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  1. #1
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    Machine new disk mounts?

    I just bought a set of Marta SLs and the instructions say to have the disk mounts machined or "faced" prior to mounting the calipers. Is this really necessary? Does it make a big difference?

  2. #2
    Kam
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    not necessary...

    you'll probably have to shim the caliper towards the wheels (inboard), so i think having your disc mount faced isn't necessary. but, facing is necessary when you have to bring the caliper outboard (away from the bike) since you can only move the caliper outboard by shaving (or "facing") the mount.


    i have a '03 xtr disc caliper i tried to use on my rigid single speed (i have kelly disc fork and a king iso disc hub) and i had to bring the caliper outboard, so i filed some of the thick @ss paint off the disc mount (not recommended). this still didn't work out for me, so i took a hope mono mini off my other bike...and horray!!! no shims needed and perfect alignment.

    imho, facing isn't necessary unless you need to bring the caliper outboard (away from the wheel). if you have to get it done, it will be tough finding a shop to do it...most do not have the tools and others don't have a clue to what disc tab facing is. and, this is coming from a guy who lives in los angeles.

    cheers!

    Quote Originally Posted by Pinhead
    I just bought a set of Marta SLs and the instructions say to have the disk mounts machined or "faced" prior to mounting the calipers. Is this really necessary? Does it make a big difference?

  3. #3
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    It's nice, but not absolutely necessary. Shims still do the job most of the time.

    Magura maybe trying to pimp and promote their disc brake tab facing tool that they are selling to bike shops.
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  4. #4
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    The reason to face the mounts is so they are aligned properly (parallel) with the rotor. Shims alone may not be able to fix it.
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  5. #5
    UKMac
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    Absolutely face the mounts

    It's cheap at a good shop and will help avoid frustrating power and noise problems! The point of facing is to get the mounts square with the dropouts; the shims just center the caliper over the rotor. My friends in a high end custom MTB shop won't let any frame or fork out without facing it first. Even the paint on frames and forks can be enough to cause problems.

  6. #6
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    With some forks and hubs, you MUST face the tabs. For example with the Fox/King combo, you need to remove about 1mm of material from the disc tab for the caliper to line up at all. On other forks, as the others said, it will eliminate a lot of squealing problems. Just do it.
    Long Live Long Rides

  7. #7
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    Quote Originally Posted by Pinhead
    I just bought a set of Marta SLs and the instructions say to have the disk mounts machined or "faced" prior to mounting the calipers. Is this really necessary? Does it make a big difference?
    As others have mentioned, if you have a LBS that has a Magura or Hope tab facing tool, then get them to do it. This will remove any excess paint, metal, etc from the tabs and will ensure that they are perfectly parallel with each other and the rotor. This will eliminate noise, vibrations, etc. that may resonate from the brake should the caliper be skewed relative to the rotor.

    In my case, I'm using a Fox F100X, Marta SL and King ISO combo on one of my bikes. This particular combination resulted in the caliper sitting too close to the rotor. Even though the Fox tabs had been faced by the LBS, I had to re-face the tabs an additional ~1mm so that I could center the caliper properly over the rotor. Until I had access to the Gnann-o-mat, I used a thin (0.8mm) washer on the disc-side of the King axle, which effectively shifted the Fox's disc leg out and give me the clearance I needed. Not ideal, but it worked perfectly!

    My other bike is using a Fox F80X, Marta SL and Hope Bulb combo and it is perfect!
    Ride Hard,
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