Mongoose – Chapter 2 (Brakes)

“My brakes are too effective” 
— said Nobody, ever

I am a firm believer in Big Brakes.  I learned when building a hot rod track car that everybody pours money into motor and suspension, but brake upgrades often come as an afterthought (usually accompanied by soiled underpants).

As a daily bike commuter, I also want trouble-free operation.  And since what I usually ride is a big, fast, heavy ebike, I appreciate big brakes a whole lot more since I am riding a rolling worst-case scenario.

Now, the Mongoose Envoy donor bike is the subject of this series, and it is not a fast bike.  It hauls lots of stuff though and thats probably worse than merely shucking speed.  So far, I have loaded it with about 140 lbs of groceries in addition to my own 250 lb self.  Add to that the bike’s roughly 50 lb weight.  With all that, the brakes that come with this bike from the factory really have their work cut out for them.

I suppose those factory brakes are OK… If I set aside how spoiled I am with my usual upgrades.  I can see they are about average for a low-cost bicycle.  While I wanted to keep this bike’s cost down, a couple things pushed me to upgrade.

First, out of the box the front brake essentially did not work at all.  It seems it was so poorly adjusted that all it did was caress the front rotor and do nothing to help stop the bike.  This was after I adjusted the inner and outer pad positions (the stock brakes have a dial for each side) as well as the caliper on its mount.

The rear brake … well, it did apply what I would consider to be moderate pressure.  A bit light but in the ballpark of what you’d expect from a cabled system.  But there is a long cable run to the back of that long frame.  A fair bit of my brake lever travel was eaten up by flex in the brake line, between lever and caliper.  An inspection of the brake housings showed they were not lined/compressionless – not a shock given the bike’s price point, but bad news for braking.

My initial solution was a game I have played before, and I should have known better… but I wanted this bike to be low-cost, so I tried a half measure:  I upgraded the calipers to Avid BB7’s (I had a spare set in my garage), which have a very good reputation.  But no matter what they are still cabled brakes.  I ended up wasting half a day trying to get them just right and never did.

The front brake came together quickly.  It didn’t want to stay in adjustment but thats what you get with cables.  Its stopping power was just fine.  It was the rear brake that was a waste of time.  I tried every trick in the book to get it to be effective – perfect was never an available option.  Most of the blame goes to the aforementioned flexy cable housings.

And mounting them?  Avid calipers use a semi-hemispherical washer set above and below the caliper to allow it to be angled if need be, and that makes its positioning options quite fluid.  The height was never correct and there was always some kind of rubbing somewhere.  Regardless of how I shimmed or re-jiggered it, something was not right somewhere.  I like to think of myself as something of a brake whisperer – if a brake set can be finessed, I can get the wheel spinning perfectly without so much as a touch from a misaligned pad or rotor.  Not this time.

So I said to hell with it and went back to my old standby.  Magura MT5 hydraulic brakes.  This makes my 5th set across my 2-wheeled fleet so I am pretty familiar with them.  Why these brakes?

  1. They are powerful.  4-pistons in the caliper means four clamping points onto the rotor.  Its like the difference between grabbing something with one hand versus using both.
  2. They are smooth to activate.  Unlike cabled brakes, you can use one or two fingers to gently tug on hydraulic brake levers.  For the Maguras, they have lots of travel so it is easy to modulate the force applied.  Despite their power they are very gentle unless asked to be otherwise.
  3. They are dirt-simple to install.  Use a Magura adapter to match your rotor size and bolt the caliper directly to it.  Done.  The use of Magura adapters coupled to their caliper results in a perfect height every time.  No shimming.  No dinking around with axes and semi-hemispherical washers… just bolt it on, eyeball it to center and tighten down.
  4. They self-adjust.  Yup thats right.  You centered the caliper at installation.  The pads align themselves.  Really.  You won’t mess with them again until you wear the pads out.

Ordinarily you pair these brakes with a Magura Storm HC rotor.  These rotors are 2.0mm thick, which is thicker than the typical 1.80mm thickness most rotors(including the stockers on the Mongoose) come in at.  In addition to having more meat on them to do their job (a rotor is a heat sink and more metal = more heat sink) thicker rotors are less inclined to warp.  In fact I’ve never seen one do that across any of my bikes and thousands of miles.

20170415_112904.jpg
This is a fresh Magura Storm HC 203mm rotor just after installation on an ebike.  Notice the heat discoloration from the brake bedding that was just performed.  Also note the caliper is bolted straight onto a Magura brand adapter with no need for shims.  Matching the brand on caliper, adapter and rotor makes for perfect alignment.

With all of that said, I have found a better rotor than the Storm HC – the Tektro Type 17.  Its designed for downhill bikes, who need to stop under the most extreme of circumstances.  These rotors are 2.3mm thick and as such are even more substantial – and even less likely to warp.  They fit perfectly on a Magura braking system, with the tops of the rotor ‘waves’ matching the top of the pads, and only a hair of lower rotor surface being untouched… not because the calipers are misaligned… there’s just more rotor face than you can use.

Here is one of these monsters, installed.  Note the marks left by the pads on the surface, and its noticeable thickness.

