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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 07-28-07, 03:54 PM   #1
xfimpg
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What would you do with this problem?

Hey everyone,

Here's my setup:
- Pinarello Angliru 2007
- Tiagra 2007 everywhere
- wheelset is OEM and brand is M.O.S.T. (huh??); i think it's Taiwaneese, I think, not sure.
- tires are brand new and Ultra Gatorskins
- bike has only 1000 miles on it.

I have problem with my rear wheel. It wobbles around 20mph and up - but disappears around 35mpg+ and "feels" like I'm riding on low air pressure - but the pressure is correct - 120psi.

I'm going nuts here. This is what has been done so far:

- had the rear wheel "trued" by an LBS and rechecked by another cause the problem was obviously still there.
- the 2nd LBS found the cassette loose in the back and retightened.

Now it rides better but the wobbling is still there and i still have that darn soft rear tire feeling.
Please don't tell me i need to see a psych.

Any advice you can give me would be greatly, greatly appreciated.
Mike
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Old 07-28-07, 07:34 PM   #2
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If the wheel has been professionally trued, that should not be the problem. You can easily check this yourself; just put a finger very close to the rim and give 'er a spin. There should be no more than 1mm of side-to-side play. Likewise check for roundness.

Possible things to check might include a badly-manufactured tire. Does the wheel seem unbalanced? If spun, it should naturally end up with the stem side down. If it doesn't, there may be a "thick spot" or other defect.
Hub-bearing failure? Does the wheel spin freely and without any crunching side-to-side play?
Frame/wheel alignment problems will normally just cause pulling or bad tracking; if things were really "out" it might cause a wobble sensation.

It sounds like loose spokes to me; but if the wheel has been properly trued that shouldn't be the problem.
Wouldn't hurt to give them all a little tap with a wrench and see if you get a similar tone from each.
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Old 07-28-07, 07:34 PM   #3
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Get up to 35mph often, do you?

Seriously, isolate the problem by trying another wheel, another tire, etc. I've never seen a wheel present that kind of problem. Frames, yes. It could happen, so if you are certain it IS the wheel, make sure it's dished properly, the tire is not damaged somehow, and there isn't the OEM reflector still on it. Something that would cause it to be unbalanced at those speeds.
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Old 07-28-07, 08:30 PM   #4
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Quote:
Originally Posted by neilG View Post
Get up to 35mph often, do you?

Seriously, isolate the problem by trying another wheel, another tire, etc. I've never seen a wheel present that kind of problem. Frames, yes. It could happen, so if you are certain it IS the wheel, make sure it's dished properly, the tire is not damaged somehow, and there isn't the OEM reflector still on it. Something that would cause it to be unbalanced at those speeds.
On descents I get to 35mph and higher, should've clarified that.

Thanks guys for the advice, I'll approach it your way and let you know how it works out.
Mike
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Old 07-29-07, 12:56 PM   #5
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Hijack, sorta:

I'm getting a wobble in the front wheel (Shimano WH-R540 (pdf)) when I take my hands off the bars at descent speed. Hub and headset are both solid. Even with the wheel wobbling there's no appreciable vibration at the bars. I'm thinking there's a resonance between the rim/tire and the axle.

xfimpg - how many spokes in your wheel?
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Old 07-29-07, 01:10 PM   #6
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Quote:
Originally Posted by DMF View Post
Hijack, sorta:

I'm getting a wobble in the front wheel (Shimano WH-R540 (pdf)) when I take my hands off the bars at descent speed. Hub and headset are both solid. Even with the wheel wobbling there's no appreciable vibration at the bars. I'm thinking there's a resonance between the rim/tire and the axle.

xfimpg - how many spokes in your wheel?
Stupid question, but is the QR clamped down correctly? I don't buy the resonance theory.
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Old 07-29-07, 01:14 PM   #7
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Quote:
Originally Posted by Bikewer View Post
If spun, it should naturally end up with the stem side down.
Don't bet on it.

I used to think that too until I started installing a lot of bike computers. My practice was to let the front wheel find it's own resting place thinking that the lightest point would be the best place to install the wheel magnet. Typically the wheel will stop with the valve stem on top.

Metal is taken out of the rim to make the valve stem hole and steel pins will have been inserted into the extrusion at the joint opposite the valve stem.
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Old 07-29-07, 01:26 PM   #8
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Yes QR is/was fine. Just to be sure I had the SAG mechanic check all of the above (headset, hub, QR) and he didn't see anything wrong either.


>> Typically the wheel will stop with the valve stem on top.
+1
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Old 07-29-07, 01:31 PM   #9
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Quote:
Originally Posted by DMF View Post
Hijack, sorta:

I'm getting a wobble in the front wheel (Shimano WH-R540 (pdf)) when I take my hands off the bars at descent speed. Hub and headset are both solid. Even with the wheel wobbling there's no appreciable vibration at the bars. I'm thinking there's a resonance between the rim/tire and the axle.
Flip your front wheel and see if the problem persists. Sometimes, a tire can cause this.
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Old 07-29-07, 02:02 PM   #10
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Good idea. I'll also try a different wheel (same wheel, different tire).

Another suggestion was crosswind. Not an aero wheel, but the section is fairly deep.
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Old 07-29-07, 03:17 PM   #11
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Quote:
Originally Posted by DMF View Post
Hijack, sorta:

I'm getting a wobble in the front wheel (Shimano WH-R540 (pdf)) when I take my hands off the bars at descent speed. Hub and headset are both solid. Even with the wheel wobbling there's no appreciable vibration at the bars. I'm thinking there's a resonance between the rim/tire and the axle.

xfimpg - how many spokes in your wheel?
Hey DMF, no hijack, no worries.
20 spokes in front, 22 in the rear.
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