Bafang Install Guide

bafang install -

Bafang Install Guide

*Credit to*

Well, it’s tax return time here in the USA, and for many ebike enthusiasts it is the one time of the year that they indulge themselves, and buy the kit they have been dreaming of for months. Some of those new kits will be a mid drive, and often…the hardest part of the mid drive kit install is removing the stock bottom bracket cartridge. These pictures should give you an idea of what you are up against, so you can decide if you want to tackle this part yourself, or pass it on to a bike shop.


Should I, or Shouldn’t I?

First of all, contact your Local Bike Shop (LBS) because they really need your support. You ‘could’ buy a cheap bike from one of the “big box stores”, but they provide no service at all. Many LBS’s will gladly remove your bottom bracket cartridge for a little as $20 (or only slightly more), which is close to what it will cost to buy the tools you’d need to do it yourself. We all need to show our LBS’s that ebikes are a good thing, and will bring them business.

However, you might be one of those new ebikers that are mechanically inclined, and have a few tools already. If you suspect you might install two or three mid drives (one test ride usually leads to several purchases among your family and friends!), then buying a few more tools and performing this task yourself can be very personally rewarding.


Tools Needed

Double-check what type of bottom bracket (BB) style you have, and also the width of the BB-shell. There will be several variations, but this article will cover the most common Shimano type. The most common shell width is 68mm (2.7-inches), but the bicycle shown here has a 100mm (3.9-inches) BB-shell width.

On some cartridge styles, the crank-arms are held onto the spindle-ends by a hex nut, or a common hex-head bolt (a 14mm socket would be a typical tool to remove the big box store bike crankarms). This bicycle is from the Electra company, and it’s crank-arms are held onto the spindle with hex-socket bolts (sometimes called “Allen” head bolts).




In the pic above, the tool shown on the far left is an 8mm hex bit, with a 3/8th-inch drive interface. On this Electra bicycle, both sides use a common “right handed” thread, so…both are “righty-tighty, lefty loosy”

The tool just to the right of it, is a common crank-arm removal tool. The dark outer part has threads on both the inside diameter and also the outside diameter. The silver part that is threaded into the center of the dark outer part could be described as a bolt. The outer part is threaded onto the crank-arms, and once it is fully seated, you hold it with one wrench, while you drive in the center bolt with a second wrench. This will pull the crank arm off of the “square-tapered” spindle ends.

The tool on the right is the Shimano-style bottom bracket cartridge removal tool. It has 20-splines, and on the far right is the retaining end-piece of the cartridge that it fits into. This tool is shown attached to a 1/2-inch drive “breaker bar”.


Let’s get to it

I recommend you start on the left side. It’s easier to see what’s going on, and once you are familiar with everything, you will have more confidence when moving on to the more difficult chain-side.

You don’t have to remove the pedals to do this, But I started there just to make the job a little easier. If you are removing your pedals first (which you really don’t have to for removing the BB cartridge, but you might be switching these pedals over to the new kit), my pedals take a THIN 15mm open-end wrench (I took an old wrench and “thinned” it on a grinder). The right-side pedal has normal and common right-handed threads. THE LEFT PEDAL HAS LEFT-HANDED THREADS, so…when removing the left-side pedal you move the wrench as though its a normal bolt and you are tightening it, to get it off.

Next (in the picture shown below) the 8mm hex bit is on a common 3/8ths inch ratchet. Hold the crank-arm still, and move the wrench counter-clockwise (lefty-loosy). This bolt has normal right-handed threads.




Once the stock retaining bolt is out, thread the outer part of the crank removal tool into the crank-arm recess. If it is inserted only a couple threads, it will likely strip-out the threads inside the crank-arm (especially if the crank-arms are aluminum), so make sure it is fully inserted. On this model of bike, I was able to insert the crank tool five full rotations.




Now, insert the center-bolt of the crank-tool. Hold the outer part with one wrench, while you turn the center-bolt with a second wrench.




Once the crank-arm has popped-off, it’s time to use the 20-spline cartridge removal tool, shown below on a 1/2-inch drive “breaker bar”. Part of the reason I want you to start on the left side is because…the left-side bottom bracket cartridge retainer is attached with common “right handed” threads. In the pic, you need to rotate the wrench counter-clockwise, “lefty loosey”. If it is on there very tightly, it can help to heat up the BB shell with a hair-dryer or heat-gun, in order to make the shell expand slightly.

