mattave

I'm sorry if this is a stupid question but do you need to adjust disc brake calipers when using different rotor sizes? If I accidentally got two 140mm rotors on my new CX wheelset but realized my current wheelset was 160/140 F/R. Am I safe to run 140 in the front if the bike came with a 160?

gsa103

If you can remove an adapter to get the caliper positioned for 140mm then yes. BUT the simpler solution is to just move the 160mm disc from your old wheels to the new wheels.

mattave

Thanks, I wasn't sure if there was an adjustment for calipers or not, I'll take a look. I'm building up a race wheelset so I'd like to have both working on the same bike. I guess I'm ordering a new 160 rotor!

RubeRad

There's probably a bracket that makes the caliper stand a little further from the mount to accomodate a larger rotor. 140 seems on the small end, maybe the caliper would line up with it well with no adapter at all. Otherwise you might have to get an appropriate adapter to replace your current adapter (or as gsa suggested, just keep using your old rotor)

Andy_K 

Cyclocross forks are typically made for 140mm rotors and need an adapter for 160mm, but MTB forks usually won't work with anything smaller than 160mm in the front.

fietsbob

I dont know of any way to use a 140 on the front ( short of custom ) a fork with a 140-160 adapter is 160 front , 140 rear
fronts same adapter = 1 size larger than rears a 140 front adapter in theory = 120 rear which does not exist.

you have 2 rear rotors now go buy a 160 .. if you had 2 160's that would mean you use a 160-180 adapter for the rear