Bicycle Mechanics - Wobbling/unbalanced Rear End.

With my new Jamis Aurora touring bike I suspect the rear wheel requires balancing of some sort. When on the bike stand I spin the rear tire at a fast rate and it seems to bounce up and down. At first I suspected the rim might be distorted but it seems fine, perhaps it's not perfect and required wheel truing? Or could it be the crappy stock tires they put on? Upon close examintation the tire does seem a little malformed.

It's a very noticeable vibration, if I hold the bike up from the seat post and spin the tire it's very noticeable...almost too much.

Any ideas what may be causing the problem and how I can remedy it?

Thanks

Does the tire jump up and down or does the rim jump?

If it's the tire it's probably not seated right, you may have to deflate it and make sure the bead around the entire tire is on the rim.

If it's the rim you may either have a flat spot from hitting something or the wheel isn't trued.

The lbs you bought it from should be able to fix either problem under warranty if it is new.

Remove and reseat the tube and tire. Some vertical wobble is always there because of the valve.

I've balanced that vertical wobble out with lead tape on one bike. On the road I'm not sure I could tell the difference.

Turn the wheel slowly next to a fixed object with and without the tire to see which is out-of-round.
If the tire is seated properly and the rim is round but the tire is still out-of-round then you may have a defective tire, it's happened to me.

Al

I would definitely suspect a funky tire rather than an out-of-round rim.

If you spin the rear wheel fast of ANY bike in a bike stand, the whole thing will vibrate like crazy. Perfectly normal.

Now, if it vibrates like that on the road, then definitely do the above posted checks.

If you spin the rear wheel fast of ANY bike in a bike stand, the whole thing will vibrate like crazy. Perfectly normal.

Now, if it vibrates like that on the road, then definitely do the above posted checks.

I was wondering if anyone would catch this; nice one, SR.

BTW, your weight on the bike eliminates this when you are riding.

If you spin the rear wheel fast of ANY bike in a bike stand, the whole thing will vibrate like crazy. Perfectly normal.

Now, if it vibrates like that on the road, then definitely do the above posted checks.

On cheap bikes it'll do this yes. Espeically ones with fat tires that don't seat correctly. There's also an important distinction between normal bounce in the stand and bounce because of an improperly seated tire.

If you spin the rear wheel fast of ANY bike in a bike stand, the whole thing will vibrate like crazy.

Not the ones I balanced with lead tape. Spun smooth at any speed. Only took a few grams of tape. But I don't think it made any difference on the road

Not the ones I balanced with lead tape. Spun smooth at any speed. Only took a few grams of tape. But I don't think it made any difference on the road

You can also use split-shot (small fishing sinkers) crimped onto the spokes for this.

(See? I'm anal, too!)

You can also use split-shot (small fishing sinkers) crimped onto the spokes for this.

(See? I'm anal, too!)

You guys ADD weight? Why would you do that? Why?:D

You guys ADD weight? Why would you do that? Why?:D

Yeah! Maybe a better solution is to replace the nipples on the other side of the rim with lighter nipples. ;) Weight weenie savings and satisfy the anal retentive need for perfect balance.

Not the ones I balanced with lead tape. Spun smooth at any speed. Only took a few grams of tape. But I don't think it made any difference on the road

I was going to say, that balacing bicycle wheels is probably overkill from a functional perspective. Even on very fast descents, 50 mph+, I have never had a wheel feel unbalanced. With the low mass of wheels, I think you would have to really get them spinning before you felt any vibration.

I was going to say, that balacing bicycle wheels is probably overkill from a functional perspective. Even on very fast descents, 50 mph+, I have never had a wheel feel unbalanced. With the low mass of wheels, I think you would have to really get them spinning before you felt any vibration.

Agreed (guess this is your day, SR! :)).

My comment about the split shot was kinda in jest although I have seen people do it. I love fast mountain descents (like that last section in the Rosarita-Encinata ride!) and have never noticed a wheel being out of balance.

I don't think there's enough weight variation and/or speed involved for it to matter.