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  1. #1
    mtbr member
    Join Date
    Aug 2007

    Need help with post mount adapter

    I have a new cross frameset that comes set up for a 140mm post mount front and rear disc brake. I have all kinds of IS mounts laying around, but not a lot of experience with post mounts. The bike is going to be used for fire roads and light singletrack, and occasionally some cross racing. I want to run a 160mm front rotor, but for the life of me I can't find the right adapter.

    I bought the avid adapter, but can't seem to make it work. It needs the CPS washers to work, but when I add them, it is spaced way too tall for the rotor.

    Can someone tell me what they are using, or point me in a different direction?


  2. #2
    B A N N E D
    Join Date
    Apr 2007
    If you have post mount brake calipers and the fork/frame have post mounts set at 140mm specs you'd need the following adapter.

    It's listed as a 180mm adapter because most post mounts are set at 160mm specs.

    With 160mm post mounts it will increase the rotor size by 20mm to 180mm
    With 140mm post mounts it will increase the rotor size by 20mm to 160mm

    That adapter will work on front and rear post mounts.

    The following photo shows 140mm Post Mounts with 20mm (180mm) PM to PM adapter and a 160mm rotor

    Need help with post mount adapter-1353939709345-1wz1ubnvi74c5-670-75.jpg

  3. #3
    mtbr member
    Join Date
    Aug 2007
    Cobba- Thanks. That will work. I was hoping to find an adapter that didn't need the CPS washers, and instead was just a spacer. But maybe that doesn't exist. Ordering one of those now.

  4. #4
    B A N N E D
    Join Date
    Apr 2007
    Adapters don't need CPS washers, only Avid brake calipers need CPS washers.

    If you don't have a Avid brake caliper then you wouldn't use CPS washers between it and the adapter.

    That Avid adapter is basically the same as the following 3 adapters and they will do exactly the same thing as it.

    When using the 180mm adapters you'll probably need to use CPS washers between the bolt head and the caliper like in the following document.

    CPS type washers are used with 180mm adapters so the bolt head will tighten down properly on the brake caliper.

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