On a new bike, this should unscrew without needing to add a long pipe to the 1/2-inch drive breaker bar (in order to add more leverage). However, an older bike will likely have some corrosion on it. This is especially true of steel frames with a steel-threaded cartridge. Here’s a video from “bikemanforu” that shows how rough this can be sometimes.




Now we move on to the chain side. The crank retaining bolt (in the pic below) is just like the other side, the common “lefty loosey” (move the wrench counter clockwise).




Just like before, once the stock retaining-bolt is out, move on to the the crank-removal tool.




In the pic above, back-off the center bolt of the crank removal tool, screw-in the outer part to the crank-arm threads as deep as possible. Hold the part that is next to the cranks, and turn the center-bolt with a second wrench. All operations shown in the pic above are “righty tighty” (clockwise).




DANGER! This is the part where you really have to pay attention. The right side of a common Shimano-style BB cartridge has LEFT-HANDED THREADS! This means to remove it as shown in the pic above, you have to turn the wrench CLOCKWISE. (You could call it “righty loosey”!). Again, the cartridge may be on there very tightly, and using heat to expand the shell slightly may help.

If its taking a lot of force to make any progress, you may find that the splined tool “pops out” before the bike part breaks loose. If this is happening to you, one method to deal with this is to make sure when you were shopping for a splined tool; you get the style that has a large hex around its circumference (like the one shown in the pic below) in addition to the standard 1/2-inch drive square hole on the end. This allows you to run a bolt and washer through the center, which will hold the splined tool tightly onto the cartridge end-cup.

On this particular model of bike (Electra Lux), the bolt thread is a rare 8mm X 1.00 (fine thread), and the proper bolt length to do this when using this model of splined tool is 30mm long with a single 5/16-inch washer (too long would be better than too short, because you could add more washers).




If you are using this method, you can now use a very long wrench to apply exceptional pressure to unthread the remaining part of the cartridge. I mentioned adding heat to expand the BB shell, if needed. You might also consider using some thread penetrant solution.

WD-40 is a common product to use for this. I have also seen “PB Blaster” work well on rusty threads. If you do a lot of work on disassembling rusty mechanical devices, I have also seen a DIY solution of 50%/50% mix of ATF (automatic transmission fluid) and acetone (nail polish remover). Spray it on, and let it soak for a while, and whatever fluid you used will “wick” into the rusty threads.




Although the cartridge fits pretty snugly, it should pull out by hand at this stage.




As soon as the threads have all been disengaged, be VERY careful not to “ding” the threads on the BB shell when sliding the cartridge out.




Examine the inside of the BB shell. Some bicycle models have the downtube intruding into this space just a tiny amount. If your bike is like this, you may need to remove the obstruction with a small Dremel power tool. Whatever you do, protect the BB shell threads. If they become damaged, you may need to take the frame to your LBS and have them “chase” the threads with a BB threading tool.




In the pic above, I am using an angle-grinder to remove the chain-guard support. Notice I packed the BB threads with tissue to keep shavings out. If you don’t protect them they might “look” clean afterwards, but once you begin installing the kit, a few tiny shavings on the threads can make your installation a misery.

I have scars on my hands, and I don’t believe in promoting the “nanny state”, but…I NEVER screw around with my eyes. WEAR EYE PROTECTION. It is the sign of a professional. Do it.




The kit shown is the Bafang BBSHD, which is factory-rated at 1000W, but can be controller de-rated to 750W, depending on the laws in your country. It can run on 48V or 52V, and if using the stock controller maximum setting of 30A, the 52V X 30A = 1560 watts of power.

This particular victim of my abuse is an Electra Cruiser Lux 7D. It is one of the few frames that will allow “some” mid drives to be mounted inside the frame triangle. Even if the drive could only fit to this frame by mounting it under the BB, it still would have worked fine. However, since it fits here OK (while still allowing a very large battery to be mounted in the central frame triangle), I am going to leave it mounted right here.

