Originally Posted by
Chombi
They are useful as you set the axle position relative to the upper pivot bolt of the rear deraillleur, as some RDS shift better with the right distance dialed in.
But once you set it you pretty much "forget it" but when it comes to taking the rear wheel off and back on, you will be sure that the axle is in the right place for best shifting and that your wheel will be straight between the stays.
Ahh, that clarifies things. I knew that they're supposed to let you put your wheel in the same position, each time, but I didn't know exactly why. Seems it'd be better, to just avoid certain trouble-causing RDs.
