Originally Posted by
CliffordK
I'm going to have to disagree on that one.
Skewers are designed to provide tension and not support. Many have smooth faces for just that reason. Those riders bending skewers are not getting the wheels set in the dropouts right, and are likely using them for support.
A very tight skewer can hold a rear wheel from sliding forward. I've ridden horizontal dropouts long enough to know that. But, you'll also find many threads about people's wheels shifting in the dropouts. Some are riders with vertical dropouts, and are twisting the wheel beyond its natural position before tightening. Then when they start riding, the wheels shifts back to its natural position in the dropout as dictated by the axle.
For steel/aluminum axle length may not make much difference. Damaging threads on axles? Thread damage to dropouts? I still like as much support as I can get.
For Carbon Fiber, there is a lot of discussion about not over-torquing the CF in most places on the bike. Why not the dropouts too? Especially on older bikes? In other places on the bike, the CF seems to be quite prone to problems with both too much compression as well as abrasion. Now, it might take years to grind out too much dropout, but I'd rather not toast my frame. Actually I have a bike sitting in the basement with CF front dropouts. I'm not quite sure what I'll do with it. Maybe at least find the right axle with end caps so it won't be sitting on the threads. And the stock skewers just don't fit right, only snagging a few threads and getting nowhere near the nyloc.
As the thread tangents- The situation you describe of a vertical drop out with an axle not filly seated isn't using the skewer for support. It's using the skewer's compressive force to create friction between the axle end and skewer end cap sandwiching the drop out between. The support of the axle's location isn't dependent of the skewer's bending strength.
The reason that carbon frames are so torque sensitive is for a few reasons. First is that the top layer of carbon can be soft and compressible. Hence the indents on some seat posts and steerers when over tightened. Second is that many frames clamping areas are designed to not have to resist compressive forces, the torque limits is suppose to prevent the crushing potential. The frame is instead designed to handle the other forces that a bike sees and use as little carbon as possible (for weight reasons). So components like a front der might be limited in torque to not crush a tube (and repair stands shouldn't be used on the tubes.) Drop outs are a different situation as they are not hollow (or all I know of are not). The early carbon frames (and many still today) have AL or other metal drop outs so these have the same limits and procedures as an all metal frame would have WRT the drop out use. More recent carbon frames have completely carbon formed drop outs. One hopes that they have been engineered to withstand far greater surface compressive forces then the tubes and clamping areas of the same frame. Without the hollow of a tube the structural shape should be far easier to maintain. Time will tell as to the other degradation that drop outs see. Andy