Riders and mechanics fitting a post mount caliper to a flat mount rear frame with a 140 mm rotor.
Modern road and gravel frames usually use flat mount brake tabs, while plenty of calipers, including many mechanical and older hydraulic models, are post mount. The Shimano SM-MA-R140P/D bridges the two at the rear of the bike.
It bolts to the flat mount on your chainstay and gives you post mount tabs to fit the caliper to, positioned for a 140 mm rotor. The adapter is marked for 140 mm rotors only, so it won't give correct alignment with a larger disc.
It's a genuine Shimano part made to the brand's standard, so the caliper sits where it should and the pads meet the rotor squarely.
Flat to post mount
Fits a post mount caliper to a flat mount frame.
Rear specific
Designed for the chainstay mount.
140 mm rotors
Positions the caliper for a 140 mm disc.
Genuine Shimano
Made to Shimano's mounting standard.
Adapter
Great for
Maybe not for
Rear, flat mount frame to post mount caliper, 140 mm rotor only. Check that the supplied bolt length suits the thickness of your frame's rear mount before fitting.
Aligning the caliper
Fit the adapter, hang the caliper loosely, then squeeze the lever and snug the caliper bolts while it's held. Spin the wheel and fine-tune until the rotor runs clean between the pads.
Bolt length matters
Flat mount frames vary in mount thickness, and a bolt that's too long or short won't clamp safely. If you're unsure, bring the bike in and we'll check it.