The Electra company also makes a frame called the Townie, and it is one of the most popular street commuter bicycles in the electric bike kit community. It uses an upright rider posture with a “feet forward” crank position. If using the Townie frame, the drive motor would be mounted just in front of the BB shell, rather than under it or inside the triangle.



I would like to mention again that you can save yourself a lot of time and trouble if you simply pay your local bike shop a small fee to remove the BB cartridge. That being said…thanks for reading, and ride safe!


Part 2


Mid Drive Kit Install Part-2, Matching Connectors from Battery to Controller

We always recommend that when you buy any ebike kit, you get the major components (controller, motor, and throttle) all from the same vendor (also, buy a spare throttle). That way the connectors will all match, and the vendor you bought it from can help you trouble-shoot various issues that might happen. If you mix-and-match components from three different vendors, it can get difficult to get those parts to work together, and the vendors won’t be able to help you when a problem comes up.

The battery, however…is a different story. Kit batteries usually just have two thick wires coming out of them for power…a red positive wire, and a black negative wire (there’s also two skinny wires for the charger). Because of this, it is very common for kit builders to get their new battery pack from one vendor, and the rest of the kit from another. Sometimes the electrical connectors don’t match, and this article will discuss some of the issues and important cautions that you need to be aware of, when you are swapping-in new connectors.


What Connector to Use?

If you don’t already have a preference for a style of connector-pair to use, I recommend the popular anti-spark XT90, for ebike systems up to 3000W. Also, instead of buying bare XT90 connectors, I highly recommend buying “pigtails”. That means the factory has already soldered a few inches of wire to the connector, so the builder only needs to form a “butt splice” of two wire ends.

If you do decide to buy bare XT90 connectors, there is only one piece of advice that I strongly recommend; when soldering wire onto the sockets, make sure the male and female connectors are together, so that the heat from soldering will not cause the pins to “droop” in their plastic housings. This way, their connected status will hold the pins and sockets in perfect alignment until the soldering job is done, and the housings have cooled off.

I mention the “anti-spark” version of XT90 connectors (available in black plug or yellow), it is called the XT90-S. Inside the controller, there are electronic components called capacitors, and as soon as the battery is connected to the controller, there will be a sudden in-rush of current to “fill” the capacitors. On 24V and 36V systems, you may not notice any spark, and even if you do, it will be small. On the popular 48V and 52V systems (or any other voltage higher than that)…there will be a noticeable spark, along with a popping noise. That spark will cause corrosion on the surface of the metal contacts inside the connectors you are using.

Another issue is that some battery pack BMS’s (Battery Management System) will shut down to protect the pack, if it senses a slightly higher voltage than what it’s designed to run. The sudden in-rush current can cause a split-second of a voltage spike, which the BMS erroneously reads as a high voltage, and shuts the battery down.

If the controller is ever dis-connected, the capacitors inside will “bleed down”, leading to another spark when you plug it back in. Most modern battery packs have a large connector for the power to the controller, and a smaller connector from the battery to the charger. By having separate connectors for motor-power and charging, the larger power connector doesn’t need to be unplugged to charge the battery (some DIY packs only have one connector for both charging and controller-power, so they plug-in and un-plug often).

The main characteristic of direct current (DC) electricity that we need to be concerned about is the amperage. If you use high amps (the volume of current), it will need physically large connectors, or they will get hot. In the header pic at the top of this article, the Bafang BBSHD ships from the factory with 45A Anderson Power Poles (APPs). Andersons are very common, and they are adequate for this job. However, they also do NOT yet come with an anti-spark feature, and other ebike controllers can be found with any one of a variety of connectors that are not Andersons.

Andersons are not gendered, and it is physically possible for an inexperienced builder to plug them in backwards (if they are not configured properly). This could cause instant controller damage, and likely damage to the battery too. If you use Andersons, make sure to purchase both red and black, so they are not the same color. Also, once you have verified that they are configured properly, bond them with glue or heat-shrink so they cannot come apart. Hastily re-assembling Andersons that have slid apart, in dim light when you are in a hurry? it can be an expensive mistake, and could even cause a fire.

