Get Fixed Bicycle Cafe
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Porirua 5022
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Mid Drive Kit Install Part-3, Bafang BBSHD Basics

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]


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


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


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.


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.


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


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.


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.


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.


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



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.


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.


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 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.


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.


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…