The first thing to do with a rear hub motor eBike conversion is to prepare the motor and frame for the first test fit. As shown in the video, the initial preparation includes:
- Tighten disk brake rotor mounting screws
- Install freewheel
- Check width between dropouts, 135mm minimum
- Check dropout for exact width of 10mm
This install doesn’t cover disk brake installation; Leah’s eBike uses rim brakes. For a rim brake install, all that is required is to make sure the rotor mounting screws are snug.
Make sure to apply anti-sieze or other lube to the threads before installing. This will make it easier to remove later as needed.
Make sure the threads are lined up before threading on. The freewheel should spin on without resistance. If it binds, stop, back off and try again. Otherwise, the threads will be damaged.
Check width between dropouts, 135mm minimum
I’m using an E-BikeKit rear hub motor. It’s OLD (Over Locknut Dimension) is 135mm without spacers or washers. If the inner washer is used, the OLD increases to about 140mm.
For the first test fit, 135mm width between dropouts is enough. If the width between the dropouts is less than 135mm, the stays will need to be spread apart. The width on Leah’s bike turned out to be 136mm so I don’t need to spread the stays for this step.
Since I’m going to be using the the inner washers on the final install, the width between the dropouts needs to be 140mm. I’ll have to widen the stays later. I’ll show how I do this in the next video. For now, I just want to get the hub motor installed to check for other clearances and centering as well as prepare the dropouts.
Check dropout for exact width of 10mm
The hub motor axle keyway is a full 10mm. Most bikes have dropouts to accommodate a 10mm axle but could measure slightly less because of paint. Some careful filing or sanding might be necessary to make the dropout width the full 10mm. The hub motor axle is going to need the full 10mm before it will slide into the dropouts.
My dropouts had a thick coat of paint which made the dropout width slightly less. I had to carefully file the paint off to get it to 10mm.
A general note about filing and sanding: Take it easy and take your time. It’s a lot easier to remove metal than it is to replace it. You can ruin your bike by removing too much metal or leaving jagged edges. Make sure to file a little, test fit, and then file a little more as needed. Make it smooth, clean looking, and precise. Large gaps will make the fit loose. Jagged edges are opportunities for cracks to form.
The next video will cover dropout preparation, checking freewheel clearance, and centering between stays.
Stay tuned for more details as this project proceeds.