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  1. #1
    Uncle
    Reputation: Entrenador's Avatar
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    How to get the best performance from XT brakes?

    Hi. My rigid 29er is working now (and working better than at first), but the brakes are suspect still.

    I'm using XT m765 brakes with a 180mm A2Z rotor in front and the XT 160mm rotor in the rear. Initially, I had eBay generic/organic pads. These faded/smoked during my first decent descent (~500-600' maybe?). Since then, I rescuffed the rotors, cleaned with alcohol, and installed new shimano xtr organics. I bedded them lightly before riding trails. They're certainly working better, but on a recent & similar descent, the front began to fade a bit -- no burning smell, but the lever got a bit soft near the end, and the rear rotor looks like it was baked a bit (slightly tinted color since last descent.)

    Other details: 195lb (geared up) rider on Northern California XC trails, some reasonably steep & long. Since it's fully rigid, I brake pretty regularly while descending. Wheels are respectably light 36 hole type.

    I think the rotor diameter should be adequate, as I've managed very well with my165mm/145mm rotors on my 26er (older Hope minis are still working well). I'm open to trying a different composition pad, or replacing the front rotor with a more effective design if need be.

    Questions: What do I need to do to get the optimal performance from these brakes? -- should the 180mm A2Z rotor work fine, or are they (A2Z rotors) less efficient than more expensive/different type rotors? Is the organic compound not ideal (felt good but seems prone to heating up too much)? Would a larger rear rotor solve my problems? With the somewhat narrow brake track, are these brakes destined by design to over-heat no matter the pad composition? Can I expect better performance from another pad maker/composition, and if so which one? Lastly, any rotor damage concerns by switching to a different pad compound? (This last question comes after the LBS showed me a few trashed rotors that were supposed to be the result of using metallic pads.)


    Thanks for sharing your detailed experiences with these seemingly quality brakes.
    105mm
    Last edited by Entrenador; 06-25-2008 at 02:02 AM.

  2. #2
    Meh.
    Reputation: XSL_WiLL's Avatar
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    Shouldn't be any issues with using metallic or semi-metallic pads. I've never seen steel rotors damaged by the friction material... only when the material has worn/fallen off and it's the backing of the pad hitting the rotor. Unless it's some crazy super abrasive pad.

    You can also try the DH compounds produced by Galfer or EBC. But typically the sintered metallic pads will fade less because it transfers heat to the rest of the system. The organic pads act like an insulator and the rotors get heat bounced back at it.

  3. #3
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    I ran the same calipers on 180/180 XT rotors for a while. The Galfer red pads made a huge difference. I've tried XTR and (obviously) the stock XT pads, they don't even come close. Aren't the A2Z rotors the light weight serrated ones they've been going on about in the WW forum for a while? I tried running a set of those in 180mm front and rear with the XT calipers and was amazed at how much they sucked. It was a surprisingly short trip to fade city. You might try a "normal" rotor up front and see if that helps.

  4. #4
    Uncle
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    Another Galfer plug...

    Quote Originally Posted by wreckedrex
    Aren't the A2Z rotors the light weight serrated ones they've been going on about in the WW forum for a while? I tried running a set of those in 180mm front and rear with the XT calipers and was amazed at how much they sucked. It was a surprisingly short trip to fade city. You might try a "normal" rotor up front and see if that helps.
    Lots of positive mention of Galfer pads on MTBR. Might go that route next. The A2Z rotor is the one here marked TY-180. Doesn't seem to be serrated -- just a simple rotor with plain ol' circle holes:

    http://www.a2zcomponents.com/tepp.htm

    Heat transfer question: If I go from organic to metallic pads, won't that transfer heat to the caliper more quickly? Asking because on my most recent descent, I did feel the lever go soft a bit. Doesn't the soft lever indicate that the caliper is heating up already, even with the organic pads? Or, is the mushy lever the sign of the organic pads glazing up?

    thx
    Last edited by Entrenador; 06-25-2008 at 01:35 PM.

  5. #5
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    Ah, A2Z makes the one I mentioned, but yours is not it. A soft lever sounds like hot fluid to me, but I'm far from an expert. I don't think the metalic pads will transfer much more heat, they'll just be harder to glaze. More rotor and/or a bleed are the only things I can think of to combat fade due to hot fluid.

  6. #6
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    Ordered Galfer semi-metallic pads today

    Quote Originally Posted by wreckedrex
    Ah, A2Z makes the one I mentioned, but yours is not it. A soft lever sounds like hot fluid to me, but I'm far from an expert. I don't think the metalic pads will transfer much more heat, they'll just be harder to glaze. More rotor and/or a bleed are the only things I can think of to combat fade due to hot fluid.
    I wasn't ready to deal with the howl of fully metallic sintered pads yet, so after seeing lots of praise here on MTBR for Galfer, I pulled the trigger. If organics give good feel but moderate stopping power, and metallics stop really well but provide less modulation, then hopefully the semi-metallic Galfers will fall right between the two. And with any luck, they'll do so without much howling.

    I'll report back in a week or so with results.

  7. #7
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    If I remember right the galfers are only marginally louder (if at all) than the resin shimanos, noise really shouldn't be an issue.

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