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Discussion Starter · #1 ·
So my new Reynolds Assault wheels are great wheels. Braking is solid and predictable and the wheel flex is non-existent. The only issue I am annoyed by is the wheels at 35mph+ speeds. The wheels at high speeds start to feel like they are out of round or out of balance if that makes sense. The wheels have a surging feeling. That is the best way I can describe it. Here in New Mexico, there are lots of steep descents that are pretty short so I get it often. It is un-nerving as it increases as speed increases to 40mph. I don't feel out of control, but in a cross wind it could get exciting. I un-mounted the tires and put the wheels in my truing stand. Both wheels are round within a millimeter, and when spun don't have a noticeable unbalanced spot. The wheel simply comes to a stop at different places each time. Could the lightweight rim be that affected by the 60mm valve stem weight that it un-balances it at high speeds? If it does, I am guessing a spoke magnet opposite the valve stem might work. Obviously with a mounted tire in the truing stand, the valve stem always ends up at the bottom, which you would expect in a balanced wheel.
 

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For a start the valve stem would come to a stop at a 'different' spot each time you spun the wheel if it was balanced properly, but don't get worried about this it matters
very little on a bicycle wheel.
The things I would check are tyre pressure (are you pumping them up to much ?)
Then check the hubs for any lateral play or rough bearings (I would hope not on new wheels but you never know)
One last thing it could be you, maybe you are over tensing yourself when going down
hills fast.
 

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Have you ever driven a car with an unbalanced tire? Does your bike feel the same way? Maybe riding a motorcycle with an unbalanced wheel is a better analogy; 4 wheel vehicles are of course more stable than 2 wheels.

Do you think the feeling at >35 MPH is in one wheel or both? One wheel would point to it being unbalanced. At 35 mph the wheels are spinning at close to 450 rpm; I doubt you can spin them that fast on a truing stand to replicate the effect you are feeling on the road. If the wheel is unbalanced the fix is (as you say) putting a counter weight on it (just like they do with car wheels.) Put the spoke magnet opposite where you think the heavy spot might be, close to the hub. Ride it and if the problem is not solved move the magnet further out. Repeat until you get the ride you are looking for. You might need more than one magnet (hope you are not a weight weenie.)

If a wheel is not unbalanced my second guess is high speed wobble. You can Google this to see all the different theories on what could cause it, but one solution that seems to work in many cases is hold your thigh against the top tube when the bike starts to feel unstable. Adjust pressure against the top tube until you find the point where you are providing the correct amount of damping to absorb the wobble.
 

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There are a ton of unbalanced wheels on the road and a lot of people using big valve stems on light wheels......but very few people reporting what you are.
I'm of little help here but I think you're probably backing up the wrong tree, so to speak, by looking into wheel balance as a cause. The sensation you describe would be very common is wheel unbalance caused it and it isn't.
 

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Discussion Starter · #5 ·
I went through everything today one more time with the wheel and noticed that even though the Reynolds skewer felt tight, I could still twist it when the lever was tight. Maybe a skewer that isn't tight enough. Next ride will have a different set of skewers for trouble shooting step one. Reynolds suggested a loose headset, though I don't think that is the case because it doesn't do it with other wheelsets, but that is definitely an easy fix. Will try those two things out first to see where I get.
 

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Could the lightweight rim be that affected by the 60mm valve stem weight that it un-balances it at high speeds?
Absolutely not. In order for that to be the case the force of the spinning valve stem (or any other out-of-balance weight) would have to actually compress the tire. Since you're already preloading the tire at 80-100 lbs. it is inconceivable that the weight of an out-of-balance wheel could do anything.

The analogy with car tires and motorcycle tires is not applicable - both are suspended locally whereas the bike wheel is suspended via your body. Also the car tire and motorcycle tire are run at much lower pressure and can therefore compress due to the imbalance forces. Balancing bicycle wheels is essentially a parlor trick to impress the uninformed.
 

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Discussion Starter · #7 ·
Kerry, do you have any ideas where it could be coming from? I checked the endcaps on the sealed bearings and they were tight. No other bearing adjustment I could see. Loose skewer feasible?
 

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Kerry, do you have any ideas where it could be coming from? I checked the endcaps on the sealed bearings and they were tight. No other bearing adjustment I could see. Loose skewer feasible?
Loose skewer seems unlikely. Could it possibly be the bike in a wobble rather than the wheels "surging"? I have never experienced this and really have no ideas. Any possibility that it is more a "feeling" than actual speed changes?
 

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Did you try changing tires? I have a Specialized Aramdillo that spins funny at high speed. It always goes away when I change the tire but it always ends up back on another wheel.
 

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“In order for that to be the case the force of the spinning valve stem (or any other out-of-balance weight) would have to actually compress the tire.”

Well, I don’t know. When they check/fix an unbalanced car tire they spin it horizontally, with no load compressing the tire. I believe they use a light (timing light? laser?) to see the wobble in the wheel and where to put the counter weight. So apparently at least one effect of the wheel/tire being unbalanced can be observed without a load and without the tire compressing.

