I have done a lot of things in my life but the one thing I find more relaxing, rewarding, challenging, interesting, and mentally stimulating is the building of bicycles, electric or otherwise. Did you know riding a bike is like riding a gyroscope? It is not magic that keeps us balanced on two wheels (although it may seem like it at times) it is physics. Sailboats were developed thousands of years before chain driven bicycles and yet the complexities of sailing are infinitely more complex than a bicycle. The very idea of a person balancing on two very small contact patches of two wheels while propelling forward was impossible to invision. Yet, we do it everyday on our bikes without ever giving it a thought. Riding a bike is like flying without ever leaving the ground. Building a bike, is to participate in the magic that brought the bike into reality just a century ago.
I hope this section provides enough information to allow you to build your electric bike successfully. A successful build must be able to stand the test of time; remember that when you have finished. A successful build is one where the motor has been installed in such manner it does not come loose in the future. A loose motor can tear out the wires and cables and damage the frame. The battery must be mounted on the bike in such a manner it does not come loose and damage the frame. The battery itself must not come into any moving parts on the frame and the battery case be compromised. The point is, when your build is finished and everything looks good and you are pleased with your accomplishments, understand the true arbitrator of a successful build is time. Mother used to say, "Time will tell." No build can be called successful until time has had a go at everything you have done in the construction of your electric bike. If you used inferior parts...time will find those parts and cause your build to fail. If you took shortcuts on your build...time will determine if those shortcuts compromised quality or safety.
In the end, I hope you will look back in pride at your contribution to the knowledgebase of transforming a standard bike into an electric bike. Perhaps you will find a new, different, better way of securing a motor or mounting a battery. Converting a bike to electric is as much art as it is mechanics and like all good art it requires patience, determination, and the ability to glimpse the future.
Good luck, be careful, and enjoy the experience
Alvin Carpenter, CEO
Island City Bikes
Alvin Carpenter, CEO Island City Bikes
The best way to remove a bottom bracket is to take your bike, or bike frame, to your local bike shop and have them do it for you. That way you do not have to purchase any of the tools required for bottom bracket removal, you do not have to worry if the bottom bracket is frozen in the frame, and it only costs around $35. Leave the cranks on the bike when you bring it to the bike shop as they will remove those also. This one small bit of advice will make you motor install a lot more pleasurable. At our shop we remove bottom brackets from bikes everyday and we know the difficulties one can (will) encounter.
This bb shell is the perfect size for the Bafang motor. Some will be larger and will require adaptors. Some adaptors you can purchase while other adaptors will have to be machined.
Sometimes, after the bb has been removed there will be obstructions in the bb shell. Any obstructions in the shell will have to be removed prior to installing the motor. An obvious obstruction is the small screw on the bottom of the shell that hold the cable guide. A more difficult obstruction will be inner weld. When the downtube, chainstays, and seatpost are welded to the shell sometime the shell will become slightly deformed. This has no effect on a bottom bracket but it will block the installation of the motor.
There are a number of different tools that can be used to remove the materiel in she shell that is blocking the motor. A half round file will work but requires a fair bit of time. Concentrate on the weld joints in shell and smooth them out one at a time. Sometimes it can take up to an hour of filing so be patient.
Another tool is a Dremel. A Dremel will speed up the work but you have to be careful you do not damage the threads on the shell. You might want to protect the bottom bracket threads just in case you wish to remove the motor and reinstall a bottom bracket in the future.
Many times people will encounter a problem at this step. The problem being the axle on the motor is too short. How does this happen? Measuring the bottom bracket shell can be awkward due to its shape. You may think it was a 73 but it turns out the shell is a bit longer than 73mm. First, look at how many threads are available to lock the motor down with the fixing plate in place. It only takes about three threads. Do not worry about the locking cap as it is not necessary if the motor is correctly locked down. Still not enough threads available? There are a couple of options. The first option is to use a motor brace instead of the fixing plate.
