what kind of tire are you using? what kind of valve extender?

sometimes this problem is caused by using a (relatively) heavy non-zipp valve extender. the zipp extenders are very light and work great IF you set them up right.

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Where would you want to swim ?

If you bought it new I'd take it back to the shop for a new one. I assume you're talking about the radial true of the wheel, which shouldn't be more than 1-2mm. If it's radially true but bounces because of the carbon being thicker in one area than another, I'd want a new wheel.

Either way, it should not do this, and I'd want a replacement. Did it bounce like this when you first got it?

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"Lemond is cycling's version of Rev Jessie Jackson." -johnnyperu 5/18/07
"Just because I suck doesn't mean my bike has to" -rickn 9/2/08

I have a Conti Competition tubular with the Zipp valve stem.

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Racing Ironman for Athletes in Tandem...http://www.firstgiving.com/...manworldchampionship

Are you using a tire on it, when you spin the disc?

"Are you using a tire on it, when you spin the disc?"


Yes, see above post. New Conti competition tubular with Zipp extension.

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Racing Ironman for Athletes in Tandem...http://www.firstgiving.com/...manworldchampionship

<Either way, it should not do this, and I'd want a replacement. Did it bounce like this when you first got it? >

I've only ridden the wheel once in one short race (oly). I noticed the problem after the race, but I'm sure it was there before it.

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Racing Ironman for Athletes in Tandem...http://www.firstgiving.com/...manworldchampionship

I think I know what you mean. If the rim is true, and nothing wrong with the tire and you have the back of the bike bouncing (shaking) on the stand it is common. It is usually the freewheel/hub and unnoticable by eye. JKust take a look at the line where the rim and brakepads are alligned. if they are perfectly alligned through out the rim while you pedal on the stand don't worry. If you notice this while you are riding, then you start to worry.

Your one ride could have knocked it out radially since it was the first ride.

Tire needs to come off and wheel needs to be checked in a truing stand for radial limits.

Just because it is brand new all wheels could need some checking,(spoke tension,dish,lateral,radial)

<I think I know what you mean. If the rim is true, and nothing wrong with the tire and you have the back of the bike bouncing (shaking) on the stand it is common. It is usually the freewheel/hub and unnoticable by eye. JKust take a look at the line where the rim and brakepads are alligned. if they are perfectly alligned through out the rim while you pedal on the stand don't worry. If you notice this while you are riding, then you start to worry. >

Yes, the wheel is perfectly true...no lateral movement when watching contact with brake pads. I was hoping somebody would say this, as I'm leaving town next week and just don't have time to mess with shipping the wheel before Kona. I do have an alternative wheel I could use though. I don't notice any problem at all while riding.

As a side note, I noticed the same thing happen with the Hed3's I used to ride (they were borrowed from my cycling team, so not focused on fixing the problem) and rode them anyway without any noticeable problems.

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Racing Ironman for Athletes in Tandem...http://www.firstgiving.com/...manworldchampionship

Valves and Valve extedners weigh a lot. If you're worried, take the tire/tube off and spin it in your bike. If it is still really wobbly your wheel is screwed. If not, it's just the extra weight of your tire/tube.

90% chance is that it's the weight of the valve/valve extender and you're worrying because the big race is coming up!

'nuff said, have a good race in Kona.

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My training

you can check the radial true of the wheel without removing the tire-just spin it slowly and look for up/down movement comparing the top of the rim to the brake pad. That said, it most likely the tire--most tubulars are lumpy, and spinning it in the stand really demonstrates that fact.

I've tested some really lumpy tires on rollers, and some of the fastest tires have been very lumpy. I'd expect those results to carry over to the road. I don't know how 'scientific' you consider that to be, but there you go...

<you can check the radial true of the wheel without removing the tire-just spin it slowly and look for up/down movement comparing the top of the rim to the brake pad. That said, it most likely the tire--most tubulars are lumpy, and spinning it in the stand really demonstrates that fact.
I've tested some really lumpy tires on rollers, and some of the fastest tires have been very lumpy. I'd expect those results to carry over to the road. I don't know how 'scientific' you consider that to be, but there you go... >

Just spun the wheel again and the rim looks nice and true, both up and down and side to side. The tire, on the other hand, has an up and down component (i.e. it's lumpy) and it's definitely weighted toward the valve stem.

Thanks for the help everyone...looks like it's the tire and not the wheel. Glad the lumpy tires are fast on rollers because I will probably ride the lumpy tire (I'm too broke to buy a new one...especially because I'll bet the new one will be lumpy too). My last question is should I try to add weight opposite the valve stem to balance it a bit???

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Racing Ironman for Athletes in Tandem...http://www.firstgiving.com/...manworldchampionship

I have exact the same with my Zipp 404 clincher.

It bounces when the wheel spins fast in the air. It's not due to a wobble.

How sure are you that you don't have it in your front wheel? Can you spin it as fast as you do with your rear wheel?

But I don't have problems with it when I sit on my bike. The imbalance/bouncing is due to a subtle change in weight which is nothing when you sit on your bike.

no, don't worry about it. the only suggestion is that if you're using a computer magnet, put it opposite the valve stem.

<no, don't worry about it. the only suggestion is that if you're using a computer magnet, put it opposite the valve stem.>

Thanks...will do. I'll probably take off the valve extender and put it with the spare as well.

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Racing Ironman for Athletes in Tandem...http://www.firstgiving.com/...manworldchampionship

Well balance is very important! evry wheel have to be balanced ,a good balance always is on 3 spots ,if you do 2 spots you always have a disbalance

I understand that its difficult to do it by hand but can be done ,normaly we do dynamic balance wheels .

Imbalance when riding at high speed of a moutain can lead to accidents and even death!.
You would not be the first one who have a accident like this , even disbalance in wheels can lead to totaly out of control of the bike going over the so called eigenvalue of the bike.

so yes balance your wheels!!

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<Might I suggest updating your original post then.>

Good point...done.
I love my Zipps : ).

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Racing Ironman for Athletes in Tandem...http://www.firstgiving.com/...manworldchampionship