Here is explanation of wheel unbalance that does mention tire compression:
Tire balance - Wikipedia, the free encyclopedia
“…wheel and axle assembly are a rigid rotor to which the engine and brakes apply a torque vector aligned with the axle. If that torque vector is not aligned with the principal axis of the moment of inertia, the resultant angular acceleration will be in a different direction from the applied torque. Whenever a rotor is forced to rotate about an axis that is not a principal axis, an external torque is needed. This is not a torque about the rotation axis (as in a driving or braking torque), but is a torque perpendicular to that direction. If the rotor is suspended by bearings, this torque is created by reaction forces in the bearings (acting perpendicular to the shaft). These reaction forces turn with the shaft as the rotor turns, at every point producing exactly the torque needed to keep the wheel rotating about the non-principal axis. These reaction forces can excite the structure to which they are attached. In the case of a car, the suspension elements can vibrate giving an uncomfortable feel to the car occupants. In practical terms, the wheel will wobble.”

“Balancing bicycle wheels is essentially a parlor trick to impress the uninformed.”

That could very well be true. I’m going to try putting a large mass on the rim of my front wheel next time I ride to try to be less uninformed.
 

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Auto tires shake horizontally. They can shake vertically as well, but that causes irregular wear. The shake you feel is horizontal. A tire and rim can be 50lb on a car, and the imbalance can be a few inches off center. At speed, this can cause quite a bit of weight being swung off center.

Bike tires and rims arent wide or heavy enough to cause a horizontal shake.
 

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“In order for that to be the case the force of the spinning valve stem (or any other out-of-balance weight) would have to actually compress the tire.”

Well, I don’t know.
Clearly this is the case. In order for the rider to feel a vibration then the weight imbalance would have to cause the tire to compress. Simple as that. There can be no up and down motion unless the tire compresses. And at 6-7 bar pressure, the weight of a valve stem or rim seam is not going to make this happen.
 

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If a tighter skewer doesn't fix it I'd check to see if you have a wonky tire. Uneven wear or a slight imperfection might cause a problem like yours.
Even new ones are a little off sometimes.
 

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Clearly this is the case. In order for the rider to feel a vibration then the weight imbalance would have to cause the tire to compress. Simple as that. There can be no up and down motion unless the tire compresses. And at 6-7 bar pressure, the weight of a valve stem or rim seam is not going to make this happen.
A 10g valve stem on a 700x23 tire at 40mph exerts a centrifugal force of approximately 1 lbf as it rotates 8.5 times per second.

It's amusing how reliably you assert that small differences are meaningless.
 

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Is the "surging" a feeling or a sound?

So my new Reynolds Assault wheels are great wheels. Braking is solid and predictable and the wheel flex is non-existent. The only issue I am annoyed by is the wheels at 35mph+ speeds. The wheels at high speeds start to feel like they are out of round or out of balance if that makes sense. The wheels have a surging feeling. That is the best way I can describe it. Here in New Mexico, there are lots of steep descents that are pretty short so I get it often. It is un-nerving as it increases as speed increases to 40mph. I don't feel out of control, but in a cross wind it could get exciting. I un-mounted the tires and put the wheels in my truing stand. Both wheels are round within a millimeter, and when spun don't have a noticeable unbalanced spot. The wheel simply comes to a stop at different places each time. Could the lightweight rim be that affected by the 60mm valve stem weight that it un-balances it at high speeds? If it does, I am guessing a spoke magnet opposite the valve stem might work. Obviously with a mounted tire in the truing stand, the valve stem always ends up at the bottom, which you would expect in a balanced wheel.
 

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A 10g valve stem on a 700x23 tire at 40mph exerts a centrifugal force of approximately 1 lbf as it rotates 8.5 times per second.

It's amusing how reliably you assert that small differences are meaningless.
And the funny thing is that for most wheels, the rim joint is still heavier than the valve stem once a tire is mounted. So the valve stem is cancelling some (but not all) of the weight of the rim joint.

And if you want to claim that 1 lbf is enough to compress a tire pumped to 90 psi feel free to chase that down. The only way the rider could feel the forces of an out of balance wheel would be if the tire was compressing or the wheel speed was changing as it rotated. Do you think that something less than 1 lbf would cause that?
 

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Discussion Starter · #19 ·
Feeling. It started with a deeper aero wheels than I have run. I think it could be related to aero turbulence of the wheel at the fork. On days with less wind, it isn't as noticeable. So if I am moving 35 mph down hill, the turbulence increases with speed, so does the sensation. Almost like a harmonic problem. I have a Ridley Noah on its way (not related to this problem) and they claim to have a split fork that decreases turbulence. I will be curious to see if this helps.
 

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I've noticed that before on wheels with under- or unevenly-tensioned spokes.

Feeling. It started with a deeper aero wheels than I have run. I think it could be related to aero turbulence of the wheel at the fork. On days with less wind, it isn't as noticeable. So if I am moving 35 mph down hill, the turbulence increases with speed, so does the sensation. Almost like a harmonic problem. I have a Ridley Noah on its way (not related to this problem) and they claim to have a split fork that decreases turbulence. I will be curious to see if this helps.
 
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