This is the downtube motor brace. There is also a chainstay motor brace but it is not our favorite. The motor brace is much thinner than the fixing plate and this is used in lieu of the fixing plate. It might just give you that extra thread you need to fix the motor in place. The fixing plate is attached to the bottom of the downtube by Rivnuts, or a rubber encased hose clamp. Some bikes will have water bottle inserts on the bottom of the downtube already in place. Many touring bikes have this feature. If you are one of the lucky one to have this insert, attach the motor brace to the frame using the water bottle insert. If, there is still not enough threads then there is a third option.
This may seem a bit extreme but it is not at all. However, you do have to be careful. You do not want to cut into any welds, and it has to be level! If it is not level it can cause the motor to sit in a position that can cause it to bind. What if you cut off too much material? Use your spacers if that is the case. If possible, cut from the side that has the chainring. I know others suggest cutting from the non drive side but if you cut from the drive side you can improve your chainline in the process. We cut from the drive side first, and as we cut we constantly check to insure the chain ring will not hit the chainstay. Then we move to the non drive side and grind until we have sufficient threads for the installation of the motor.
This is the locking cap that goes over the top of M33 fixing bolt. Sometimes there are not enough exposed threads to use this cap and if that is the case then toss it as it is more decorative than anything else. We use it when we can as it makes for a cleaner finish. NOTE: Loctite is not required on either the M33 locking bolt or the locking cap. If you do feel compelled to use Loctite, make sure it is Loctite "Blue" and not Loctite "Red."
Make sure the motor housing is not touching the chainstay, or any part of the frame. This is very important. If the motor housing touches the chainstay the motor will sit askew and will reduce the life of the motor and the drivetrain of the bike. Use a 1mm spacers to move the motor out just far enough to clear the chainline. Remember, when you move the motor out, you change the chainline. You want the motor as close to the chainstay as possible.
This is an example of a poor chainline. This chainline will cause the chain to fall off the chainring and prematurely wear out the entire drive train. Establishing a proper chainline can be one of the most difficult tasks of using a mid drive motor. The power of these motors will exploit any discrepancies it can find. Give it nothing to find. There are few options you can use to move that chainline in. You can use a deep set chainring like a Lekkie, or you can lock out the final cogs using the set screw.
This is a picture of a Lekkie chainring. These cost around $75-$100 and are worth every cent. The offset of this ring moves the chain back towards the frame of the bike and establishes a straight(er) chainline. The stock chainring has very little offset and about 30% of the time they are just insufficient at allowing a functional chainline. It does little good to go through all the work and expense to convert your bike to electric only to have you chain continually fall off the chainring. A stock chainring come is 42T and 46T. We always use the 42T for greater torque and less stress on the motor while climbing. The Lekkie chainring comes in many sizes, from 28T to 52T.
Here you can see the chain goes straight from the middle of the rear cassette to the chainring. This is what we like to see., equal distance between the smallest cog and the largest cog. Note; If you have a bike that is called a "one by" then you may encounter more problems with chainline. A one by bike is a bike that typically has a very small single chainring up front and 11-12 cogs in the back. This style presents the most problems with chainline. However, because the range of the cassette is so large it is reasonable to lock our the last (and sometimes the second to the last) cog. This is done via the small set screw.
This is a picture of the motor sitting on a hydraulic brake line. In this instance there is little choice other than using a hard rubber spacer. The Bafang motor torque is always forward and it likes to rest on a solid foundation, like the downtube. That is why it is important to use hard rubber as a spacer. Otherwise the motor will begin to rock slightly and then come loose. We have used 1/8" aluminum in the past as a spacer, and that works also but a hard rubber spacer with a motor properly torqued will do the job.
Hint: We buy auto heater hose to use as spacer material. We take the hose, cut to length, and then split it down the middle. Heater hose is very strong material that is built to withstand the high heat environment of an automobile engine.
