If you are reading this than you have likely noticed that there are not a lot of options for someone who wants to use flat mount caliper on a post mount frame/fork. This is probably because it is very difficult for a manufacture to guaranty compatibility. However it may be possible, but it will depend on your frame/fork and the size of the rotor that you want to use. This guide is meant to help you determine which adapter you need and if it will work with your frame/fork.


Frame/Fork Compatibility

The first step is to determine which size post mounts you are using. The post mounts on most road or cyclocross frames have been designed for either 140 mm or 160 mm rotors.

160 mm post mount frame/fork:

  • 140 mm rotor – We don’t make an adapter that will work for this combination.
  • 160 mm rotor – Adapter: 160PM-160FM – You need at least 24 mm clearance between posts.Flat Mount Caliper on a 160 mm Post Mount Frame/Fork with 160 mm Rotor

140 mm post mount frame/fork:

  • 140 mm rotor – Adapter: 140PM-140FM – You need at least 24 mm clearance between posts.

    Flat Mount Caliper on a 140 mm Post Mount Frame/Fork with 140 mm Rotor

  • 160 mm rotor – Adapter: 140PM-160FM – You need at least 13 mm clearance between posts.

    140pm-160fm flat mount adapter drawing

Caliper Compatibility

The adapters were designed to have enough clearance for Shimano calipers. Most other calipers are smaller and should work without problems.

Campagnolo: Rear 140 mm calipers should work with all our adapters. Rear 160 mm calipers will only work on a 140 mm post mount frame with a 160 mm rotor, if you use the 140PM-140FM adapter. Front calipers won’t work with our adapters. (Ekar calipers will work with all our adapters.)


You can also download a drawing with the images from this page.

Flat Mount Brake Caliper on a Post Mount Frame or Fork


The drawing is 1:1 scale so If you print it on the correct size paper should be actual size. You can cut out the adapter you want to use and hold it up to the frame/fork to get a better idea if it will work.

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