IMG_20190622_113631.jpg
The Tektro Type 17 mated to a Magura MT5 caliper.  Once again note this caliper is bolted straight down onto its adapter and fitment to the rotor is essentially perfect.

Its worth noting both the Magura and Tektro rotors discussed here are generally too thick to use with normal brake calipers.  Not so with the MT5’s.  And if you are guessing the extra-thick, never-warping rotors are going to last longer, you’d be guessing right.  the rotor above on the orange bike… so far I can’t seem to wear it out.  That bike is my daily driver and I can’t measure any wear after about a year installed.  I have worn out a set of the Maguras, but it took thousands of commuting miles.

Thats nice.  How Much?

So all this is wonderful.  What did I spend?

I’ll give you a couple different answers on that.  On every bike of mine but the Mongoose, I used the Magura MT5e brakes, which include a safety cutoff that wires into the BBSHD via the brake lever.

Here’s what an MT5 versus an MT5e lever looks like:

Note: the comparison above is deceptive as the MT5e lever appears the same size as the MT5 on the left.  It ain’t.  The ‘e’ lever is actually a fair bit larger.

Thats the only difference between the two brake sets, but its kind of a big one.  First of all, the MT5 lever on the left is often cited as feeling cheap or unsubstantial.  I do not find it so, but I understand where the sentiment comes from.  Most riders who use these do so on singletrack MTB’s where there is a lot of banging around, over and up against things.  On a street bike this need for durability – and bend-ability – is not so much a factor.

The lever on the right has the obvious connection that leads to your motor, so that when you depress the lever, your motor power cuts off for safety.  This lever is also constructed completely differently.  Its larger, made of alloy and its shape is much more… substantial.  Also note the metal pin in the middle of the lever itself.  This is a hinge.  It allows you to gently touch the lever and activate the cutoff while not activating the brakes.  This can be handy if you are using the brakes as a sort of clutch to cut the motor out during shifting (the reasons for doing this are discussed here).  This second hinge also gives you a surgeon’s precision when modulating brake pressure.

Currently as I write this in October of 2019, the cheapest source for MT5 and MT5e brakesets is here.  This is where I bought the MT5 brakes I have on the Mongoose.  I have also bought MT5e sets here in the past.  Note that while this is a web site in Germany, and you will have to pay shipping charges, they are reasonable and the prices are so low you still save money.  Especially if you get a few sets of extra brake pads, which are roughly 1/3 of what you will pay for the same name brand pads in the USA.

If you are using the MT5e levers with the cutoffs, then you also need an adapter to mate their red HIGO/Julet plug to the yellow one on the Bafang motor used in this project.  Those are found here.

Brakes (two options)

  • If you are just going the lowest cost, max-functionality route like I did, you’ll pay about $150 for a complete set of brakes (MT5 only).
  • If you instead go with MT5e’s (you must select the version that is “Normally Open” a.k.a. “Closer”) you are looking at around $100 per axle at the above German web site.  $125 if you buy from a USA dealer (I like Planet Cyclery on EBay – they are a Magura dealer and performed a free warranty replacement for me a year after a sale).  Add to that about another $30 for the cutoff adapters.  So about $280 total.

Brake Caliper Adapters

Adapters for the rotors are going to run you $7 to $10 each.  I used 203mm rotors front and rear so a Magura QM9 / ISH-203 in the rear and a QM5 / ISF-203 in the front.  Buy these with your brakes and pads and save the shipping cost.

Rotors (two options)

I am only listing two options here in case you cannot get hold of the Tektro Type 17 rotors.  Make sure they are specifically the Type 17 as Tektro makes other rotors that look almost exactly alike and are very common on the marketplace, while the 17’s are relatively rare.

  • Magura Storm HC rotors are meant to work with these calipers and do so just fine.  They are available for about $21 at the same source as above, and at many other retailers for only a little more.  The only reason I don’t use them anymore is I found something better…
  • Tektro Type 17 rotors are only regularly available from two sellers I am aware of, although I am certain there are more out there.  The first is from seller hi-powercycles and is where I buy all of mine.  The second source is at Empowered Cycles.  Empowered also sells the Type 17 in a 180mm size, so if for some reason you decide you need a smaller size, they can sell you one.

Replacement Pads

You have two choices, but if you are smart, there’s only one you should pick

  1. MT5 pads (Magura Type 9) – These 2-piece pads provide a single surface for the two caliper pistons to press into.  They do provide excellent response, but the type 8’s are … more better.  Plus in order to remove Type 9 pads, they have to come out the bottom of the caliper.  You have to remove the caliper from the mount to make that happen.  More work for you.  Unless for some reason you decide you want to use the Type 9.C Comfort pads (hint: you don’t) there is no reason to use Type 9 pads past using up the set that comes with the new calipers.
  2. MT7 Pads (Magura type 8) – These 4-piece pads are better in every way than the Type 9.  Most obviously, they can be removed from the brake caliper from the top, so you just undo the screw-in retaining bolt, pull the pad out with your fingertips and slide in a new pad (they set nice and easy thanks to ingenious magnets inside the caliper).  Not so obvious:  the independent Type 8.P pads have been measured to add a significant increase in clamping torque to the rotor.  They also come in a Type 8.R pad, which has a sintered pad compound.