On some bikes the crank arm on the non drive side will come into contact with the chainstay. Before locking the motor, take one of the two crank arms that came with the kit and put it on to see if will hit the chainstay. As you can see from the picture above, the crank arm has sufficient distance from the chainstay. If it does hit the chainstay you will have to order a set of Bafang offset crank arms. Lekkie products also makes an offset crank arm but be prepared for price shock as they are very expensive.
Before locking the motor place the chainring on the motor and check to insure clearance. The chainring cannot touch the chainstay. The goal is to get the chainring as close to the chainstay as possible without touching it. If it touches the chainstay, pull the motor out and start with a 1mm motor spacer and then re install. If it is still touching, repeat with a second spacer. While moving the motor out you will be moving the crank arm on the other side closer to the chainstay. Make sure you check that crank arm each time you move the motor. If it crank arm does hit the chainstay, move the motor back to where it is clear then go ahead and secure the motor. Remember, the chainring is going to come into contact with the chainstay, that will need to be addressed by using spacers behind the chainring.
Any spacer to be used to move the chainring away from the chainstay has to be one made specific for that use. The inner diameter has to fit either the BBSHD, or the BBS02 Bafang motor. They are not interchangeable. Always start with the thinnest spacer and move to the larger one. Nearly always. the thickest spacer you will use is a 2mm spacer. NOTE: The bolt used to attach the chainring to the motor is a M5x10mm socket cap. If you use a 2mm spacer I recommend you attach the chainring using M5X12mm bolts as the M5x10 are too shallow.
Look closely and you will the motor is resting on the corner of the bolt housing. We have seen this setup on the bikes people bring us for repair. When the motor is NOT resting on the bottom of the downtube (for full support) and istead is resting on the sharp edge of anything that sharp edge will eventually puncture the frame. Just gentle vibrations will cause that sharp edge to eventually damage the frame. To prevent this, take a crosscut file and file enough material off the bolt housing until the motor is sitting fully on the downtube. On this bike, it took about 20 minutes of hand filing to get the desired clearance.
Full suspension bikes have pivot points and it is very important these pivot points are not restricted. Before locking down the motor do a close inspection of all the pivot points to insure they do not come into contact with the motor. It is common for the fixing plate to touch the bottom pivot point. If this is the case, take a file and file the fixing plate until it gets the necessary clearance. Fixing plates are made of steel so it takes a bit of work to file them down.
The best way to understand what moves on a full suspension bike is to let all of the air out of the shock. Once all the air is released then the bike will move freely on all the pivot points. This makes cabling a lot easier and checking to see if the motor is coming into contact when the frame is fully compressed. NOTE; In order to inflate the shock you will have to use a special high pressure pump.
Here you can see both the shift cable and the brake cable running straight in the path of the motor. The motor cannot be allowed to crush or impinge these cables. This comes about through the use on internal routing of the cables. Internal routing of cables has become very popular and is found on many newer bikes. What do you do when the motor rests on these cables? There are a couple of options. The first, and best option is to remove the cables from the frame and reroute them on the outside of the frame. Be sure to use cable guides and cable stops when you reroute your cables. If your bike has hydraulic brakes DO NOT move this line outside the frame. Try to move the line over as far as possible towards the non drive side. There is often just enough clearance for the cable to pass through the opening between the motor housing and the bottom bracket shell.
A Second option is to put a small hard rubber spacer between the motor housing and the bottom of the downtube to keep the motor off the cables and then tighten the motor. If you choose this method be sure to periodically inspect the motor to insure it has not come loose.
Now, we should be ready to lock the motor in place. Lines, are clear or have been rerouted, chainline looks good, motor housing not touching chainstay, enough threads for M33 to engage, motor brace ready if needed, and off we go.
Locking down a motor can be hazardous. Whenever a lot of force is being applied to any screw, nut or bolt, there is the chance the tool may slip free. When that happens serious injury may result. Always check to see where your hand may end up if the tool slips. Always work away from your body.
