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  1. #1
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    7" adapter for Post Mount

    I'm currently running a 6" rotor on the front of my bike (fork is 6" PM) and would like to switch to a 7". I'm running Formula OROs and I know there's a specific adapter but was wondering if there's any downside to running these:

    It seems that there's no point in having all the extra material that the stock Formula adapter has, or am I missing something?

  2. #2
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    Ummm...

    yeah you are missing something. The adapter is needed to form a bridge between the two posts. With a 6" rotor the caliper is sufficiently strong to do this and keeps the load even between the upper and lower post. As the rotor gets larger the lever moment increases and puts more load on the lower post when braking. This can lead to thead fatigue, cracked mount, or broken mounting bolts. It likely won't happen imeidately, it'll may take some time. But given the right circumstances and/or enough time it will happen eventually.

    Unless both the fork and brake manufacturer specifically appove of a bridgeless adapter for larger rotors, the correct adapter is highly recommended.

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  3. #3
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    Reputation: AL29er's Avatar
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    Personally I prefer the Shimano and Magura mounts that bolt to the fork independent of the caliper. Either should work with the formula caliper.
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    Quote Originally Posted by saturnine
    that's the stupidest idea this side of pinkbike.

  4. #4
    human dehumidifier
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    Quote Originally Posted by AL29er
    Personally I prefer the Shimano and Magura mounts that bolt to the fork independent of the caliper. Either should work with the formula caliper.

    Much better than Avid's adapter that has you juggling the adapter, CPS washers, the bolts, the caliper ... I wonder if they'd work with an Avid caliper?
    I may or may not be laughing at you.

  5. #5
    Nouveau Retrogrouch SuperModerator
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    Quote Originally Posted by Gruzovik
    I'm currently running a 6" rotor on the front of my bike (fork is 6" PM) and would like to switch to a 7". I'm running Formula OROs and I know there's a specific adapter but was wondering if there's any downside to running these:

    It seems that there's no point in having all the extra material that the stock Formula adapter has, or am I missing something?
    And make sure you get the correct mount for your rotor size as there are no 7" (177.8mm) rotors. They can be 180, 183 or 185mm.
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  6. #6
    29 some of the time...
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    Quote Originally Posted by wv_bob
    Much better than Avid's adapter that has you juggling the adapter, CPS washers, the bolts, the caliper ... I wonder if they'd work with an Avid caliper?
    They should. I currently have the 203mm shimano on my Juicy caliper. You might have to trim the tabs on the outer brake pad to use the 180mm adapter. I have a 180mm magura rotor and adapter in the spares box, just haven't gotten around to trying it yet.
    Quote Originally Posted by saturnine
    that's the stupidest idea this side of pinkbike.

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