Replacing the Blue Wheel on TSDZ2 Mid Drive Electric Bike

The TSDZ2 Mid Drive Motor lets you turn a regular bike into an electric one, giving your legs a boost of bionic power—the harder you pedal, the more assistance it provides. I think it’s better than the popular BAFANG Mid Drive Motor, which lacks smooth power delivery. I installed the TSDZ2 on my push bike over three years ago and found it great for commuting and shopping. After clocking up 3,300 km, I noticed it was noisier and sometimes took a couple of pedal strokes to engage. I’d read that some users had to replace the “blue wheel,” so I figured that was the issue and ordered one online. When it arrived, it sat on my desk for four weeks because I was nervous about taking the motor apart—what if I messed it up and it stopped working? Having never done anything like it before, I was hesitant, but eventually, fed up with public transport, I decided to face my fears and give it a shot. Nothing ventured, nothing gained.

Replacement gear wheel

I flipped the bike upside down to make the motor easier to work on. I grabbed a plastic chair to sit on, not knowing how long the job would take, and figured I might as well be comfortable. I may have also brought out a cold beverage, but I can’t say for sure.

I had hoped I wouldn’t need to remove the pedal crank, but soon realized there were a couple of screws that weren’t accessible with the crank in place. A special crank removing tool was used to pry the crank arm off. Then the crank nut also required a special tool to remove it. Once removed I was able to remove the screws mentioned above and the screws holding on the engine cover.

With the cover off, I began disconnecting some wires attached to the motor. One wire clip needed to be disconnected and 3 thicker wires unscrewed from there terminals. Take note of which wire goes where, to assist when reassembling. Luckily, I had found a YouTube video of someone who had previously replaced the blue wheel, and I’d recommend watching it for a bit of encouragement before attempting the task yourself.

With the wires removed, you can slide out the motor armature. Fortunately, on my bike, it came off easily, revealing the 'blue wheel,' which also slid off without any trouble.

Examining the removed wheel, the external gears looked fine, but on closer inspection, I noticed some inner roller bearings. These act as a clutch, allowing the motor to freewheel if needed and engage when the pedal crank is rotated. The roller bearings, however, were no longer engaging.

The blue wheel was replaced with the one I had purchased. Interestingly, it was a white wheel, but the seller assured me it was identical to the blue one except for the color. I applied a bit of silicone grease to the new gear and slid it onto the gear shaft. Then the motor armature was refitted, and the wires reconnected.

I fitted the cover, ensuring the seal was clean, and secured it with the screws. Then I reattached the pedal crank and crank nut, adding a drop of thread lock to the nut’s threads to keep it secure. When I powered on the bike, nothing happened at first, and I felt a brief moment of worry—until I realized the battery switch was off. Once switched on, the motor panel lit up, and I took the bike for a test ride to the local hardware store. The motor ran smoothly, and the crank engaged effortlessly—a successful blue wheel replacement.