Magic Pie 5 Vector EXTREMELY Hard to spin

[Leftiebiker]

   I don't have the motor connected yet - just finished installing it on the dropout. It is so hard to turn the thing, though, that I'm wondering if I have a defective motor. I can turn it with one hand, but only with difficulty. It feels as though it has invisible rim brakes gripping it. I eliminated the fender and the brake caliper as suspects, leaving only the motor itself. Having spent $100 getting the wheel trued, spokes adjusted (they were literally loose and rattling from the factory) and tire mounted, I'm extremely unhappy at the prospect of having to return the thing. Am I mistaken? Is this normal for a new MP5?

[Bikemad]

Hi LB

Having already eliminated the brake caliper and the fender, the three most likely remaining causes of the wheel being "EXTREMELY Hard to spin" when fitted to the bike are:

 1) The brake disc retaining bolts are too long and the ends of them are binding against the controller.
 2) The freewheel is binding against the inside of the dropout, or possibly binding against the outer circumference of the inner axle washer.
 3) The tyre itself is rubbing against either the inside of the chainstay or seatstay part of the frame.

Try undoing the disc mounting bolts a couple of turns and then see if the wheel turns easier.
If shorter bolts are not available, try adding washers under the head of the bolts so they can't thread in far enough to touch against the controller.

This is the result of using a Magic Pie when disc mounting bolts have been used that are too long:



If the disc bolts are not responsible for the binding problem, try slacking off the right hand axle nut and see if the binding is reduced.

If the freewheel body is touching the frame, you will need to fit an additional inner spacer washer.
In some cases, you may also have to reduce the outer diameter of the spacer washers using a file or angle grinder etc. to ensure they fit inside the freewheel with touching it:





If it's the tyre rubbing against the frame, simply slacken the axle nuts and realign the wheel alignment until the tyre clears the frame.

If the wheel had been that hard to spin before it was fitted to the bike, it should have been very obvious when the wheel was trued and the spokes adjusted.

Alan
 

[Leftiebiker]

   Thanks for the detailed reply. The guy who did the work on the wheel isn't very familiar with e-bikes.

The tire is not binding anywhere.

The freewheel spins freely backwards, but I'll check the washers. It isn't touching the frame.

I used standard brake disk bolts - 10mm, IIRC. Do they need to be shorter?

[Leftiebiker]

   Well, it was indeed the brake rotor screws. Why on Earth isn't there a BIG sticker on the motor, saying to either use washers as spacers, or use shorter than normal screws? I really, really hope that the motor isn't screwed up. What would be the signs if it were...?

[Bikemad]

I used standard brake disk bolts - 10mm, IIRC. Do they need to be shorter?

It looks like you've already discovered the answer to your own question - the disc bolts do need to be shorter than 10mm if you don't want to add washers.

I really, really hope that the motor isn't screwed up. What would be the signs if it were...?

As you have not yet used the bike, it is unlikely to have any detrimental effect upon the operation of the motor.
The surface of the controller's cooling fins may have sustained some cosmetic damage, but this is probably not going to be obvious without removing the cooling fan/disc mount assembly.

Fortunately, adding some washers under the heads of the disc mounting bolts should be a relatively simple fix.

Alan
 

[Leftiebiker]

   Done - I used one flat and one lock washer on each, just to make sure they stay backed off enough. Now, why, why, WHY isn't this noted on the motor? It's bad enough that there are no written instructions for it. If you can't use standard disc brake screws without spacers, that really should be the subject of a big, red warning label on the motor.