sort of layout the Bullitt provides to the builder, I was able to simply run up a single bundled, loomed cable up and into the open top of the bag. You can see that cable in the right side cockpit photo below.

Controller settings are as follows for the G020 motor on a KT controller:

The P settings are mostly specific to the motor hardware and not to be fiddled with, although I have P5 set to operate on ‘real time voltage’ rather than let the display try and calculate it via a half-baked method built into the controller. “Real time voltage” is just as useless, actually. Free advice: Use the LCD3’s live numeric voltage readout and ignore the graphic.

Beyond that, I will leave the settings to you to figure out (its not hard, and bear in mind I was deliberately toning down the performance of the motor, looking for smooth and drama-free AWD performance), with the following manual link:

For a complete KT-LCD3 manual translated by a native English speaker, follow this Google link for the Dillenger KT-LCD3 manual.

Display and Remaining Electrical Bits

The throttle on this bike is your basic thumb throttle. I intentionally used an old design of KT controller so I could re-use PAS sensors and throttles I had sitting on my parts pile for years. Modern KT controllers use master wiring harnesses very similar to the bundled BBSHD one-to-many wiring harnesses, and so if you are purchasing one in the present day your throttle and brake cutout connections will match to that harness.

The display I used is a simple, straightforward, old-school KT model LCD3. The LCD3 is an inexpensive old standby that does everything you could want a display to do, without the fancy bells and whistles of the current generation of color displays.

But… I would have rather had a ‘pretty’ one. The KT-LCD8H is effectively the LCD3 with a redesigned color display and layout. More usefully, its settings are all visible on a single screen and can all be edited from that one screen. The LCD3 makes you work for it the old fashioned way: One setting at a time, one screen at a time. Miss one and you have to cycle thru all 30 of them after a reset. Its not the end of the world but you only have to use the LCD8H’s settings screen once to appreciate the convenience.

Still, the LCD3 does its job and is economical. Thanks to the wonkiness of the global supply chain, the Model LCD8H was unavailable when I was in the market to get the display I needed for the Bullitt.

Motor Cable Routing

Last and … well, probably rightfully least is the routing on the motor cable from the motor itself back to the controller that is hanging all the way back in another county, back under the handlebars.

First of all, a connection extension to the motor cable is necessary. I bought this one from Amazon – a 60 cm extension. Between the relatively long length of cable coming from the controller, and the length from the motor, this was a perfect size. However, cable lengths vary widely from one batch of controllers or motors to the next, so have your own in hand before you decide on your needed extension length.

Many builders run the motor cable up the fork and then back down again, then running it underneath the cargo box. I wanted the cable protected from ground strikes and weather, so I ran it inside the cargo box as I did the front brake cable (more on that in the separate Bits & Pieces installment).

So not only did I run it thru the cargo box interior, I found the steering arm provided me with a shorter highway straight to that cargo box ingress point. Sure, its not a fixed mount but neither is the fork blade, which also needs slack so the fork can wiggle back and forth as you dodge potholes, run around in circles etc.

Again wanting the cable to be protected, I re-used some unused bits of 3/4″ tubing left over from what I did inside the cargo box. A couple of 45-degree elbows, a few centimeters of straight tubing and a few zip ties later, a cable tunnel was firmly attached to the top of the steering arm. The motor connection from motor to extension is housed inside this tube, and experience has shown the downward angle of the front-most elbow is enough to keep water out of the tube. Speaking of which this tubing also keeps water and crud from taking its best shot at the motor connection.

There is enough slack on both sides of this tubing, along with smooth, rounded edges, to ensure there are no motor cable pinches and no tight bends that will break down the cable over time.

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And that, as they say, is that. We’ve pretty much covered everything of interest on the front motor wheel build, installation and configuration. You can use this to inform your own front wheel ebike build

Or take it as a guide on what not to do, as you please.

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Thats it for the front motor and wheel. Lets talk about

The BBSHD Rear Motor and Drivetrain

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

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.

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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.

UPDATE: An Alternate Path

In 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.

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.

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.

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.

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Thats it for the brakes. Lets talk about

The Front Motor and Wheel

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

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.

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.

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.

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 Hours	32
Output Cable	XT90S / 8ga
Charge Cable	XT60 / 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.

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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 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.

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.

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.

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.

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Which leads us straight into the next episode:

The Battery (and Battery Box)