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ShimanoSM-MA90 Disc Brake Adapter
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Item # SHI0547

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  • One Color, Post, 180mm ($11.95)
  • One Color, Rear ISO, 160mm ($11.95)
  • One Color, Rear ISO, 180mm ($11.95)
  • One Color, Rear ISO, 140mm ($7.45)
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Item # SHI0547

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.

  • Handy brake adapters for switching up brake style
  • Capable of adapting post mount or ISO mounts
  • Curved edges are streamlined for slick setup
  • Cutout window sheds weight on setup
  • Available for 140, 160, and 180-millimeter rotors
Tech SpecsWeight
Tech Specs
Shimano front ISO/Post and rear ISO
Recommended Use
getting calipers to fit correctly
Manufacturer Warranty
1 year

Actual Weight

Actual weights are measured in-house by the Competitive Cyclist team.

Have questions? Chat with a Gearhead



One Color, Post, 180mm
One Color, Rear ISO, 160mm
One Color, Rear ISO, 180mm
One Color, Rear ISO, 140mm

Reviews & Community


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Does the job like a boss

    This adapter does exactly what it's supposed to. If you have post mounts and want to size up your rotors, this is the one you need. Not sure anyone actually uses the included safety wire, but its cool that Shimano includes it.

    Works Wonderfully

    • Familiarity: I've used it several times

    It adapted my fork from 180 to 200. Its all I want in a brake adapter

    Best brake adapters

    • Familiarity: I've put it through the wringer

    Shimano makes the best brake adapters. I don't always run Shimano brakes but I always use their adapters. They are easier to set up than others on the market and seem to be the best design available.

    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.

        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!

        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.