Luna Cycle is growing in popularity as a battery pack supplier for ebike kits. If you buy a pack from them, they already come with a female XT90-S anti-spark connector. It is traditional for ebike systems to have the female sockets on the battery side, because male pins are more vulnerable to having a metal screwdriver or some other tool accidentally touch them, shorting the battery in a huge spark, and possibly ruining your expensive pack. When they are unplugged from each other, the controller is safe, but…the battery is still dangerous, even when it’s just sitting on the bench…

This means that if you buy a Luna battery, you only need to swap-out the controllers’ male connector to an XT90. It is dangerous to work on the connector for an energized high-amp battery (great caution is required, even if you are experienced), but it is very easy and safe to swap-out the male connector on the controller of your kit, even if you’ve never done that before.

I’m going to cover butt-splicing two wires together using a dry crimp method, and then the soldering method.


Dry Crimp on the Controller Side

Lets start with the controller side, because the controller is not energized when not connected to the battery. Doing this adds a layer of safety until you become familiar with proper butt-splicing. Once you are confident with attaching a male connector to the controller, we can move on to the more dangerous battery side of this operation.

In this first pic below, I have cut off the Andersons, and then I have cut the controller power wires to a length to match the XT90-S pigtails. I “staggered” the cuts, and…doing that is not really necessary for a de-energized system, but…it’s just my habit, so I don’t have a brain-drift when I go to the battery side and forget that I’m not on the controller anymore. If two battery wires are exactly the same length, it increases the possibility that a huge spark can occur. Be professional,  you won’t regret it.




The type of wire-cutters shown are a cheap set of “electrical crimping cutters“. The tip has a cutting edge, and the the base of the jaws (where there is the maximum leverage and power) has a squared-off area designed for smashing crimps, which we will see here soon. [I cut the wires on the Andersons to a long enough length to make an adapter out of them later]

A crimp can be cup-shaped, or a cylindrical sleeve, and….they can be made of copper, steel, or aluminum, etc. In the pic below, I am using what’s called an 18-10 gauge crimp sleeve, which barely fits over a 10ga wires’ thick silicone insulation. I made sure the end of the crimp sleeve that has a “bell shape” is pointed towards the joint.

[both wires shown below have 12ga copper wire bundles. The wire on the left has common PVC insulation which is thinner, the wire on the right has thick silicone high-temp insulation. If you are using wire with thick enough insulation that the 18-10 size doesn’t slide over it, the 14-8 gauge size crimp sleeve is slightly larger if needed]

On the right side, I have placed a section of 1/4-inch heat-shrink insulation over the wire (the 2:1 ratio 6mm heat shrink from Hobby King will also work for 10/12 gauge). Like the name says, when it is heated up, it shrinks down. I now only use heat shrink that is marine-grade (designed for boats), and I always get 3:1 shrink ratio, instead of the common 2:1. This marine grade is lined with heat-activated glue, which makes a very water-proof cover for the joint, and helps improve the joints “pull apart” strength (plus providing excellent corrosion resistance from humidity).

Slide the crimp on first, before stripping the tip, which will make it easier. [The fine copper strands look silver because they have been individually “tinned” from the factory]




On the lower right-side are the professional wire-strippers used to remove a 1/4-inch of the insulation from the tips of the wires to be connected, to expose some of the copper wire strands. Just to the left of it is the razor blade I actually use when I think nobody is looking (yes, I have scars on my hands).

[edit: at this stage, I now recommend TWO sections of heat-shrink be used, because sometimes the crimp develops a sharp corner that might pierce only one later]




In the pic above, if you place the exposed wire strand-bundles next to each other “side-by-side” inside the crimp (example on top), the electrical connection will be poor, and the “pull apart” strength of the joint will be weak. Don’t do this.

Whether you are soldering or using a dry crimp, shove the exposed strand bundle tips into each other so all the tiny strands will have a lot of surface contact with each other (example on the bottom of the pic above).




Slide the crimp sleeve over the enmeshed joint. One end of the sleeve is slightly funnel-shaped, so that end should be pointed towards the joint to make it easier to do this.