Note: When you run your cables make sure they are not under the motor or anywhere else they might be crushed or cut if the motor does come loose. Any motor that is secured properly will stay in place for the life of the bike. The reasons motors do come loose is because the Bafang wrenches are just not adequate for the task. By the way, they are not Bafang wrenches, these are aftermarket tools. Bafang does not make wrenches.
Most will have purchased a Bafang spanner to lock down their motor. The good news is that spanner will work sometimes. The bad news is that it does not work that well and sometimes not at all. For example, if your bike frame is steel or titanium you will need a lot more torque to press that steel fixing plate into the bottom bracket shell. The picture above is a special socket, available online, that allow the use of a large wrench to tighten the not that holds the motor in place. At our shop we use power tools to lock the motors in place.
Every now and then I read online that the weakness of the Bafang mid drive is that they come loose. No, that is incorrect. Poorly installed Bafang mid drives will come lose due to the tremendous torque of these motors. Properly installed Bafang mid drive motors will hold in place for the life of the bike.
Please, if you motor has come loose, stop riding the bike and bring to our shop and we will set it right using our power tools.
An electric bike will not work with a worn chain. One can ride a bike with a terribly worn chain and hardly notice but once you add a motor the worn chain will make the bike unopertable. If, after finishing you conversion to electric, you take your bike for a test ride and you hear a loud popping noise coming from the rear of the bike...that means your chain is skipping over the teeth of the rear cogs! 70% of the chains we see need replacing prior to conversion to electric. How much do chains cost? A chain can cost anywhere from $15 to $75. For most bikes a chain will be around $25. Can you install a chain yourself? Yes, you can.
Pictured above is a chain breaker and chain link remover (quick link) and installer. Both tools can be purchased for around $12. First, remove your old chain and place it on the floor. Then take your new chain, lay it alongside the old chain and cut to length. Note: the links on the chain you are replacing are a bit further spaced than those on the new chain so it will not line up perfectly. Remember, the bushings and rollers on the old chain are worn and that is why they are further apart. This is what is called "chain stretch." Of course, the chain has not stretched (the chain plates are the same) but the chain is longer so it gives the appearance of stretching.
Every bike that comes to our shop for conversion to electric we remove the rear cassette, clean and then inspect for any damage. In the picture above we found a broken tooth. Under human power this would matter little and would have little impact on performance. Under the power of the Bafang 750 it would affect the quality of shifting. Replacing a rear cassette can be difficult and it requires two specific tools for removal and installation.It might be best to simply remove the rear wheel and take it to your local bike shop and have them remove and replace the cassette. When you replace the cassette make sure the largest cog is no smaller than 32T.
Now is the time to replace the shift cable to the rear derailleur. Shift cables, and shift housing, are what determines how smoothly and quickly you can shift up and down the rear cassette. Upshifting is not a problem as you are literally pushing the derailleur up into the next geat. Downshifting relies on the strength of the spring in the derailleur to pull the chain into a higher gear. If the cable is rusty, or the cable housing is corroded, the spring in the derailleur will not be able to pull the cable to the next gear. The Bafang motor will not wait on a slow derailleur and the result will be a very underperforming electric bike in terms of shifting.
We often see shift housing that is crushed (above), kinked, or rusty. Never install a new cable in old housing as the two work together. Cable housing has to be the number one overlooked component on a bike. Cable housing is more than a simple conduit for the shift/brake cable. They are remarkably made using a number of different innovations for both brake and shift housing. Shift housing has small wires running parallel to the cable in order to prevent compression under load. Some shift cable housing has a plastic liner for smoother operation. Although, we prefer to use standard shift housing with no liner as it provides smoother shifting (in our opinion).