Whats the Down Side?

Just one:  You will have to learn how to cut and bleed brake lines.  Honestly… its easy to do.  But you will have to do it.  Check out the videos at the bottom of this post.  They are what I used to figure it out.  You will need a bleed kit to get the job done.

HOWEVER…

You can cheat.  Each brake set comes with 2200mm of cable, pre-bled and fully operational.  Just use it.  Run the cable, then loop the excess and stuff it into a handlebar bag.  There’s a little for the rear and a lot for the front.  I added a front rack and the little bag I have on top is where my extra cable went.  Its kind of disgusting how well it works and how its so low key I could get away with just leaving it like this forever.  But it is definitely a lazy kludge.  I’ll do the job right some weekend or evening this winter.

Performance

ummmm.  Awesome!  Duh…

  • They are not grabby.
  • You never have to squeeze hard.
  • They don’t fade.
  • There is always more brake available than you need.
  • They are silent (the sound of Magura pads on a rotor is sometimes referred to as “blowing bubbles” and this is actually accurate.  I’ll leave it to you to experience what that actually means for yourself.
  • The pads never need adjustment.
  • If you use the MT7 pads, you replace the pads without removing the caliper from the bike (and you also get a lot more clamping force as a bonus).  But since the MT5 pads come with the calipers for free, use them up.
  • The lines do not leak.  I have heard of hydraulic brake systems that leak fluid and Maguras … don’t.
  • These brakes use mineral oil rather than DOT hydraulic fluid… thats a big deal because DOT fluid is nasty stuff… corrosive to paint just for starters.  Mineral oil, on the other hand, is harmless.

Mongoose – Chapter 7 (Build Sheet)

I’ll try and keep this as simple as I can and simply list parts in what passes for a table in basic WordPress which does not support tables.  Over time as this project is filled out the reasons why I chose what I did will be covered in the various articles

Mongoose Envoy Bike               Amazon              749.99
Ursus Jumbo Superduty kickstand   Amazon               79.99
Jones H-Bar SG Loop Handlebars    Jones Bikes          79.00
Jones 205mm Kraton Soft Grips     Jones Bikes          20.00
Magura MT5 disk brake set         bike-discount.de    137.00
Thudbuster LT 27.2 XL             Amazon              119.99
ISH-203 203mm rear disk adapter   bike-discount.de      6.86
QM5 203mm front disk adapter      bike-discount.de      6.86
Tektro 203-17 downhill rotors (2) ebay (hi-powercyles) 42.40
Continental Contact Plus City     Amazon               69.54
   26x2.20 tires (2)
Sunlite thornproof 26x2.35-2.50   Amazon               33.90
   Presta valved inner tubes (2)
BBSHD motor kit                   Luna Cycle          699.95
   68-73mm standard motor
   Mounting hardware
   wiring harness
   speed sensor
   basic crankarms
   Luna 500C mini color display
   Universal thumb throttle
Second Bafang inner lock ring     Luna Cycle            5.95
Battery Solution
   Wolf V2 52v 12ah battery pack  Luna Cycle          549.95
   Potted, QD mount, 50a BMS and 
   Samsung 30Q cells
    -OR-
   52v 12.5ah battery pack, basic Bicycle Motorworks  369.99
   pack construction, 50a BMS and
   Samsung 25R cells
Luna Eclipse chainring            Luna Cycle           99.95
   Anodized black face                  
   Anodized gunmetal chainring
Lekkie Buzz Bars (crankarms)      California-ebike     99.00
SRAM EX1 144Lnk mid-drive chain   Amazon               28.99
 -OR-
KMC X9.93 (7 feet - more links)   Luna Cycle           57.75
Shimano HG400-9 12-36T cluster    JensonUSA            25.99
 -OR-
Shimano HG400-9 11-34T cluster    Amazon               24.60
Shimano RD-M591 9spd derailleur   Amazon               40.16
MicroSHIFT TS70-9 shifter         Amazon               23.99
ROCK BROS Wide Platform Pedals    Amazon               21.99
Raised rear deck
   Moose Skateboard Deck          Amazon               28.95
   aluminum unthreaded spacer     McMaster-Carr        10.88
      13mm OD, 25mm long, for 
      M5 screw (qty 8)
   countersunk M5 wshrs (qty 10)  McMaster-Carr         4.84
   stainless hex/flat head screw, McMaster-Carr         9.35
      M5x55mm (qty 25)
Front Rack
   Axiom Streamliner Front Rack   Amazon               47.99
   Delta AxelRodz skewers         Amazon               13.60
Wheel Build
   Sun Ringle MTX39 26", 30mm     Amazon              126.00
   Internal, 39mm external width 
   32H downhill rims (qty 2)
   DT Swiss 350 Classic Hybrid    Amazon              249.00
   rear hub, 148mm Boost, 32H 
   QR end caps for DT hub         Local Bike Shop      35.00
   Shimano HB-M475L front hub     Amazon               37.43
   DT Swiss Alpine spokes         Local Bike Shop     250.00



Mongoose – Chapter 4 (Motor Choice)

I have chosen a mid-drive as the best tool for the job on this bike.  It will not only be hauling cargo, it has to be able to do it in a steep hilly area.  If I was building for flat ground, a maintenance-free direct drive hub around 1.5-2kw would be the answer.

