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  1. #1
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    XT 775 Front Caliper Issue

    Hi Guys

    Thought I'd post a tricky one for you today

    I recently changed the pads in my XT 775 Front Caliper. Instead of going with the specific XT 775 Resin Pads, I went with the older XTR 965 Resin Pads.

    I assumed that these being exactly the same shape/fitment that all would be grand and everything would work well.

    Now, since the change, I have found that when out of the saddle and climbing/applying front end pressure. The wheel (XTR HUB, XC717 Rim, Revo Spokes)/disc (180mm XTR Centrelock) is making a rather metallic rubbing/grating sound which is not apparent in general "in saddle" riding.

    It sounds to me like the rotor is rubbing on something within the caliper, but my question is WHAT?

    Has anyone else faced this type of problem? Is it an incompatibility between the pads and calipers? Are they that different?

    I was considering swapping the rear pads (775 fairly new) to the front, but want to understand the issue first!

    For reference, I have reset the pistons, ensured the rotor is true and even taken the disc off the wheel and ridden it up and down my road to ensure it's not a wheel/spoke tension issue.

    Any help would be grand

    Andy

  2. #2
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    Did you clean the pistons before resetting them? Have you checked that the pad spring is properly seated? It could be something as simple as the new pads having more pad material, or a thicker backplate, which is leaving you with too small an aperture for the rotor to run through. Did you have to pump the lever much when you first operated it after having reset the pistons?
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  3. #3
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    Yup, pistons cleaned... I did check the pad spring and it seems perfectly seated. I didn't have to pump the lever excessivley after the reset, they have a very good feel (identical pretty much to the rear). I can always see how it goes as the pads wear, but.. it's just annoying because it doesn't sound "healthy"!

  4. #4
    DGB
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    I had a similar problem with rub when I changed to a new set of pads (M06 Metal pads) but I've found that this goes away once the pads wear a small bit. After the first ride the rub was pretty much gone and the brakes were working brilliantly again.
    It's definitely not incompatibility as those M775 (A01S) pads can be used in the other shimano compatible calipers no problem.

  5. #5
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    Check your caliper alignment. If the caliper is slightly crooked, the disc can rub on the edge of the caliper itself, in front of or behind the brake pads, when you apply some additional torque to the front wheel on a standing climb. Also check the clearance between the outer edge of the rotor and the caliper - I run Hayes V8 rotors and have to run a thin washer between the adapter and caliper to keep the square edges of the Hayes rotor from rubbing the sides of the round cutout on the caliper.

  6. #6
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    Did you check your hub for play? When you shift your weight to the front hub it could change your alignment very slightly with a bit of play in the hub.

  7. #7
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    Just wanted to thank everyone for their input on this problem! I haven't had a chance to check back as I've been away.

    However, I stripped the caliper down again, reset the pistons, removed the rotor and started again.. it seems alot better, I also repositioned the caliper on the fork which seems to give a little more clearance.

    I think in order to completely remove the issue, I will swap the front pads for the rear as the front wheel is bound to flex more under pressure.

    Thanks again

    Andy

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