Originally Posted by jmX
The frame is aluminum, and I'm not sure if using washers would really allow for enough engagement in the dropouts for me to feel safe. I'll look into that tonight when I'm at the bike.
2.5mm for each side doesn't seem like much...maybe the rear will flex enough to clamp down on the wheel properly, I don't know. Even if I did get it securely clamped in I'm not sure how that affects the chain line - I assume I'll have to re-setup the high/low limits on the rear der.
You won't need to change a thing with the RD if you keep the cogs in the exact place they are now. The extra 5mm goes on the left
side of the hub to reduce wheel-dish. The cogs are in the same location relative to the right dropout and derailleur on a 130 or 135mm wheel. Please "remove" with "add" in the picture below:
Also it's the friction between the dropout and locknut face that transmits the loads to the bearings, then to the bearings and hub-shell. The QR skewers generate the tension force and friction (f=uN) that keeps the locknut from moving relative to the dropout face. The skewers only face tension forces, never any vertical-loading.
If it was only the skewers that held the wheel on, you would have vertical movement of the axle relative to the frame because the hole in the axle for the skewer is larger than the skewer itself. With horizontal dropouts, you can have a skewer with smooth clamping surfaces and it will hold a wheel just fine if the locknuts are serrated. However, serrated QR nuts won't hold a hub with smooth locknuts very well and requires a lot more clamping force than the 1st scenario.