I’m not doing that though.  So mid-drive it is.  Now, which one?  there are plenty on the market and I have owned and in some cases still own several different ones.

Originally when I was planning this article, I was going to describe all of the major players in the market, and why I chose the one I did.  Instead I’ll limit my scope to the top two choices to better stick to the subject.

Second Choice: Bafang BBS02

This should be the first choice for most people.

I do want to say that as far as I know, as Bafang’s largest USA dealer, only Luna Cycle sells a BBS02 I would want to buy.  Luna uses their buying power to spec more robust controller internals that keep the BBS02 from frying its controller under sustained load … that was something of a known drawback of these motors in their heyday.  Also, Luna’s pricing strategy means their BBS02 kits are among the cheapest, if not *the* cheapest, BBS02 on the USA market.

Bafang mid drive motor kits are at the bottom of the the difficulty curve in terms of installation.  With one of these, you can have a bike up and running in an afternoon.  You’ll find a zillion Youtube videos and blog entries telling you what to do and how to do it, as well a multitude of experienced users in online communities ready to help you through whatever specific, quirky question you may have.

bbs02

Sidebar:  Bafang is a mainland Chinese motor manufacturer that is essentially the 800 lb gorilla of ebike motor manufacturers.  If you think companies like Bosch are market leaders, their volume is a fraction of Bafang thanks to their massive installed base in the Far East.  Bafang motors, while not perfect, are typically overbuilt, rugged, dependable and not very exciting.  Workhorses.  Chinese products have a reputation for ‘optimistic’ spec sheets and shaky quality.  Bafang is pretty much the opposite of that.  They underreport their motors’ capability – It seems one reason for that strategy could be so they can sell the same motor with different power ratings, with a higher price point for the ‘bigger’ one.  Again they are not perfect by any stretch, but for the beginner, working with a USA dealer of their products (do NOT be tempted to buy cheaper from an overseas vendor), its hard to go wrong.

The ’02 has been around for awhile, and what is sold as the ‘BBS02’ in the USA amounts to Bafang’s first effort at a kit offering (you can still buy BBS01’s – mostly overseas – and they are essentially a low-power BBS02).  It has long since been eclipsed in terms of power, and its aftermarket support for upgrades is not what you find for its successor, the BBSHD, but still the ’02 remains a rock solid product (IF you heed the caveats above).

A 750w or 1000w ’02 would have been my motor of choice for this project, except I already own two other BBSHDs.  As such I decided to keep one set of common parts across the fleet, so to speak.  I went with the more powerful next generation: the BBSHD.  More on that below.

Another Sidebar:  If you see these motors with the label ‘8FUN’, thats Bafang’s house label.  Usually those motors were manufactured for sale overseas in the Far East.  You can also find BBS02’s and BBSHDs with private labels on them.  Thats common.  Bafang will sell a private-labeled motor to anyone who will give them a big enough order.  Some vendors – like Luna Cycle, Bafang’s largest USA dealer – private-label and sell at a competitive price to builders.  Others just add their own label and crank up the price.

First Choice:  Bafang BBSHD

Bafang updated the BBS02 with the BBSHD (its called the BBS03 in some overseas markets).  The ‘HD is essentially more of everything you get in the ’02.  More robust.  More aftermarket support.  More power.  And more money.  But its still a bargain, with a bare motor running around US$450.  A complete kit providing you with everything you could ask for, plus programming upgrades (Bafang motors have a robust capability to customize their behavior, ranging from total power output to precise tailoring of each of the 9 pedal assist levels). should run you about $750 before you get to the battery.

bbshd

Myself, I paid less than that simply because I already have two other bikes that use this motor, and I have quite a few spare parts on hand.  I can just pick stuff up off the parts pile for zero added cost.

Stealth

You’d think this motor sitting in front of the bottom bracket like a giant wart would be obvious to people, but it turns out it isn’t.  Oftentimes, I get asked “Is that thing electric?” and when I point out the motor I see the questioner’s eyes light up in surprise.  So visibly it doesn’t stand out to people.  Especially since I keep the battery in a triangle bag – not to keep that part stealthy, but because that makes it easy to haul out and carry into the store with me.

The next component of stealth on an ebike is sound.  How loud is this motor?  To all intents and purposes, the motor is completely silent.  If you fire it up on the workbench, they definitely make an audible whirring electric-motor noise.  But on the road, even at the slowest speeds with no wind noise in your ears… you’ll be lucky to hear a slight hum.  And anyone next to you – like that poor sap you cruise by while he struggles up the hill in his analog bike – they won’t hear anything either.

Mongoose – Chapter 3 (Motor Types)

I am making a particular choice with regard to the motor I am putting on the bike that is the subject of this series.  I’m familiar with the various types – their strengths and weaknesses – but for the sake of the reader who may not be, I’m going to do a quick-and-dirty on each mainstream type.  If I’m not covering that motor type (looking at you, friction motors)  there’s a good reason that further research on your part will reveal.

