I was about to post about how I wanted to get a rear-wheel kit but I wasn't sure it would work out, since I have a bike made for a standard-sized rear wheel. But I received a reply to my question sent to philip from goldenmotor. He said they have fixed the issue with the rear wheel being too wide for standard bicycles.
Hi Julian,
We have already resolved this issue in our factory. The new rear wheel hub motor spacing become 128mm which suitable for most rear wheel bike dropout.
Thanks,
Philip Yao
I'm excited about getting my rear-wheel-drive electric bike up and running!
I believe my rear dropout spacing is 135mm, but I know from experience that a narrower hub can fit a steel frame with that dropout spacing. You can use washers to take up the extra space. Or just use the torque from the axle nuts to push the dropouts together (no permanent bending of the frame required) although it would be a pain to have do so every time this if you frequently remove/reinstall the wheel.
Here's why I think a rear-wheel motor would be a good idea for me:
I'm figuring if I ride in conditions of questionable traction (Most winters, I use my bike to get to work even when there's snow on the roads) I will want the powered wheel to be the one with more weight on it. Especially when going up a steep hill. Since I expect the motor to be stronger than pedal power I suspect that if it is on the front wheel, it will tend to lose traction going uphill. (and I'd rather lose traction on the rear wheel, since I have had good success recovering from a slipping rear wheel but not from a slipping front wheel.) Not riding in the snow is not such a good option for me, because I can't tell my employer that I only go to work if there is no snow on the roads.
I don't think I will mind having so much placed in the rear of my bike, partly because, say I am braking while going downhill, then a lot of the rider's weight is placed over the front wheel but with the motor and battery weight toward the rear, I will be able to use the traction from both tires to brake a bit better than I could with the weight further forward.