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  1. #1
    mtbr member
    Join Date
    Jan 2004

    What would you suggest???

    I have pre-2007 XTR Disk brakes and happen to have an extra PM 74MM caliper. I currently have in the rear a IS 51MM caliper, but was thinking of switching it out for the PM 74MM caliper. My reasoning is, I like the way the Post Mount caliper adjusts much better. Just loosen the bolts and adjust. With the IS 51MM I have to use shims and it is a PIA. I do have an avid adapter to go from IS 51 to PM 74 for the rear. I am assuming the Avid adapter would work. What do you guys think? Should I just stick with my current set-up? Go with the 74MM PM? Pros and/or cons of either??? Other ideas??? Thanks for any help!
    Last edited by kevindef; 09-22-2008 at 03:08 AM.

  2. #2
    mtbr member
    Join Date
    Jul 2003

    No big deal, but...

    the problem you may run into is with your assumption that the Avid adapter will work with your Shimano caliper. It very well may not. The problem is, adapters and caliper are not standard! The only "standard" that has to do with calipers and adapters are the mounting hole locations and dimensions, i.e. 51mm IS, 74mm PM, bolt size and thread pitch, etc. From there everything is tossed into a cocked hat. Caliper shape, adapter shape and thickness, braking track, brake line attachment locations, angles and such, are all set by the individual brake manufacturer to match their specific calipers and rotors. And all of this may necessitate an adapter shape that is incompatable with other calipers. It's why there's a sticky up at the top of the forum entitled "Unsing Shimano Centerlock (or any other) with another brand caliper". Not even rotors are all exactly the same.

    With that said, all you can do is try it. Some manufacturers adapters will work with other manufacturers calipers, many will not. You'll need to pay attention to clearances when the caliper is mounted to the adpater and positioning of the caliper. If that's good then you'll need to closely examine where your pads make contact with the rotor. If the pads contact the braking track on the rotor the same as the old setup then you should be okay. If not then you'll need to find the appropriate Shimano adapter, if available, to make the swap.

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

  3. #3
    mtbr member
    Reputation: Aresab's Avatar
    Join Date
    Mar 2007
    I have Avid 160MM adapters in the rear as well as Shimano and Hayes w/ my74mm post mount calipers. At 160mm, all work fine. If you are using 180 in the rear, the Hayes will work bit the Avid is made for a 185 and will be too high for FULL pad contact. At 203, all will work well again(Hayes, Avid, Shimano)..

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