Shimano SM-MA90 Disc Brake Adapter

With the SM-MA90 Disc Brake Adapter, Shimano has taken an artful leap at the lowly disc brake adapter. Not only is it lighter than their older adapters, but it's more refined -- this refinement being the reason for its lightness. Where Shimano's older adapters were blocky, this one has curved edges. Where they were solid, this one has a window machined out of the center of the adapter body.

The Shimano SM-MA90 Disc Brake Adapter is available in five versions to fit 160 and 180mm rotors for front ISO or Post mounts and rear ISO mounts.

  • Reviews
  • Q & A

Make it allllll work!

    A must have to up your rotor size. Always great to upgrade!

    Adapt it

    • Familiarity: I've put it through the wringer

    Nothing better for running a larger rotor than the correct adapter. I used the Shimano adapter to go from a 160mm to 180mm post mount fork.

    So you went XTR

      We see that, and we respect that. Now, make sure that everything plays nicely together by making sure you use the correct hardware. These not only drop weight, but use a different bolt to match with the XTR calipers.

      Not just for 180

      • Familiarity: I've put it through the wringer

      Got the 180 post mount adapter. Essentially its a 10mm spacer used to increase rotor size by 20mm. Worked great with TRP HYRD to mount 160mm rotors on a Ritchey cross fork. Also used it to swap up from 160 to 180 front rotor on my mtb bike. Does what it needs to do.

      Lets you run a 180mm front

        What you'll need to run a 180mm front rotor (or bigger). Pretty much does it as advertised.

        What you will need!

          Makes mounting 180 rotors a snap! Works as stated and light weight.

          Highly Adaptable

          • Familiarity: I've put it through the wringer

          These can be a little confusing, call a competitive sales rep if you need guidance. The Shimano adaptors are primo, and work nicely with Shimano brakes, or whatever else you happen to be using.

          Mount up

          • Familiarity: I've used it several times

          Necessity when mounting disc brakes to a bike. Light and easy to install.

          used them with guide breaks

          • Familiarity: I've put it through the wringer

          I recommend using these instead of the sram break adapters for the guide breaks. easy to install.

          Basic excecution

          • Familiarity: I've put it through the wringer

          It is amazing that a seemingly basic component can be done in so many different ways at different degrees of successful execution. Shimano does theirs very well. keeps the caliper stable and in the correct position with very little, if any flex. You need this adapter for most builds today.

          Correct spacing

          • Familiarity: I've used it once or twice and have initial impressions

          Pretty much necessary for most builds nowadays, these are a great choice!

          I like big rotors

          • Familiarity: I've put it through the wringer

          So I use these to adjust my brakes.

          gotta have it

          • Familiarity: I've used it several times

          My fat bike came with hydraulic 160mm rotors in front and back. For winter, I wanted mechanical brakes and figured I'd upsize the front. Need an adapter to accommodate the 180mm rotor. I used this even though installing TRP Spykes with an centerline rotor--it's all working well together.

          Does the job

          • Familiarity: I've put it through the wringer

          Light, and a necessity for running larger rotors out back in 180 size

          Unanswered Question

          What is the difference between MA and MA90 Shimano PN brake adapters?

          Unanswered Question

          I have a 140 post mount rear and I want to use a 160 disc rotor, which adapter do I choose?

          180s 4eva

          • Familiarity: I've put it through the wringer

          I always upsize my rotors to 180, front and rear. These will get the job done.

          What is the Thin Metal Wire used for, that is included?

          you put it through the holes in the head of your bolts to keep them from coming lose

          just works

          • Familiarity: I've put it through the wringer

          used these to bring the rear up to 140 and front up to 160 on a specialized xc rig with xtr trail brakes

          Upgrade to 180

            I recently installed new rotors on my Santa Cruz Tallboy LTC. After riding a friends bike which had 180mm rotors front and rear, I decided I'd do the same. It's made a noticeable difference for sure. I got the Post for the front and the ISO option for the rear. Just a heads up sometimes ISO is referred to as IS.