Rear brushed motor wheel - Centering rim

[RedDwarfIV]

I recently purchased a 26" brushed motor wheel off eBay. I have everything I need (battery, controller, wheel) and I've tested it and it runs great. One problem.

I can't fit it to the bike.

The issue is twofold, but the first part I don't need help with because I already know how to get that fixed. The second part is that the wheel rim is centred in the middle of the motor, not in the middle of the motor plus sprockets. As such, with a tyre fitted the wheel just rubs heavily along one of the back forks and if I were to fit it, it wouldn't go in a straight line since it wouldn't be lined up with the rest of the bike. It's not dished at all.

I have taken it to an electric bike shop and they told me the flanges that the spokes attach to were too far from the edge of the motor, meaning that if I tried to move the rim over, it would be past the motor flange and I'd end up with a wobbly wheel.

Any ideas?

For visual reference.

 

[Alan Quay]

I don't understand the problem. Why not just dish it?

Usually, with a combination of dishing, and a 5mm stretch of the frame, with an anti rotation washer on the inside, non drive side it should fit.


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[Nealh]

It needs dishing which you can do your self fairly easily if you have the right spoke tool. As Alan has said on the side that is tight ( non drive side) place
a AR washer on the inside of the drop out. Turn the bike upside down and with the wheel tightened in place start to dish the wheel, undo each spoke on (non drive side) 1/2 a turn or 1 whole turn starting at the valve, then on the drive side tighten each spoke the same amount. One tip is every time you adjust a spoke dab a bit of tippex on it so you don't loose where you are at or use a piece of masking tape to mark the last spoke you loosened or tightend depending on which side you are working, with each spoke adjustment you will see how many mm the wheel moves over so will give you an idea of how much more adjustment is needed. As long as you are methodical the wheel should remain true, once you have the confidence to do this it doesn't take very long to do.

 

[RedDwarfIV]

Okay, I'll try that. The problem was that I was told (and everything I could find on the Internet backs this up) that you're not supposed to have one side's spokes go past 90* or you will have an unstable wheel.

 

[Nealh]

The last diagram (problem) is quite severe and if your wheel looked like that then it would be unsafe, however for it to look like that you would need new longer spokes on the non drive side. All though a pain as weel as the AR washer some thin shim washers may also help, idealy the final dishing should be like the middle diagram. Set time a side to do the job an don't be rushed or interrupted.

 

[RedDwarfIV]

The last diagram (problem) is quite severe and if your wheel looked like that then it would be unsafe

Oh, I just wanted to make sure the diagram was obvious. It wouldn't be that bad, although I agree that even to dish the rim now I'd need longer spokes.

I have had an idea though.

See the screws for holding the motor together? I could use those as a mounting point for a machined annulus that could act as a flange. That would allow me to then attach the spokes to that instead of the inside flange on the motor.