How to choose the correct disc brake adapter

With this article, we want to give you all the knowledge and understanding you’ll need to be able to identify which brake mount standard you have, and which adapter you need based on the disc brake rotor size that you intend to use. It’s important to understand the 2 most common disc brake mount standards we currently offer in our adapters - International Standard (IS), and Post Mount (PM). 

Post Mounts

Post Mounts feature 2 threaded posts that stand off either the frame or fork. Up until around 2018, pretty much all suspension forks and frames would use a 160mm or PM6 direct mount. Now, with many bikes such as Enduro bikes becoming specced with larger disc brake rotors, you often see 180mm or PM7 direct mounts fitted to frame and forks too, so can be a little more confusing as to which direct mount size you have. Beyond this, 203mm or PM8 direct post mounts can be found on bigger travel suspension forks such as the Fox 40, where the caliper would bolt directly to the fork without the use of an adapter when running a 203mm disc brake rotor.

This image illustrates a 160mm or PM6 direct mount fork using a 160mm disc brake rotor. In this setup, no brake adapter is required, as the brake caliper direct mounts to the fork.


This image shows the installation of our 180mm disc brake rotor with a PM6 fork. With this setup, the adapter you need would be a Post Mount 6 to 180mm or PM6/180, so the first part stating PM6 refers to your frame or fork direct mount size, and the 180 part is the disc brake rotor size you intend to fit.



This image shows the installation of our 203mm disc brake rotor with a PM6 fork. With this setup, the adapter you need would be a Post Mount 6 to 203mm or PM6/203, so the first part stating PM6 refers to your frame or fork direct mount size, and the 203 part is the disc brake rotor size you intend to fit.

This image shows the installation of our 220mm disc brake rotor with a PM6 fork. With this setup, the adapter you need would be a Post Mount 6 to 220mm or PM6/220, so the first part stating PM6 refers to your frame or fork direct mount size, and the 220 part is the disc brake rotor size you intend to fit.

International Standard

 

International Standard mounts are the unthreaded tabs found on either a frame or fork. These allow for the brake adapter to be bolted to the IS tabs, then the brake caliper is bolted to the adapter. These adapters are front and rear specific, so an adapter for a fork would require a front, and the frame a rear adapter. Current fork manufacturers use almost exclusively post mounts now, but IS mounts are still commonly used on the rear of frames. As an example, if you were looking to install a 180mm disc brake rotor onto an International Standard fork, you would need a Post Mount to International Standard Front 180mm, or PM/IS-F180.



Note - Always check the frame and fork manufacturer specifications on the maximum rotor size you are permitted to fit, as exceeding the maximum specified size may result in frame/for damage.

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