There are three types of motors that make it into the mainstream of the ebike world

  1. direct drive hubs
  2. internally geared hubs
  3. mid drives

Direct Drive Hub Motors

mxus.jpg

DD hubs work with no moving parts and are effectively maintenance free.  The axle of the bike is also the axle of the motor itself, which is just a brushless DC motor with magnets running around the outer case of the motor (the rotor), copper windings wrapped around the interior stator etc.  Apply electricity and the stator repels (or attracts) the rotor, which results in the rotor spinning, and there is your powered motion.

Relative to the other motor types, DD motors produce much less torque.  That means there’s not much oomph behind the motor and you either help it along with a lot of muscle if you want acceleration, or you sit back and wait for it to spool up (in a worst case scenario you are hoping to get to the other side of the intersection before the light turns red again).

To get around that lack of torque, you use a really big motor and a really big, powerful battery.  Once you get into the 3kw-5kw and greater range, with a 60v or higher voltage battery, now you are talking about a bike that is accelerates acceptably (or insanely depending on how big you went) and can climb hills easily, even loaded with extra people and groceries.

The drawback to the above is that big motor, with its big metal magnets and large amounts of copper wiring is … big.  Heavy.  And so is the 2XL battery you needed to get big power out of that motor.

For a serious bike that can carry cargo, passengers etc. up a hill at speed, you are probably talking about a 125 lb bike, with a lot of that weight inside of the back wheel.  The battery is likely going to be on your rack as well (not your cargo) reducing your carry capacity.  At lower power levels (particularly those that are less illegal than the above noted 3-5kw) you aren’t looking at that kind of weight penalty.  But you get low performance as a result.  A direct drive motor that is not in the hi-power league will need a long run-up to get to cruising speed.  And if you want to climb a hill… well its the worst choice for that job of the motors you can choose from unless, again, you go big.

If you want to research the ins and outs of this type of motor further, you need to also look into ‘torque arms’, why they are needed with this kind of motor, and when.

Geared Hub Motors

Geared hub motors do a good job of providing more torque than DD hubs at similar power levels.  They do this by installing a planetary gear reduction inside the motor which connects the stator to the outer casing.  The motor spins nice and fast as it likes to.  The axle in turn spins the planetary gear.  This finally turns the outside casing and the wheel at a slower speed, so you and the bike can go down the road at a comfortable rate of acceleration.

img_20180704_054016
I opened this motor up for its semi-annual re-grease.  I also needed to deal with that rust you see.

Geared hubs tend to be lighter than their direct drive cousins, which helps with range and acceleration.  At sufficient power levels – lower ones than what a direct drive motor needs to do the same job – a geared hub gives some pretty good torque.  80 Nm in the case of the above pictured motor.  Mate that to a 35 amp controller and a commonly available, medium-voltage 48v battery and you have a really peppy ebike.

Whats the down side?  Those nylon gears will take a lot of abuse (really a lot), but they won’t last forever.  Especially if you subject the motor to regular extended hill climbs, or you are subjecting it to a lot of stress… like a full cargo load.  If you try to solve this problem with steel gears (Chinese Ali Express specials that may not have been the best re-engineering job) you find out why motor manufacturers use nylon:  noise… and metal shavings.

You will also have to open those motors up every few thousand miles and re-grease them, as the grease perishes over time.  Lastly, geared hubs really do not exist at the higher power levels (most I have seen are the MAC motors peaking at around 1500w with a special controller to get them up that high).  Any higher than that and the gears really can’t handle the power.  Unofficially, A Bafang G060 fat motor like in the picture above can handle a 60v battery and 35a controller that delivers 2.2 kw peaks … forever.  But I wouldn’t bet my motor’s life on it being able to do long term that under severe loads like cargo duty or living in steep hills.

Final thoughts on hub drives

Both geared and direct hub motors power your bicycle directly through your hub axle.  They are the hub in fact.  What this means is, your bicycle powertrain is entirely irrelevant to what the motor does.  The power to the ground is transmitted directly from your axle.  In fact, if you want to have some fun with your hub bike, you can remove the chain.  Then ride down the street with your pedal assist turned on, and pedal the bike.  It will work just great.  Of course you aren’t getting any exercise and likely you don’t want to ride like this, but it illustrates the fact that the traditional bicycle powertrain is not needed.

Your pedals and chain now exist almost solely to provide you, the rider, with exercise.  You put as much effort into pedaling as you want, and that can be just mild pressure or pushing hard the way you would riding an analog bike.   It is now the motor thru the axle that is doing the real transportation work.  This fact is not lost on ebike manufacturers, and this greatly reduced duty cycle means hub-based ebikes tend to have cranks, chainrings and rear clusters that would not survive long if given the hard life an old-school analog bicycle receives.

Geared hub motors need torque arms just like direct drive hub motors, albeit not so much at the lowest power levels (i.e. 250w and 350w).

Lastly, both types of hub drives have this significant benefit:  they don’t require any special knowledge or care to use.  You can jump on the bike as a complete newbie and start riding.  So long as you aren’t riding some kind of hot rod that is hard to control, you already know everything you need to ride happily down the road and not cause any issues.  That makes hub motors of one sort or another preferred for most casual riders who are not challenged by their terrain.  That isn’t true of your more powerful mid drives, but I’ll get to that below.

