Originally Posted by
Mr. Fly
Well, we'll have to disagree here about both your "short spoke" theory and about spokes being the effective limiter of wheel life. I have a few wheels that have seen two or more rims without ever changing spokes (or hubs). The rims died from a variety of factors, ranging from puncture from normal wear-n-tear (over >10,000 miles) to crash damage to spokes pulling through while JRA.
These spokes are mostly DT Revolutions so they are not exactly the toughest spokes around. However, I did follow Jobst Brandt's method of stress-relieving the spokes after building the wheels. Brandt maintains that as long as the spokes are aligned and stress-relieved during build, they should last effectively indefinitely. He further maintains that spoke breakage is really symptomatic of an inadequate build. Finally, he claims some of his wheels had seen about 100,000 miles (and many rims) without spoke issues, and my experience supports his claims.
Do you accept the premise that a smaller wheel is a stronger wheel? If so, what is the difference between a smaller wheel and a larger wheel? The length of the spoke. Suppose you could shorten the length of the spoke so that it was exactly the same size as the spoke of a smaller wheel. There's no difference between the two wheels now except that the larger wheel has a larger rim (which
would add strength to the wheel).
You may wear out the rim's braking track but that's not related to the strength of the wheel. That's related to wear.
Look at the number of posts on failing spokes that occur with frightening regularity on this forum. There seems to be an endless supply of those posts. Failure of the rim due to the strength of the material is almost no existent. I've had a few spoke pull out of rims and I've had some rims crack on the second wall of a double wall rim. But, by far, the greatest number of wheel failures I've experienced have been due to broken spokes.
Originally Posted by
dscheidt
Not on planet Earth. Planet Stuart, which seems to have very different physics from planet Earth, that might be true. But most of us build wheels to work on Earth, where the wheel is supported by the reduction in tension of the spokes on the bottom.
If you really think about the way a wheel works, at the bottom of the wheel, the spoke isn't supporting the load. That's exactly what is happening when the spoke's tension is decreased at the bottom of the wheel. The spokes on top of the wheel are experiencing increased tension and pulling the wheel upward. Gravity is pulling the whole bike down so the wheel is hanging from the upper spokes. Since the wheel is hanging from those spokes, the load on the wheel is hanging from the spokes - i.e. you.
Visualize the wheel this way. Think of a detensioned wheel. Perhaps even one that has spokes that are too long. Allow the spokes to move freely within the rim. Hold the wheel horizontally and look at what happens to the spokes. The top ones are in contact with the rim. The hub hangs from those spokes. The bottom ones aren't in contact with the rim. The rim is free to move up in relation to their position. If you deflect the rim by putting it on the ground and pushing down, the bottom spokes won't do anything to prevent that deflection. That's because the wheel can't stand on the spokes at the bottom of the wheel because there's nothing to stand on.
Originally Posted by
dscheidt
In fact, rim failure is the only method that properly built wheels, which haven't been crashed or otherwise abused, fail on planet Earth.
The operative word is
properly. But wheels aren't always properly built. Like I said above, we see people complain about broken spokes all the time on these forums. How often do you see threads started on broken rims?