This is not the proper tool for crimping wires into crimp sleeves (this is the proper tool), and yet…it works great for 10-12 gauge crimps, and is affordable. Use your best “Kung Fu grip” and smash the crimp sleeve until it’s flat. I purchased copper crimp sleeves, but the job of the crimp sleeve is only to hold the enmeshed copper wire stranded bundles together. Steel or aluminum will work just fine, because the crimp does not carry current. In fact, I think steel would hold the crimp better, instead of relaxing over time.




In the pic above, we have the crimp sleeve mashed flat. Now slide the heat shrink over the joint and heat it up.




There are two concerns that are sometimes voiced by builders who have never used a dry crimp on a butt-splice. The first is whether or not it helps or hurts the joints’ conductivity and resistance. If you use a high strand-count wire, and then intermesh the strands on both tips with each other…resistance is very low and conductivity is great. As an experiment, solder two wire stubs together, and also dry-crimp two wire stubs together…then you can measure the Ohms of resistance with a Digital Multi Meter (DMM) to see for yourself.

The second concern is “pull apart” strength. You shouldn’t be yanking on electrical wires, but just to put any concerns you may have to rest…the pic above shows me holding the BBSHD in the air by one 12ga wire that is dry-crimped to the positive power wire to the controller. This is the same exact dry crimp from the last several pics above. Try it on some scrap wire first, and then try to yank them apart.

Even if you prefer to always solder an electrical joint, by having the proper electrician cutters with crimping jaws along with a few crimp sleeves means that…you can do repairs in a remote area with no electricity for the soldering iron.


Soldering a Butt Splice

In the pic below, I have staggered the lengths of the wire-stubs on the XT90-S pigtail. Then I used my razor blade professional wire strippers, to strip the insulation off of the tip of the red/positive wire. I then cut up some scrap wire so I can take several fine strands of copper wire and twist them together, then interlace them into a loop. Instead of wasting good 12ga ebike wire for this, I use some scrap wire I rescued from the trash [if you see an old vacuum cleaner at the curb on trash day, I see an electrical cord with a lot of copper in it. The bigger the vac, the fatter the free wire]




Slide the wire-loop over one 12ga stub, and the heat shrink over the other. Then, just like before [whether you dry crimp or solder] shove the multi-strand tips into each other. Then you position the loop in the center of the joint, and pull the ends of the loop to tighten it over the joint. The loop is not very strong, but…it is “just strong enough” to hold everything together until it’s properly soldered. This simple tip works great to make your soldered butt-splicing jobs easier, and it was suggested to me by endless-sphere member “Amberwolf”.




You can wrap the loop ends around the joint some more and then solder, or…solder first and then snip off the hanging ends. Either way, you will need a high-watt soldering iron with a fat tip. A thin “pencil” style soldering tip will cool off way too fast when it touches a fat wire. I like to put the fat soldering tip under the joint and lift up slightly, then feed the solder downwards. Put a dab of solder right where the soldering iron tip touches the joint, and that will immediately improve the heat connection between the tip and the joint. [don’t do this on carpet, and don’t ask how I know that]

I found this affordable Weller 100W soldering iron [with the thick tip option] in the “stained glass window” section of a crafting warehouse.




As you can see below, when the copper wire in the loop turns a silver color, that means the entire joint is saturated with solder. Make sure to let the joint cool before sliding over the heat-shrink. If you try to slide it over while its still hot, my heat-shrink has heat-activated glue inside, and it will stick halfway to the target. Blow air through a straw if you are doing a lot of these, and want it to cool down faster…




This is the part where I’m supposed to tell you to buy a professional “heat gun” to activate the heat shrink insulation, but…I always use a butane-flame barbecue lighter (which can throw a small flame almost directly downwards or sideways), and everyone I know also uses lighters. Be safe and don’t burn yourself or start a fire, m’kay? (just in case you actually do want to use the proper heat gun, the one I have seen used the most is the $22 Wagner HT1000, which can be found on Amazon, or any one of the big hardware stores)




In the pic below, the male XT90-S “connector upgrade” to the controller is completed. Notice that one side of the plug is squared off, and the other is rounded. This feature “polarizes” the connector so you can’t accidentally plug it in backwards. For instance, if you are in a hurry in dim light [or have been drinking lots of beer…I’m looking at you, Australian ebikers].




Andersons are OK, but….in my humble opinion (IMHO), anti-spark XT90-S’s are better. Lots of chargers use 45A Andersons, so keep these to make adapters.