Mid Drive Motors

‘Mid drives’ are known as such because the motor sits at the middle of the bicycle.  Typically replacing the bottom bracket.  As much as hub drives dominate the lower-cost, DIY and upgrade ebike markets, mid drives dominate the big-name commercial-manufacture market.  In particular, and most telling as to the benefits of the mid drive, E-MTB’s are exclusively mid drives, and for good reason.

img_20190603_194127
Yes, this is an ebike (and yes, its mine).  Look closely at the chainring.  See the mid drive motor hiding behind it?  This motor peaks at around 440 watts of final output which in the USA is well under the legal limit.

Mid drives work on an entirely different principle than hub drives.  Hubs, as we noted above, power your bike thru the axle, and your drivetrain is just along for the ride.  In terms of assistance, the hub drive bike is a 1-speed, and this is part of the reason hub drives don’t do so well in hills or fast acceleration, unless you start getting into big power.

But a mid drive works just like you do:  It pours on the power thru the bicycle chain.  That means if you hit a hill, you can downshift into a lower gear, keep the chain spinning fast and get up the hill more easily.

Gee thats great.  And since much of the world has legal limitations to 250w of final drive power, you can’t really put enough power into the system to break anything.  An average person in good shape can put between 50 and 150 watts of power into their drivetrain during a ride.  Thats what an old-school analog bicycle drivetrain expects to put up with.  250w isn’t a whole lot more than that (a trained cyclist can pour on roughly 400w or so… and sprint briefly up to around 1500w… which is still not really enough to make a slice of toast).

About that 250w limit… First of all, here in the U.S. that number is typically “less than 750 watts” according to our national manufacturing/consumer safety standard.  Many of the individual U.S. states have vehicle codes that separately define what is an ebike vs. a moped vs. a motor vehicle.

Beyond that, in the last year or so we’ve started to see rebellion from major E-MTB manufacturers against the almost-a-joke 250w EU limits.  What we are seeing is the complete disappearance of any mention of wattage output.  Instead all you see references the Newton Meter (Nm = torque) output of the motor.  Unstated is the *ahem* potential for the motor putting out more than 250w.

Really, torque output is what matters in terms of figuring out how much assist you are getting, and mid drives just pour on the torque.  A Bafang BBSHD, the de facto volume-sales king of the American DIY market, puts out 160 Nm continuous torque when it is fully utilized.  That is about double the momentary peak of what the big geared hub pictured above is capable of (and that geared hub is among the biggest of its genre).  Direct drive hubs are in the 40-60Nm range unless you go all Mad Max on the power levels.

So … easy choice everyone needs a mid drive!  Well, not so fast.  With great power comes great responsibility repair bills if you don’t use your head.  That means build it right and learn how to ride it.

Remember the wattage output a normal human is capable of?  The level that a quality drivetrain is expected to be able to handle?  Well, the above referenced BBSHD in off-road mode, pouring out those 160 Nm, is feeding about 1500-1700 watts to the drivetrain.  Continuously.

You want to figure out how much wattage is going to your motor?  The formula is Volts * Amps = Watts.  So a 52v battery running at its nominal 52v rating, multiplied by a BBSHD running at 30 amps is… 52*30=1560 watts.  At a full charge that battery is 58.8v, so 58.8*30=1764 watts.  Continuous output.  Yes, really.

So, when we build a DIY mid drive bike, we first want to buy parts that are meant to take this kind of punishment.  They are out there on the market but frankly a lot of DIY builders, riders and even most ebike sellers are ignorant of this.  You want:

A good narrow/wide front chainring

Made of 7075 alloy most likely, but if you can get a steel ring, do it (Wolf Tooth is the only one I know of and they only come in 30T and 32T sizes).   This style of ring typically has wider, taller teeth that eliminate chain dropping issues.  In particular rings made specifically for mid drives are sold by Luna Cycle, who manufactures their own here in the USA, and Lekkie, a New Zealand company with a stellar reputation who sells thru ebike vendors everywhere.  The latter two names are focused primarily on the BBS02 and BBSHD markets although Luna does make rings that will work on other platforms.

An ebike-specific chain

The interwebs are filled with complainers crying about how their chain snapped.  When you ask how many of them re-used their $6 stock chain, or who just bought a ‘nicer’ bicycle chain, the numbers pretty much climb up around 100% of chain failures (chain alignment will be dealt with below).  E-bike specific chains in various widths for various speeds are sold by KMC (my favorite is the X9e/E9 9-speed) in 136 link lengths.  SRAM’s EX1 ebike group has its own 144 link chain.  Lastly there are the Connex chains by Wipperman.  The common factor in why people don’t use them (besides not knowing they exist) is price.  These are US$35+ chains (you can buy smart and get them for less if you know where to shop).  But… They.  Don’t.  Break.

Lastly, you can find a specialty vendor and buy a specific length of chain all in one piece, so you don’t have to section two chains together (if you do that, it creates a potential weakness at the joining point).  This is by far the most expensive option.   I bought a 7-foot length of 9-speed chain from Luna Cycle and it ran me about $60.  But my Mongoose Envoy, with the long-cage Deore derailleur I added, needed 152 links to be set up right (I keep a 144-link SRAM EX1 as a hot spare and it will work fine in a pinch).

kmc x9e.jpeg
The KMC X9E.  Those mushroomed pin ends will be torn off if you use a chainbreaker on them, so if at all possible just remove links to make it shorter, don’t add any to lengthen.  re-attach with master links.

