Just trying to decipher the difference between Magura post mount sizes,if I want buy say a 203mm front brake setup from CRC why are there 6inch,7inch & 8inch post mount sizing? How do i know which one to go for, I thought post mounts on forks were a standard size? Please banish my confusion! 🙂

if you bolt the caliper straight to the fork (both post mount) then it should be 160mm (ie 6 inch)

if you want to fit a 203mm disc then you need a +20mm adapter – ie 8 inch.

but without a link to the ones you are looking at it sounds like they either come with the adapter you want and maybe the disc or they have calipers with the offset built in.

6″ = 160mm
7″ = 180mm
8″ = 203mm

use the difference in radius for the spacer required – ie +10mm for 160 to 180mm or +20mm for 160 to 203mm.

andyl-I understand about disk brake sizing so i dont understand why there would be an option for example for a 203mm disk with a 6inch post mount?? I would naturally assume as you mention that a 203mm disk option automatically come with an 8inch post mount size?! Seems abit strange that CRC could sell something that doesnt fit,i.e a 203mm disk brake with only a 6 inch post mount included?

Ahh,just reread your post,I’m starting to think that the 6,7,8 inch post mount sizing must relate to caliper offset so that an 8 inch post size wouldnt require an adaptor to run a 203mm rotor,however by using this option it then wouldnt be possible tn downsize to say a 180mm rotor in the future. I.e. 203mm disk 6inch post mount = 203mm rotor + 6inch caliper(to fit 160mm)+adaptor (to allow 203mm disk. Whereas 203mm 8 inch post mount = 203mm disk + 8 inch caliper (offset to allow 203mm rotor)+no adaptor required. That must be it!