Wheel roundness and balance

Stephen in Colorado has a question about his Shimano 7801 wheels, when he spins them the wheels seem to buck up and down in the frame; this is what we think he should do:

Question:
I have a Shimano dura ace 7801 wheelset with about 50 miles on it. If you put the rear wheel in the bike and flip the bike on its saddle and handle bars and spin it up to speed it looks like a bucking bronco through the frame, I took it to the bike shop and they trued and rounded it and then I told them the trouble etc and they said to use a 60 mm tube stem. I tried a 48 mm and it was terrible and then went to use a 60 and it was ok at fast speed but bad at lower speeds, I tried dura ace Mavic open pro wheels and they didn’t even move when spun up to speed or slowing down, I have tried the wheel in several bikes with same results, so what’s your opinion?

Thank you.

Hi Stephen,

From what you say it sounds like the bike shop have made sure that the wheel is exactly round and straight, so that is not the problem and so the reason the wheel seems to “bob” up and down has to be a weighting problem.

This is borne out by you trying the longer length valve, as obviously it is heavier and balanced out the slightly heavier weight at the joint on the rim which is opposite the valve hole. Looking at the Shimano 7801 wheels the joint is weighted and this would explain why it doesn’t do it with the longer/heavier valve, do you use the locking ring on the valve as this will also add a little more weight.

You will find that this only happens when you have the bike turned upside down or on a work stand. If you don’t feel anything when riding I wouldn’t worry about it as many wheels are not perfectly balanced due to the weight of the joint and the valve, but the wheels are perfect in all other ways and will ride as any other wheels.

Try to balance the wheels so that the valve and joint are of the same weight, you will know this when the valve and the joint are opposite each other when the wheel stops turning. If the valve or the joint is heavier then it will be lower than the other.

The Shimano 7801 are a great pair of wheels and you would be better just riding them and enjoying your cycling, I’m sure after all these years and experience Shimano know what they are doing.