Why is it that I can build a wheel that measures both radially and laterally true but when I spin it while holding the axle it "feels" as if it has a hop in it? Almost as if it were unbalanced. Really the only thing that would cause unequal weight distribution in the wheel may be the rim joint. Any ideas?
"As a kid, the first ride of spring for me was true freedom." The Wheel
Frustrating situation. Have you checked your axle. Maybe it's bent. I'd take a look at the bearings too, just to make sure there are equal numbers on both sides, properly lubed, cups/cones not scored. You did not mentioned if you spun this wheel after installing a tire & tube or tubular tire. IMHO, it's possible that it's a bad rim (poor joint).
Almost all wheels do that when you spin them in your hands. I think it has something to do with the valve stem hole. If you think about it, the valve hole side is lighter than the rest of the rim, and your arms just aren't as stable as a truing stand mounted to a bench. Does that make any sense to you?
Yes. It does make sense. Between the valve stem hole and the rim joint there would likely be enough weight imbalance to cause this effect. It varies from wheel to wheel. Non-existant in some to down right scary in others. Thanks for the responses!
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by squeaky wheel: Why is it that I can build a wheel that measures both radially and laterally true but when I spin it while holding the axle it "feels" as if it has a hop in it? Almost as if it were unbalanced. Really the only thing that would cause unequal weight distribution in the wheel may be the rim joint. Any ideas?
Because of the very light weight of a bicycle wheel and the relatively low speeds (80km/h) achieved, no one has really bothered to balance a wheel. Once the tube and tyre has been fitted, as well as the computer magnet, the valve, magnet, or rim joint, normally causes a heavy spot and if the wheel is held free to rotate, the heavy spot will find its way to the bottom of the wheel (6 o'clock). This is very easy to rectify, by balancing the wheel. Use the stick on balancing weights, used on automotive magnesium wheels, and cut a suitable small piece, which is then neatly filed. Place this 180 degrees opposite to the heavy spot and leave the wheel free to rotate. Adjust the size of this weight and it's position, untill there is no heavy spot. That means the wheel stops in any position when rotated.
If you spin your back wheel in a 53/13 gear, at high sped, while the bike is in a bike stand, an unbalanced wheel causes the whole bike to shake. This is actually lost energy. So if you balance both wheels, you actually go a little faster.