If you have mechanical brakes (non hydraulic) then you have brake cable housing. Inspect the housing for any rust, corrosion, kinks, or kinks at the end cap (common). Brakes work on a return spring and when the return spring grows weak the pads have a tendency to drag on the rim and are hard to adjust. IF you decide to replace the cable housing make sure you purchase the very best as it will last a very long time.
Note:If possible, use compressionless housing. It costs a bit more but in reducing compression it makes the pull of the lever to the brake caliper much more responsive.
Adjusting your shifting is very easy. First, click your shifter until it is in the lowest gear. Second, turn the barrel adjusters all the way in, both at the derailleur and up at the shifter. Then pull the cable hand tight (not too tight) and lock down using the fixing nut. Shift through the gears. If more slack appears, loosen the nut, remove slack, and tighten the nut. Shift again...hear noise? Now, you turn the barrel adjuster (at the derailleur, or at the shifter), until the noise goes away. That's it! Pretty simple. Some prefer to start at the middle of the cassette, others start at the first cog. Whereever you start you will get the idea of what is happening. Once you learn to do this you can do your own tun ups.
Derailleurs have a low and high limit screw. These small adjusting screws "limit" how far the derailleur can travel. The "H", or high limit screw keeps the chain from falling off the smallest cog while the "L" screw keeps the chain from falling into the spokes. Super important these are set correctly. It is my recommendation you do not tamper with these screws and if you do feel so compelled I recommend you follow this tutorial: Park Tool Rear Derailleur Adjustment.
A. "B" adjustment
B. High Limit screw
C. Low Limit screw
What does this picture have to do with brakes? Nothing...I just like the picture.
Now, more than ever you are going to need brakes that function and function well...every time. There are many types of brake system and it would be impossible to cover them all but typically they fall into two main categories; rim brakes and disc brakes. Rim brakes are when a caliper grabs the rim the bike in order to slow or stop. Rim brakes have been in use for over a 100 years. They are inexpensive, simple to maintain and adjust, and provide a powerful stopping force. Disc brakes are relatively new to road bikes and are more expensive, wear brake pads out quickly, can be very noisey, difficult to adjust, heavier, and they also are capable of providing a powerful stopping force.
This is a mechanical cable actuated disc brake caliper. Some of these are so poorly made it is impossible to install/adjust without rubbing on the disc rotor. Wholesale on this caliper is around $3, so that should tell you all you need to know. That said, there are excellent mechanical calipers such as those made by Avid, TRP, Shimano, and others. The Avid BB7 is one of our favorite.
All mechanical disc calipers need periodic adjustments! If you have disc brakes, learn how to keep them in adjustment as it is very easy.
If you want to have disc brakes you cannot beat hydraulic disc brakes. With hydraulic brakes they is never a need to adjust the pads. The standard used to make hydraulic brakes is ten times (hyperbole ) that of mechanical brakes. The caliper itself has to be designed and manufactured to withstand the pressures of a hydraulic system without leaking. Whereas, a mechanical pull system is held together with nuts and screws.
When it comes to disc brakes....there are well made disc brake systems that work very well in all riding conditions, are simple to maintain, can be hydraulic or mechanical, and...wait for it...they are not inexpensive. Then there is all the rest. When I say "all the rest" I mean do not waste your time on disc brake systems that are completely inadequate out of the box. I would rather have poor rim brakes over poor disc brakes every times as poor rim brakes are easy and inexpensive to upgrade.
If you have mechanical disc brakes it is important you learn how to adjust the inner pad. On the back of the caliper there is a hex nut (sometimes it will be a torx nut, or hand manipulated) that has to be turned to move the inner pad out. If you do not make this adjustment eventually the brake rotor will be pushed on to the rotor itself (metal on metal) which will reduce braking performance drastically and will ruing the rotor and possible the caliper. It is very easy to do; Use a 5mm hex tool, reach through the spokes and turn the hex nut until the brake pad touches the rotor and then back the nut off until there is a slight gap.
