The bearings in my BionX hub motor began to die at around 6500km, and now completely worn out at around 9500km. The wheel had a lot of play, and power consumption went up by about 30-40%. Surprisingly, I couldn’t find a lot of info on the web.
As always, this is not a complete guide, but I try to point out those parts of the procedure that were not straight forward to me. If you’ve done it yourself and have something to contribute, please do so using the comments function.
Tools / Parts needed:
- Bearings: SS 6003 2RS Stainless Steel 17 x 35 x 10 mm
- Strain Gauge: Mine survived
- M8 bolts + nuts or similar, as tool (see below)
- Freewheel removal tool
- Spoke key
- Hydraulic press
- Bearing puller
- Straight puller
I didn’t do it in the same order as I recommend here, but I think this is the best order to do it.
First step – Take the hub apart:
Remove the Freewheel
Remove the torque blocker (pressed onto the axle, brake side). Mine was just cone-shaped, but the newer ones seem to have a notch, so don’t try to rotate it, use a straight puller to remove it.
Remove the spokes on the brake side, this should suffice / I’ve left the drive side spokes in place. Mark the hub, so that you know how to align the halves when reassembling. I’ve used 9 M8 bolts and nuts to actually press on the inner walls of the hub shells. It was surprisingly easy to get it apart by doing so.
Second Step – Remove the bearings:
The bearing on the brake side covers the strain gauge, which measures torque applied through the pedals. I have read, that this will usually break during disassemble – luckily mine didnt. The bearing came off the axle / stayed in the hub shell. Getting it out of the shell was a job for a hammer + some alloy tubing.
To remove the drive side from the inner part of the motor, we have used a hydraulic press (sorry I somehow missed to take pictures). So this wasn’t easy, and I needed help from someone with the right tools. It eventually came out, and the bearing stayed on the axle.
Removing that bearing is quite difficult, as you don’t have much room below it, to actually use a puller tool. Luckily the mechanic had something like this (with barely enough room to house the cables while pulling):
Third Step – Reassembly:
With that bearing out of the way, it was time to clean the axles, place the new bearings onto the shaft. Add new silicone to protect the strain gauge, as well as replacing any heat shrink that has been removed. I then continued with adding the brake / magnetic side, but I’m not sure if it wouldn’t be easier to first push the axle onto the brake side, as there’s no magnetic involved.
Anyway, since I was back at my workshop, I didn’t have the hydraulic press available, and I’ve used my bench vice to gently press the hub halves together (lots of rotating / small steps were involved).
Add spokes, true the wheel go for a ride.
It’s running smooth again, so it was worth it. It took me about 5 hours to do it, If I’ve had the right tools from the beginning, it would have been much less. So if you want to do this, be sure that you have access to the right tools.