These simple and strong adapters from Shimano create the proper spacing from the mount standard on your bike to the disc brake caliper type and/or rotor size. The Post Mount type matches to the 74mm post mount of the frame or fork, and act as a 20mm spacer so the caliper will sit at the proper height with 160mm or 180mm Shimano rotors. So if you have a road fork with a 74mm post mount that is set-up for a 140mm rotor, but you want to run a 160mm, that adaptor comes with long thru-bolts for an easy set-up. This same adaptor will convert a mountain 74mm post mount that is set-up for a 160mm rotor and allow you to run an 180mm rotor. Your caliper will dictate the options of the brake itself.

For 51mm International Standard (IS) mounts, the adaptor has two sets of bolt holes. The first set aligns side to side with with IS mount, inboard. Then you can mount your post mount caliper to the adaptor. SM-MA-R160 P/S is the rear adaptor and is only for 160mm rotors. The vast majority of current mountain and road frames and forks have moved forward from the IS style, with post mount dominating the mountain side. Road disc bikes have moved more towards a third standard, called Flat Mount. If you are looking for a Flat Mount adaptor, type 156020 into our Search Box above, and it will pull up that option.