A steel cassette cluster

You have two choices for this, generally.  First is the SRAM EX1 cluster that is an 8-speed, has a range of 11-40, is made of tool steel and meant to be used with the EX1 shifter which will only shift one gear at a time.  The rub is the cluster alone runs about US$385.  Its worth every penny (I have one on my E-MTB, so it had better be), but that cost is insane.  How about spending US$15-25 instead?  Just buy any cheap Shimano rear cluster.  In particular the HG-200, the HG-400 or the HG-50.  All in 8 or 9-speed.  They use steel, not alloy, cogs, and most importantly the entire cluster is welded together into a single unit so the punishment dealt to the cassette body is distributed across its entire width.  These Shimano clusters are an excellent example of something that is awful for an analog bicycle and highly preferred on an ebike, where durability is vastly more important than light weight.

Shimano-CS-HG400-9-9-speed-Cassette-silver-12-36.jpg
This is the 12-36T 9-speed cluster I am using for my Envoy build.  Don’t look for any bolt heads to allow disassembly.  Only the 12T cog is separate from the 1-piece body.

A steel cassette body

Here again, what sucks for a bicycle is great for an ebike.  A steel body will last.  An alloy one won’t.  Take a look below.  On the left is an alloy DT Swiss cassette body with about 1600 miles on it.  It comes from a DT350 hub, which is at or near the top of the line as bicycle component brands go.  The cassette cluster I used was a welded steel Shimano, so those notches you see still tore into it despite the gentler damage the welded cluster does.  I almost exclusively used the 11T small gear on this bike and on the far right you can see that section is torn into further than the rest (the last cog is free floating so no help from the welded together body on that one… we’ll come back to this and discuss further below).

bodies
eek… and this happened with a 1-piece cluster, too.  With a nicer cluster that has removable cogs, the damage would have been much worse.

On the right side is a steel version of that DT350 cassette body.  Unlike the alloy version, it is much heavier – and I expect it to last forever.  Worth noting:  DT Swiss has now released a “Hybrid” version of the 350 hub specifically meant for ebikes.  It includes the steel cassette body out of the gate as just one of its durability improvements.

Get a ‘star ratchet’ rear hub

There aren’t many of them.  DT Swiss, Chris King and Hope are the only big names that sell freehubs with this sort of splined engagement instead of the traditional 3- or 4 pawls.  A splined engagement provides dramatically better contact with the hub from the cassette.  See that nearly-ruined cassette body above?  the stock 18-tooth star ratchet wheels inside went right back into the bike with the new steel cassette body… they were still perfect.  Since DT’s patent on their system ran out, other makers have begun to use it and you can now find star ratchet replacements and complete hub systems on Ali Express, EBay etc.  Myself, I still buy DT Swiss 350’s.  But you can save hundreds with the Chinese hubs.

Uf26dd6f62c374343bc8c305ec79489f7R

Learn how to ride it

I mentioned this briefly above.  With a couple of narrow exceptions (don’t mash the throttle going up a long hill) you already know how to ride a bike that has a hub drive.  thing is, no matter how seasoned and smart you think you are, chances are excellent you are clueless on how to ride a mid drive.

Here’s the short version:  Keep the motor spinning.

Now the longer one:

Keep the motor spinning

Lug it and the torque that is pouring out of the motor will focus on tearing your chain apart, or taco’ing your chainring or rear cog, not to mention generating enormous heat (remember the nylon gears in a geared hub motor?  Guess what?  Mid drives use nylon gears inside too).  Even a BBSHD set to off-road power levels is not strong enough to tear up your cogs or chainrings.  But it can snap a chain that you are mistreating.

When coming up to a stop light, downshift.

Always.  Either that or stay in a gear that is in the middle of your cluster so that when you start up again, the motor can spin up quickly without any brutality being visited on the chain.

When coming up to a hill, downshift.

Always.  Can you guess why?  Thats right so you can keep the motor spinning.  And ‘coming up to a hill’ does not mean ‘already started up the hill’.  Anticipate and shift in advance of the climb.

When you want to go faster, upshift.

But wait until your motor is spinning fast before you do.

When you up- or downshift, NEVER do so under power.

Shifting while pouring huge watts into your chain is an ugly thing.  You will recognize your mistake the instant the result hits your ears.  It won’t kill the chain outright, but as you hear that chain smash from one cog to another you will know your bike hates you very, very much.

You can invest in a gear sensor that will protect you automagically from this.  It installs inline on your shifter cable and, when it senses the tiniest amount of movement, it cuts power for an instant.  The result is a safe shift.  I have them on one of my three BBSHD-equipped bikes and it works great.

But for the two I don’t, I just stop pedaling/freeze my legs, click-shift and then do a single crankarm rotation to seat the new gear at low power.  Result is perfect shifting and only a minor blip in pedaling rhythm.  But that is a learned behavior.

