Converting Your Bike Is Actually Easier Than You Think
by Brent Robinson on Sep 01, 2023
You’re still thinking about adding a middrive motor to your bike but you’ve heard it is a complicated process. It can be. With the right preparation, you can do this.
Let’s go through the basic process, some of the gotchas you might experience, and some ways to simplify your upgrade.
Take Off the Old Parts
- To do the install, you’ll need to remove a few things first. The motor goes on the bottom bracket housing. This means the chainring, bottom bracket, front derailleur and front gear shifter have to go.
- Gotcha #1 - special tools. You will need a crank puller, a chain breaker, and a bottom bracket removal tool for your specific bottom bracket.
- All three are relatively cheap, you can buy from your local bike shop (always support your local bike shops!), or even borrow it from them.
- Sometimes, you can even ask them to do it for you for a minimal or even no cost.
Install the Motor
- The motor has a spindle that slips into the bottom bracket housing and some brackets and bolts to lock it down. There is a special tool needed to tighten the lock nut but it comes with the kit.
- Gotcha #2 - frame welds - The bottom bracket housing is where the tubes of the bike come together and are welded. Sometimes those welds on the inside will come just inside the housing. If this happens, you may have to file that down. A Dremel is the best way to do this.
- Gotcha #3 - Cables in the Way - Most shift and brake cables will go under the bottom bracket. There is just enough space between the motor and the housing for the cables to fit. Sometimes there isn’t enough clearance to slide the motor over. Just taking the four bolts off the motor housing usually gives you the clearance to slide the motor over the cables. Other situations might require you reroute the cables above the housing.
Mount the Battery
- Rack mount batteries are the easiest because they go on a rear rack that’s made for holding the battery. Downtube batteries use the two bolts for the waterbottle cage to mount on the downtube.
- Gotcha #4 - make sure the battery fits - You have to be sure the size of battery you order will fit inside your bicycle frame. Measure your frame before you buy.
Add the sensors
- All kits have a speed sensor that mounts on the rear left chainstay with two zip ties.
- The Bafang kit has additional brake and shift sensors that tell the controller to cut off power when you brake or shift.
- Gotcha #5 - combo shifters - if your shifter and brake levels are the kind that are connected together, since you won’t be using the front gear shifter anymore, you’ll need to replace the combo shifters on the left grip with a single brake lever.
- You’ll need to have a separate brake lever to replace the combo assembly.
- For mechanical brakes on a Bafang kit, there is an integrated lever and sensor available.
- For hydraulic brakes on a Bafang, you’ll need to 1) buy a separate brake lever and 2) use the Bafang mounted brake sensors.
- The Tongsheng torque sensing motor has these sensors built in.
Add the display
- Both kits have different displays with different mounting options. All go somewhere on the handlebar either in the center or on the left grip next to the brake lever.
Route the wires
- The display and sensor wires all need to be routed back to the motor at the center of the bike. This is a little bit of science, alchemy and art. You’re going to use zip ties to get the wires tucked away so it looks good. Use the existing cables for routing and attaching.
- Gotcha #6 - crimped wires - If you end up with excess wire, you’ll have to find a way to wrap it up neatly and tuck it behind the seat post, between the motor and the chainstays, or along the cables. However you choose to hide your wires, do not bend them into tight loops. Overbending can crimp or break the wires inside and cause a short.
Converting your bike to an eBike can be a straightforward task with the right preparation and tools. Embrace this DIY project to enjoy a cost-effective entry into the eBiking world, while giving your old bike a modern twist.