Originally Posted by
Retro Grouch
Axle lengths for QR hubs have to be exactly the right length. If they project beyond the dropouts AT ALL, they won't clamp.
I wouldn't say there's anything 'exact' about axle lengths for a QR hub. As you correctly state, as long as the axle does not protrude past the dropout and protrudes just a bit beyond the lock nut (allow for alignment in the frame) it'll work. That usually gives one a margin of at least 10mm on the 'right' length.
I added QRs to my nephew's MTB to make it easier to transport in the trunk of my sister's car. Cost about $20 using parts from Niagara Cycle.
Here's what I used:
Summit Front QR Axle Set M9/100X108mm 800012 1 $4.38 USD
Summit Rear QR Axle Set M10X135X140mm 800014 1 $4.38 USD
XLC Quick Release Skewers, Pair, Black 600594 1 $9.48 USD
Edit: Just recalled that I did need to order some additional spacers to get the rear hub in spec. Probably another $5 max.