To adjust the outer brake pad, turn the barrel adjuster on the caliper (or at the brake lever) until the brake pad touches the rotor and then slowly back off until there is slight clearance between the brake pad and the rotor. Sometimes, you will have to loosen cable bolt and remove the slack from the cable and then tighten.
This is the most common style of brakes we see come into our shop. They are very effective brakes and are simple to maintain and adjust. NOTE: Make sure the brake shoes are not coming into contact with your tire as this can lead to a blowout. These brakes often need to be centered as over time the spring that centers them grows weak. On each arm of the caliper there is a small phillips head screw. Turn this screw clockwise to tighten the screw and counter clockwise to relieve the tension on the screw. Do this on both side and PUMP the brake lever a few times every time you make an adjustment. Pretty simple.
Bicycle manufacturers would have you believe disc brakes are a necessity for all electric bikes. Of course that is complete and utter nonsense. Two years ago a man was in my shop who had sold over 44,000 electric bikes the previous year and I ask him, "Do you feel disc brakes are necessary for electric bikes?" He replied, "Of course not." If they are not required why do you find them on every electric bike sold in the US? The answer is one of perception. The perception is electric bikes are heavier and faster and therefore require greater stopping power. If that were true then every cyclist over 180 pounds would need to have disc brakes on every bike, not just electric bikes. Also, electric bikes are capable of speeds up to 28mph. In racing we would accelerate up to 45mph in our road and circuit races and 60mph in our descents...while using rim brakes.
If your bike does not have disc brakes that is fine. Just be sure that whatever brake system you have is top drawer and always in top shape. Replace the brake shoes/pads often and make sure they are adjusted correctly. Some brake pads, as they wear, will slowly move closer to the bottom of the tire. Keep on eye on that and make sure the brake shoe never comes into contact with the tire. Since brake shoes are inexpensive, replace them often and replace with the best. Products like "Kool Stop" make fabulous brake products.
Yes, it is possible but I do not recommend that you do so. They make adapters for the front fork and the rear wheel that will allow the use of disc brakes. However, you will also need adaptors for the wheels also in order to attach the disc brake rotor. In the end, you will have a bike with a braking system that has been hobbled together and the performance will not be any better the the one you removed. Personally, I think it best if you prefer a bike with disc brakes then now is the time to purchase a new or used bikes that already has disc brakes and then continue with you conversion to electric.
You three choices of disc brake pads to choose from; Organic, metallic, and semi metallic. All new bikes come with organic (also called resin pads) brake pads. The reason all new bikes come with organic pads is they are the quietest and have great bite on the rotor because they are softer than metallic pads. If you wish to sell the a disc brake equipped bike to the purchasing community then they cannot be squealing loudly on a test ride. Organic pads are quiet. They are made from rubber and fibrous material that is held together with resin. The downside of organic brake pads is they wear out quickly. As far as I am concerned, that is to high a price to pay for quiet brakes.
These pads last a lot longer than organic pads but the downside is they can be quite loud, especially in wet weather. In my opinion, all bikes with disc brakes should use long life metallic brake pads. The organic pads just wear out to quickly. Yes, metallic pads can squeal and screech terribly in wet weather but the answer to that is do not ride in wet weather. It is important to point out the price to pay for quiet brakes is poor braking performance. The reason I say this is I see many bikes with disc brakes in our shop with the resin pads completely gone and the owner is not aware the pads need replacing. They cannot believe the brake pads could be gone so soon.
On this, I would say better than organic but not as good as metallic. I do not believe we have a single pair of semi metallic brake pads in our shop. To use these would amount to "sort of fixing a problem." On the other hand, it might just be exactly what you are looking for. If you have disc brakes on your bike the best advice I could give is learn how they work, how to adjust them, how to replace them, and how to know the difference between quality disc brakes and poorly made disc brakes. They are not that complicated and the knowledge you gain will make riding your bike a much safer experience.