Connectors on the Battery Side

Batteries are dangerous to work on. Even if you are not physically burned (KFF, for Kentucky Fried Fingers), your expensive battery can be fried in a split-second of carelessness. Even if a battery is low, it still holds a tremendous amount of power. Ebike batteries in particular use high-amp cells, so a short-circuit that is directly connecting the two power wires will cause a huge spark, with an incredibly bright flash that can damage your vision. Maybe your battery pack might even start pouring out lithium smoke! Here’s some VERY IMPORTANT tips:

Only cut one wire at a time. It’s easy to forget…cutting both at the same time will short-circuit them through the cutters.

Stagger the cuts so they are not the same length, as an extra safety measure. Its free, and it can’t hurt…

Cut one side, then complete the crimping or soldering and insulating of that new connector wire…BEFORE cutting the second wire.




In the pic above, I cut one wire of a fully charged battery with metal cutters, but that’s OK as long as you only cut one wire at a time.

In the pic below, I’ve cut the old connectors red/positive wire, and then soldered the red/positive of the XT90-S female connector on…and I am about to activate the heat shrink insulation.




Once the red/positive on the new connector was soldered and covered with insulation, I was free to cut/solder and insulate the black/negative side. The thin twisted red/black wires are for the low-current charger, and the thicker wires are for the full current to the controller. If you add longer wires to the power connection, make the wires and connector larger than stock, so they will run cooler than normal.




[If you need an anti-spark connector that carries more power than 90A/3000W, I have read of good results using AS150’s (Anti-Spark, 150A). XT90-S’s can fully seat 12/10 gauge wire, and AS150’s can accept 9/8 gauge. A 9ga wire has double the copper mass cross-section of 12ga]

Now at this stage, you should be able to plug-in and bench-test your new kit, and that way you can sort out any issues before you finish going through the full installation. Speaking of the kit installation, this is a 3-part series for the BBSHD, but…part-one was written so that it could be used as a stand-alone tutorial for removing the bottom bracket cartridge, regardless of the mid-drive model you like. Here, in part-two…I wrote it so that it can also be used as a stand-alone tutorial for mating connectors between any common controller and battery.

Part 3

This article will cover the basics of unboxing your new Bafang BBSHD mid drive, and installing it on your bicycle. This is part three, of a four part series. First we covered removal of the bottom bracket cartridge, which could apply to just about any model of mid drive. Next we covered mating the battery connectors to the controller, which can help any new ebiker, even hubmotor customers.

I thought I was only going to need to write three parts, but now that I have gotten my personal BBSHD running, and I’m preparing to take the pics for this pictorial…I realized there are many useful bits of information that I wanted to understand as soon after I reached the basic operational stage (so, I imagine that many of our readers would appreciate info on that too).

Part four will cover BBSHD customization of the programming, upgrading to the larger color dashboard, listing some desirable accessories, and several other items that I feel will dramatically improve the rider experience for all the new Bafang mid drive owners.


Let’s get started!

I am rushing this first half of this article just to get it out there, since many BBSHD customers did not start out as “bicycle” people, and are unfamiliar with some of the tools and terms. If you have been working on bicycles for many years, you probably don’t need this tutorial at all. However, even people who are new to the bicycle game will likely be reassured once they see the pics of what is involved, and can tackle the install with more confidence.

This article assumes you have already read and seen the pictures from part-one (click here) and also part two (click here). So…now we pick up where part two left off…

Tools needed

2.5mm hex wrench

3mm hex wrench

4mm hex wrench

5mm hex wrench

8mm hex bit [with 3/8ths drive ratchet]

15mm open end wrench [for pedals]

locking ring spanner

bag of thin 8-inch long zip-ties

[more tools will be added to this list as needed until the pictorial is finished]


100mm wide bottom bracket shell

A 100mm wide bottom bracket shell


The bottom bracket (BB) of bicycles are made in several widths. The most common by far is a 68mm (2.7-inches). You will occasionally find a 73mm, 83mm, 100mm, and 120mm. The 100mm (3.9-inches) has recently become popular for fatbikes (like this one), and some off-road bicycles. For a variety of reasons, I chose to mount a 120mm kit onto a 100mm wide bottom bracket, and I will take up the slack using Luna Cycles aluminum spacer rings. Now that I’ve done this, I would be completely comfortable buying a 100mm kit for a 100mm BB.

