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Upgrading 160-180mm rotor on a fox f29 fork. (x-post)

2K views 2 replies 2 participants last post by  denhamcla 
#1 ·
Hey guys, i have the m485 shimano hyros that come with my gf, but i want to upgrade the front to a 180 rotor. Now I'm having difficulty grasping the IS/IS, IS/Post and all that jazz. I know the adapters are different depending on the fork and brakes, so if someone would be kind enough to link the proper adapter... hopefully a cheap one it would be a great help. I know the shimano parts, but they all seem to be 30$ while the 3rd parties seem to be like 6 or $7. And feel free to go into depth about the meaning behind the differences between the varying models. Thanks again guys. :thumbsup:
 
#2 ·
Okay it's pretty simple....

first you'll be MUCH better off getting a Shimano adpater. The reason being is not all brake calipers are created equal. Different shapes, mounting tab thicknesses etc. on the caliper make them unique and the adpaters are designed around the caliper. So, one compaines adpater won't necessarily work with another companies brake caliper. Unless you find an outfit that is makes an adpater specifically for the BR-M485 brake, forget it.

The difference between post mount and IS fork mounts is easy. A post mount is just that, there will be two posts on the back of the left fork leg that stick directly out to the rear of the fork leg. The threaded holes for mounting of the caliper (or adapter and caliper) will be bored directly into them. For a 160mm rotored brake the caliper will be mounted directly to the posts, no adapter needed. An IS fork mount will appear differently. They will be tabs that stick out from the left fork leg near the bottom but will have the holes bored lateraly (from left to right) when viewing the fork leg from behind. The bored holes in a post mount will be threaded to accept the mounting bolts. IS tabs are not threaded and require an adapter no matter what size rotor you use, the holes in the adapter are threaded to accept the mounting bolts in the case of the IS mount. Now to confuse things even more, Shimano used to make "direct mount" is calipers that had threaded holes in the caliper body that would mount directly to IS tabs for and allow for use of a 160mm rotor without an adpater. But don't worry about that, the M485 brake isn't of that type. The tough part is determining how your caliper is set up. Some calipers have a 51mm spacing between the mounting holes, some have a 74mm spacing. In the case of the M485 the spacing is 74mm so it makes it easy. It's designed to mount directly to a 74mm post mount on a fork for 160mm rotor, and only needs adapters for 180mm or 203mm rotors. So what you are looking for is a post mount to post mount adapter. Anything that says 51mm to post or 51mm to IS or 51mm to 74mm you can ignore.

What you will need is pretty simple as well. The F29 Fox uses post mount adapters and the M485 brake should be bolted directly to the post mounts on the fork if you are currently using a 160mm rotor. What you will need is a post mount adapter for a 180mm rotor, Shimano part number SM-MA-F180P/P, MFG# Y-817 34100. Search around online, if you can't track one down that way then you may have to get a local shop to order one for you. Usually the Shimano adapters run around $19.00 online depending on the adapter.

Good Dirt
 
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