How does one balance a wheel with hub motor?

[MikeFairbanks]

I took my wheel w/ hub motor off (front) to the local bike shop for truing. They did fine, but the wheel is not balanced (neither is the back wheel fully), but the front wheel more so. When I spin it, using the motor (while it's off the ground) there's an up-down wobble. The side-to-side is good now, but there's that up and down wobble.

Should I try to find some lead tape and mess with it? Is it something the LBS can do?

 

[tuxman]

I doubt that it is the rim. An out of round tire shouldn't be that noticeable unless you locked up the brakes down a very long hill.

My guess is the motor is off balance or it has a manufactures defect.

Replace the motor if it's a real issue with a different brand of higher quality. But this may be an inherent issue with all hub motors.

On a scale of 1-3 what do you rate this as?

1 mandatory replacement
2 tinker with it and try to fix but not worth replacement
3 noticeable but not an issue

 

[Rassy]

Mike, when I was playing around with the big hub motors off of a scooter, I found they really made the suspension bounce around when running wheels up, even without the tube and tire. So I just used small weights and trial and error until they ran smoothly. Never tried this on a bicycle wheel, which is normally larger diameter but runs much slower. Those scooter 10" wheels had an outside diamater of 16" and ran close to 30 MPH.

First check to make sure the rim ended up "round". If the spokes weren't installed properly there could be high and low spots on the wheel that might appear as a balance issue.

 

[TylerDurden]

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Bad truing. Good should include radial runout.

 

[MikeFairbanks]

I doubt that it is the rim. An out of round tire shouldn't be that noticeable unless you locked up the brakes down a very long hill.

My guess is the motor is off balance or it has a manufactures defect.

Replace the motor if it's a real issue with a different brand of higher quality. But this may be an inherent issue with all hub motors.

On a scale of 1-3 what do you rate this as?

1 mandatory replacement
2 tinker with it and try to fix but not worth replacement
3 noticeable but not an issue

I'd call it a 3. Definitely no big deal. I'm just fine tuning everything and want silk, so-to-speak.

 

[tuxman]

Bad truing. Good should include radial runout.

OP had it trued, but if this wasn't done, very good point.

 

[Ykick]

Are you running Slime sealant? Large amounts take a while to even out so initial rotation feel out of balance - add in some radial runout and it can approach some type of hammering. I only use a few ounces in my tires and that seems to actually help balance things when it all spins up to speed.

I also use several 9C and Conhis DD's and haven't experienced any evidence they're poorly balanced. I have ran into radial runout issue before.

 

[Dave Sloan]

In the worst case - just put a bike wheel reflector on one of the spokes and slide it up or down until it stops bouncing. Start opposite the valve.

 

[Rafabaca]

Truing normally only deals with the vertical axis, its only the left and right displacement, it sounds like the bike shop only worked on truing it. You need to round your wheel, you do that much the same way as truing but with all the spokes (left and right) on a part of the wheel. if the wheel bumps in on one point do quarter to haft loosen turns on that part, and if it comes out tighten all of those spokes the same way. I'd just go back to that bike shop and complain about how they didn't round the wheels.

 

[MikeFairbanks]

My mistake was going to the wrong bike shop. I just happened to be a few doors down eating and stopped in to talk, then let them take the wheel.

I don't have confidence in them. I should have gone to where I always go: Trek. Those guys are so cool and meticulous (from my experience....I don't want to discount the other shop, but it's just not the place for me). The guys at Trek in my town are super friendly, and there's not a bike snob among them, even though some are really serious riders. They don't care if you're a little girl or an old man. They are very welcoming and accommodating. At the other place I feel like an intruder and an annoying noob.

So I went up to Trek today and they helped me out (free of charge) and I'm in good shape. They also tightened up the brakes, etc., and then I took it out and got it to top out at 28.7 mph on the flats. Not bad.

It's all set for my daily commute (which starts in nine days). The only thing left to do is continue to paint every square inch of it black. I even painted the spokes, the new bell, the brake handles...everything. I don't ride with cars (bike path only) so visibility isn't an issue. Plus I have a headlight and tail light for riding in darker situations, so in the meantime I'm painting it black, top to bottom. The only thing that won't be black is the side of each rim (from the brakes). I did a test patch of paint there, and the brakes tear it right off. Nothing I can do there, but that's okay.

I'm really looking forward to commuting, because it'll be as fast or faster than my car, the weather will be good for a long time, and it's very stress-relieving to ride to and from work.