I would not recommend installing a 120mm kit onto a bicycle with a 68mm BB shell, but there should be no problems if you’d like to mount an 83mm or 73mm kit into a common 68mm bike (which would require the addition of spacer rings, as I have done here below).


The BBSHD drive unit

The BBSHD drive unit


As you can see, back in part two we soldered a male XT90-S connector (yellow) onto the controller cable. Because I have decided to mount the motor inside the frame triangle, I had to grind away some of the fin material off of the shell, and I also had to bang a serious dent into the seat-tube in order to do that (not recommended). For a normal installation, the motor sits in front of a straight downtube, and no modification to the drive or frame is necessary.


Inserting the drive

Inserting the drive


Take the drive unit, and insert it into the bottom-bracket (BB) shell from the chain side. The OD of the sleeve is 33.4mm, and the ID of the BB shell (on my model of frame) is 33.6mm, so it will be snug. Be careful not to ding any threads on the drive or the BB shell. The dust and scuffs in the pic are because this is the second time I installed it after the initial test run.

If you look closely, this drive is marked 750W, and the controller can be adjusted to make it a street-legal PAS ebike, depending on your local laws. For off-road, it can be de-restricted to a max of 52V X 30A = 1560W.


The retaining bracket and bolts.

The retaining bracket and bolts.


Locate the retaining bracket and two bolts, which use a 5mm hex wrench. Notice the radial ridges pressed into the side of the bracket. These are designed to dig into the side of the BB shell edge, and hold the motor in place, instead of the drive rocking back and forth. Make sure these ridges face the bike when installing.

When the motor is applying power, it will try to pull up towards the downtube. These ridges only attempt to keep the weight of the motor from drooping down.

Also, one of the factory threaded holes that the bolts go into was not deep enough. You can cut one of the bolts shorter, or add washers to one of them. I found a nut that was just a hair too large to thread on, and used it as a thick washer. It still left more than enough engaged threads to make a solid connection. [edit: I now seem to remember there were some short sleeve spacers in the kit that could have performed the function of the nut in the picture above, which is acting as if it is a thick washer, and possibly also to allow a 73mm kit to fit onto a 68mm BB].


tightening the bolts on the retainer.

tightening the bolts on the retainer.


In the pic above, one bolt has been tightened by a 5mm hex wrench, and the other bolt that requires some type of thick washer or spacer has not been tightened yet. The thread for these two bolts is a common M6/6mm X 1.0


The locking ring

The locking ring


In the pic above, I have threaded-on the locking ring. I spun it all the way down, and then I backed it off two full threads, in order to see how many spacers I will need. The tape measure is showing I need a minimum of 20mm (about 3/4 of an inch, the difference between the 100mm BB shell width, and the 120mm kit). I will slide-on about 22mm’s worth to allow for compression after tightening. These spacer-rings are available in 1mm, 2mm, and 4mm thicknesses.

[note: if your drives’ reduction housing hits the front of the chainstay on your model of frame, it can prevent the reduction side of the drive housing from fully seating perfectly flat against the right side of the BB shell. It is vital for the drive to be firmly seated flat up against the BB shell, so some of these spacer-rings can be located on the right side to shift the drive outwards, so the housing doesn’t hit the chainstay part of the frame]

Once everything has been road-tested to my satisfaction, all threaded parts will be backed off and I will apply “thread locker” fluid, which is a type of glue made specifically to prevent nuts and bolts from coming loose.


Re-attaching the crank arm.

Re-attaching the crank arm.


In the pic above, the 22mm stack of spacers has been installed (3/4’s of an inch thick), the locking ring has been tightened down, and I am about to use a 3/8th ratchet wrench and my 8mm hex bit to tighten down the crank arm onto the square-taper spindle tip. The bolt is steel, and the spindle is steel, so…you can really tighten it very firmly.

In fact, since this crank arm is aluminum, any looseness at all will result in the crank-arms’ socket being permanently damaged when pedaling. It is not just a “good idea” to tighten it down firmly, it is vital to do so every time you re-attach a crank-arm.


