Originally Posted by
Jeff Wills
On most horizontal dropouts, pulling the axle all the way back in the slot will result in poor positioning of the derailleur in relation to the freewheel. As I said before, the axle should be positioned directly above the main derailleur ("B") pivot.
Like this (yeah, it's a vertical dropout):
Not like this:
Yup, I beleive thats the reason most clamp on derailuers lock out part of the drop out so the wheel naturaly falls there. I've even been noticing dept store bikes (schwinns in the cases I've seen) where the drive side dropout doesn't run as far back (a really stupid system imo but much cheaper than getting good enough facilities for tighter tolerances alowing vertical dropouts)