This excerpt is from the Cambria website from which I am on the verge of finally buying my first official wheelset!: Ritchey Zero System OCR Pro wheels. I am confused exactly what they are referring to by giving me some sort of option between the 14 mm axle or 20 mm axle. I am 6' 2" and 198 lbs. Should I go for the 20 mm axle for stiffness? I also tend to ride my bike a little hard, as compared to babying it. Thus I hope durability over weight is what I'm looking for. ALSO, does OCR mean I will have a slightly offset rear wheel, or so I've read??
14mm Ritchey Skraxle CrMo QR/axle in one boosts front end stiffness or 20mm thru axle. 855/860/1075g
As high roller said, you have to have a fork built to take a 20mm thru axle to use one. Those forks don't have dropouts, they have a hole that the hollow axle slides through and binder bolts that clamp it in place thus the name "thru axle." More for freeride and DH.
The other axle is a quick release (QR) which most XC bikes are, prolly what you have.
As far as the offset part of it, it refers to the rim and not the wheel. All rims come to wedge shape on the inside and on most of them the center of the wedge shape is equidistant from the sides of the rim or braking surface. On offset rims that line is not centered, it is off to oneside, I believe toward the driveside of the rim. Even with offset rims your wheel and tire should line up in the middle of your rear triangle/chainstays. I'm sure the purpose is ultimately a stronger rim. As I sure you know the spoke angle on your rear wheel is different on each side, drive side vs. non-drive side. I haven't seen an explanation of how an offset rim improves this but feel pretty sure there's somekind of strength/durability benefit there.
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