Attach the stock drive-sprocket.

Attach the stock drive-sprocket.


Find the five small hex-head bolts, and use a 4mm hex wrench to attach the stock drive-sprocket. If this part had a separate central “spider” and toothed part, it would be called a “chainring”. The threads on these five bolts are 5mm X 0.80, which is the “standard” size M5, found at most decent hardware stores.


Attaching the other crank-arm.

Attaching the other crank-arm.


Just like the other side, tighten down the crank-arm bolt very firmly every time you re-assemble these.


Putting the chain back on.

Putting the chain back on.


Since I am young and handsome, this enormous hairy hand shown in the pic belongs to my hideous assistant, who escaped from a institution for the criminally insane.


The controller main connector.

The controller main connector.


Its time for the first “bench test”. Sorry for the blurry picture, I will take another this week. Find the two connectors with eight pins. These connector housings are not keyed, so be very careful inserting them together, so you don’t bend any of the pins. There is one empty pin location (out of a possible nine), so they cannot be plugged-in the wrong way, but…the lack of a housing key-slot means you can damage this part very easily.


The eight-pin connector arrows.

The eight-pin connector arrows.


In the pic above, the outside of this connector-pair has two arrows cast into the plastic, but they are not easy to see. I used a CSI computer program to “enhance the pixels” of the light reflecting off of them. Line these up before connecting them every time, don’t try to do it by “feel”, or you will eventually regret if you do that.


The thumb throttle.

The thumb throttle.


The two E-brake connectors look similar to the 3-pin hand-throttle connector, but the thumb-style hand throttle provided has the female sockets on the throttle side, with the male pins located on the controller side (the E-brakes are the opposite). These housings are properly keyed, to ensure they can be easily inserted in the correct orientation without any danger of bending the tiny 5-volt pins. I was also pleased to see that the throttle connector housings have a pliable water-resistant sleeve.



The battery connectors.

The battery connectors.


In the pic above, you can see the XT90-S “anti-spark” connectors, with the female on the battery side, and the male on the controller side. If you ever decide you need to make this cable-run longer, add wire to the controller side. The battery is always energized, and has a huge amount of stored power, even when it is considered “low” by the controller. A simple mistake can cause a fire, badly burn your fingers, or damage the expensive pack. I work on these kinds of batteries all the time, and even with my experience? when I have a choice…I always work on the controller wires.


The ON/OFF switch and control display.

The ON/OFF switch and control display.


Now for the magic moment. Press the center button on the ON/OFF controller for about two seconds. If everything is working right, and your battery is charged up, the display will fire-up and look like this.

Make sure nothing is touching the rear tire, or leaned up against it. 99.9% of the time, the rear wheel is about to take off very fast, so be aware of that.

Spin the crank-arm, and at about the halfway around point…the drive will likely start to apply power from the PAS signal. Next, pick up the thumb throttle and give it a try, too. If both of them made the rear wheel spin, then…your face should be smiling very hard right about now. Exercise caution with how hard you are smiling, it can damage the muscles in your face if you are smiling harder than your face is used to.


What now?

There has been a great demand for this part of the mid drive DIY series, so I am publishing the first half of part-three here and now. Many of you can take this installation to the finish from here, without seeing the next few pics. I will be adding the second half of part-three in just a few days. It will include:

Mounting the battery pack in the frame

Adding pedals [needs a 15mm open end wrench for most common pedals]

Connecting the two E-brakes, so applying the brakes will also cut the power

mounting the dashboard and throttle to the handlebars

[the stock dashboard is held on by two bolts that use a 3mm hex wrench, and the thread is a common M4/4mm X 0.7___Also, the on/off button housing is held on by a single tiny nut and bolt. It uses a 2.5mm hex wrench, and the thread is not easy to find in a common hardware store, it is a M3/3mm X 0.5, I wish they had used the same slightly larger bolts as the dashboard]

Routing the wires and zip-tying them to the frame

Mounting the spoke-magnet and sensor, so the controller can tell how many RPMs the wheel is spinning at.

Programming the controller for the diameter of tire, so the speedometer works

Drinking heavily, and rambling-on incoherently…