Others have perfected the use of the brake levers as a clutch where they only slightly actuate the lever.  This triggers the safety cutoff which in turn allows a safe shift.  If you are like me and you cheaped out and don’t have safety cutoffs, this won’t work.

Keep chain alignment as straight as you can

Mid drive motors tend to work in a lot wider range than humans do.  So you can leave the motor in a gear that would be too low for your cadence and let it spin away like crazy… it actually likes it that way.  So, this piece of advice is partly about how you ride the bike (i.e. what gears you let it sit in) but also about how you build it.  You really only need three or four gears in the middle of your cluster on a mid-drive-powered bike.  You want them to be the ones that let the motor spin fast.  You also want the cogs the bike is happiest to not be cockeyed, front to back (i.e. bad chain alignment).

On an analog bike you can get away with a lot, since you are only feeding back 150 watts to it.  Feed it 1500 and that sideways-skewed chain will become a saw and chew right through your front chainring and rear cog teeth.  Be smart when you build the bike, and learn in your first outing or two whether there are any problem gears you should stay away from.  There are all sorts of offset chainrings (and 1mm and 2mm shims) available for a BBS02 and BBSHD… they cost money, but spending that money now means not spending it later after you have walked home.

What happens if you don’t do some or all of these things above to install and use a DIY mid drive bike properly?

Well of course it means you go on the internet and blame the equipment.  Its not your fault you used the wrong components.  And its not your fault you didn’t know how to ride it.  Its the mid drive’s fault.

This is the secret message hiding behind a lot of “don’t buy a mid drive” posts on the interwebs.

… If you build with appropriate components, and ride it smart, even a high powered mid drive will essentially last forever.  Yeah sure you will wear out the chain and rear cluster in say three thousand miles, the smallest cog in half that, and the chainrings in 10.  But thats peanuts considering how many miles you put on the bike.  How much does an 11T cog cost (about $6)?

Wrapping it all up

Whew that was a lot of typing.  This article lays out in broad terms the characteristics of each motor type.  It doesn’t get into what kind of riding each is good for.  Lets finish with that:

Direct drive hubs

  1. Lower/legal power:  maintenance free cruiser bikes for paved streets where speed and acceleration are secondary to bulletproof reliability.  Want a bike for Mom?  Your kids (who aren’t future BMX pro riders) A direct drive 250w-750w hub motor is a viable candidate.
  2. High power: Sky is the limit in terms of power:  Light electric motorcycles only thinly disguised as bicycles.  Can range across a wide variety of cycling genres including cargo, dirt and pavement.  But big and heavy.  Single speed is usually a bad choice for offroad/singletrack riding but there are exceptions, in particular the famous B52 Stealth Bomber and similar.  They have so much power they use brute force to overcome the weight issue.  But you’d never pedal one of these things.

Geared Hubs

  1. The Swiss Army Knife of motors.  Not ideal for anything but good for almost everything.  Only runs into trouble under very heavy use, particularly in an area that is all hills.
  2. Their only drawback is maintenance if heavily used.  Semi-annual teardowns to re-grease a high mileage motor is advisable.
  3. Bad choice for singletrack/offroad.

Mid Drives

  1. Best choice for singletrack/offroad
  2. Got hills?  Mid drive.  Strong power delivery without significant weight added to the bike.
  3. Good for hard-use applications.
  4. Arguably the most efficient in terms of power consumption.
  5. Requires the most attention to build detail and demands the most attention and learning from the rider.
  6. Even with proper use and components, more wear and tear on the drivetrain than any other option.
  7. A kid who gets his right hand caught inside the chain of a mid drive is going to be named ‘Lefty’ from that day forward.

The Mongoose Envoy Project

I’ve wanted to build a cargo bike for some time.  I’ve gone halfway a few times, with Frankenbike (front and rear racks, plus a handlebar basket on fat 4.9″ tires, with a 48v, 20a geared hub drive) being the closest I have gotten to the mark.

IMG_20170922_183215
Frankenbike on the job. And yes… that frame really is Max’s MFP Yellow (google it)

When Mongoose began offering a mid-tail ‘urban’ frame — in a complete bike that retails for less than half of anything similar on the market —  I had to jump in and give it a shot.

So here it is, fresh out of the box in its stock form.

IMG_20190917_174431.jpg

Which lasted about a day.

As I write this, the bike has had its cranks and bottom bracket removed, its chain and derailleur detached, the brakes have been upgraded, and of course there’s the double-kick longboard raised upper deck …

IMG_20190923_165853.jpg

… and thats only the beginning.  With that said, this bike is going to be left outside unattended (but securely locked) at local shops.  I don’t want to pour money into its components in case someone manages to make off with it.  So I will be keeping the changes to a minimum – or at least minimum for me.  I’ll be doing just what is needed for improving drivetrain reliability, safety and of course, adding a motor.  And a front rack.  And a suspension seatpost.  But that is it.  Really.

EDIT:  As you can see from the content in the other chapters of this project… all that talk about keeping things under control went out the window.  In the end I decided to just go for it and ended up with what I think is a top line cargo hauler capable of handling 450 lbs+ total system weight (or more… 450 is just how much I have loaded so far) with ease, as well as being an easy commuter.