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  1. #1
    bikerpilot
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    2013 Avid X0 caliper mounting configuration questions

    Just picked up my BMC FS01 with X0 brakes and 180mm rotors. I wanted to switch to 160mm rotors to standardize across my bikes. I ordered the rotors and a couple of CPS mounting kits, knowing the bolts with the 180 adapters would be too long. I went to mount them up last night and thought they didn't quite look right. I checked on Avid's site and found their mounting guide:
    http://cdn.sram.com/cdn/farfuture/aw...mounting_0.pdf

    According to this, I think the X0 caliper should mount directly to the post mounts on the Fox fork and frame (without CPS washers), as shown in image G. This is based on the X0 caliper being a "standard" caliper, not a CPS caliper. Does anyone know if this is correct?

    If this is correct, then that means with the stock 180 rotors the calipers should've been mounted as in image I with post spacers. Instead they came with a post bracket and one set of CPS washers on top as in image J. However, image J is only applicable with a combination of 140 post mount and a 170 rotor.

    To make things even more confusing is that on the XO brake page, a 160 rotor is shown and the caliper has a post bracket with one set of CPS washers, as in image J. According to the mounting guide this is never a valid combination.

    Any clarification on what mounting I should use to mount 2013 X0 calipers to an F29 with 160 posts and frame with 160 posts would be much appreciated. It could be that the mounting guide above is for 2012 and the 2013 calipers have changed, but I can't find a mounting guide dated 2013. Without that info I'm lost.

    (please don't devolve this into "you should just get shimano or maguras") Thanks.
    BMC FS01 29 X0
    Redline Monocog 29
    Jamis Supernova
    Rocky Mtn Flow DJ

  2. #2
    rebmem rbtm
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    Check how your pads line up with the rotor.

    If the pads overhang the outer edge of the rotor by about 5mm with the CPS washers on, you'll need to removal of CPS washers.

    If the pads are about 5mm away from the outer edge of the rotor without the CPS washers on, you'll need add the CPS washers.

    If your frame and fork have 160mm post mounts and you're using 160mm rotors it shouldn't be too hard to workout whether you need the CPS washers or not.




    .
    Last edited by cobba; 01-17-2013 at 08:41 AM.

  3. #3
    bikerpilot
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    Yeah, that's what initially tipped me off to the fact that they didn't look right, they didn't seem to be lining up. I think I figured it out, if the X0 caliper is indeed a "standard" and not a CPS caliper. Page 52 of this: http://cdn.sram.com/cdn/farfuture/GP..._spc_rev_a.pdf has a list of hardware, I needed item 1b to switch to the 160 rotors but got item 1a instead because I wasn't aware they had done away with the CPS on some calipers. Should've researched fully before!
    BMC FS01 29 X0
    Redline Monocog 29
    Jamis Supernova
    Rocky Mtn Flow DJ

  4. #4
    mtbr member
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    rock the 180mm rotors, they will stop you better than 160's. probably why they are specd on that 29er to begin with.

  5. #5
    bikerpilot
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    Quote Originally Posted by DOCRIGID View Post
    rock the 180mm rotors, they will stop you better than 160's. probably why they are specd on that 29er to begin with.
    I live in Houston, no hills around here big enough to make good use of the 180s. I've been riding 180s for the past year and the increased power was noticeable but again not at all needed and 160s had always been adequate before. I've already got 160s on a couple of wheelsets so I'd rather they all be easily interchangeable. If I don't feel like the 160s are enough maybe I will put the 180s on the front wheels and keep the 160s on the rears. I will keep the 180s for trips to CO and such though.
    BMC FS01 29 X0
    Redline Monocog 29
    Jamis Supernova
    Rocky Mtn Flow DJ

  6. #6
    rebmem rbtm
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    Quote Originally Posted by tootall View Post
    I checked on Avid's site and found their mounting guide:
    http://cdn.sram.com/cdn/farfuture/aw...mounting_0.pdf
    I think there's some flaws in that pdf.

    There's about 5mm difference between a 'Standard Caliper' and a 'CPS Caliper' or the thickness of the CPS washers.

    A 'Standard Caliper' has to be mounted onto a post mounts or an adapter without CPS washers, if CPS washers are used with this caliper it will be packed out too much and the pads will overhang the outer edge of the rotor.

    A 'CPS Caliper' needs to be used with the CPS washers to pack it out at the correct spacing.

    There is no '20 P' or '20mm Post' adapter in that document but they have instead the '20 S' or '20mm Spacers'.

    Avid 20mm Post Mount Adapter

    The '20 S' or '20mm Spacers' have the CPS built into them, this makes them the same size as a '20 P' or '20mm Post' adapter with the CPS washers added.

    When a '20 P' or '20mm Post' adapter is used with 'CPS Caliper' the CPS washers must be used but when it's used with a 'Standard Caliper' the CPS washers aren't used.

    Images 'C' & 'I' show the same '20 S' or '20mm Spacers' used but image 'C' is for a 'CPS Caliper' and image 'I' is for a 'Standard Caliper'.
    Image 'C' is referenced for mounting the 'CPS Caliper' on 140mm Post Mounts for use with a 160mm Rotor & on 160mm Post Mounts for use with 180mm Rotor.
    Image 'I' is referenced for mounting the 'Standard Caliper' on 140mm Post Mounts for use with a 160mm Rotor & on 160mm Post Mounts for use with 180mm Rotor.

    As a 'Standard Caliper' doesn't need the extra spacing of the CPS washers the '20 S' or '20mm Spacers' would pack the caliper out too much.



    According to this, I think the X0 caliper should mount directly to the post mounts on the Fox fork and frame (without CPS washers), as shown in image G. This is based on the X0 caliper being a "standard" caliper, not a CPS caliper. Does anyone know if this is correct?

    If this is correct, then that means with the stock 180 rotors the calipers should've been mounted as in image I with post spacers. Instead they came with a post bracket and one set of CPS washers on top as in image J. However, image J is only applicable with a combination of 140 post mount and a 170 rotor.
    Image 'J' is for a '30 P' or '30mm Post' adapter, it's only listed for use with 140mm Post Mounts and 170mm Rotors because if it was used on 160mm Post Mounts you'd need to use a 190mm Rotor which nobody makes.

    Your setup would of had a '20 P' or '20mm Post' adapter which isn't mentioned in that document and seems to have been replaced with the '20 S' or '20mm Spacers'.

    Maybe your bike had the '20 P' or '20mm Post' adapter because the '20 S' or '20mm Spacers' don't work properly with a 'Standard Caliper' as I previously mentioned.


    To make things even more confusing is that on the XO brake page, a 160 rotor is shown and the caliper has a post bracket with one set of CPS washers, as in image J. According to the mounting guide this is never a valid combination.
    The CPS washers on top of the caliper are no problem.
    If the flat surface of the adapter that the caliper sits on isn't at 90 degrees to the bolt then the caliper won't be at 90 degrees to the bolt either, if the caliper isn't at 90 degrees to the bolt then the bolt head won't be able to put a even downwards tightening force down on the caliper, it'll only be tightening down in one little area of the caliper.
    The CPS washers allow the whole bolt head to put a downwards tightening force on the caliper.
    Last edited by cobba; 02-03-2013 at 10:51 PM.

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