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  1. #1
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    New SRAM hydro problem – rotor hits pad spring

    ANSWER: it was the brake pad spring. The one that came with the new bike was too narrow at the top and too loose as a spring. It didn't press the pads back far enough, making it almost impossible to center the caliper on the rotor. And even when the caliper was centered, it would slide down and hit the rotor directly.

    I got a new set of SRAM pads and the spring in that kit was subtly but significantly different: it didn't narrow above the pads the way the original did, and it had FAR more spring. Put the new pads in and it was immediately obvious that I had way more room to center the caliper. On the old spring the spring would slide up and down above and below the pads. On the new spring, the pads and spring float together as one unit, and the rotor never hits the spring.

    Note: with the proper spring, the shimano rotors seem to work just fine.


    –––original post below.

    Just got N+1 from Bikesdirect, a whipshot Ti with SRAM Force 1 hydraulic.

    Set up the RD, no problem, replaced the 6-bolt rotors with centerlock (the bike came with wheels with center lock hubs) and everything else seems fine.

    I can center the calipers on the rotors with no rub, but the rotors hit the brake pad spring (between the pads).

    If I pull the spring up and out of the way, the rotors spin freely with no rub, but if I push on the top of the clip just a bit – or if, on the road, I hit a bump – the top of the rotor rubs the spring badly.

    I'm at a loss on this one. I guess I could try to shim both calipers, but that seems like quite a kludge, and shouldn't be necessary on a new bike (even if it is from BD).

    Both the calipers are set up for 160mm rotors; the bike came with 160mm rotors and the replacements I used are 160.

    ANY IDEAS?
    Last edited by fronesis; 3 Weeks Ago at 01:53 PM.

  2. #2
    'brifter' is a lame word.
    Reputation: cxwrench's Avatar
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    I have had rotors replaced under warranty for this and I've sanded/filed the slight roughness you sometimes get on the edges of the rotor.
    I work for some bike racers
    I've got some bikes, some guns,
    and a bunch of skateboards

  3. #3
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    Thanks for the reply, cxwrench. In this case, though, I don't really think anything is wrong with the rotors, as they are literally brand new shimano icetech – they are true and look fine. So I'm not sure that getting another new set would change anything.

    I found someone on the mt bike forum who seemed to have just this problem:
    I had a combo of sram caliper spacer/shimano icetech rotor/m8000 brake caliper that had that [was] in the stand or on smooth/flat terrain. Point it downhill and on the big bumps, i got the sound of the rotor hitting something. Turns out the rotor was bottoming out inside the caliper as the spacer was too small by a mm or two.
    He seems be blaming the problem on the pad spacer spring itself. But unfortunately he doesn't say what he did to fix the problem.

    Follow-up: I removed the pads and return spring and tried bending the return spring slightly so that it there was a bit more room. Maybe that helped a little, but the main problem is that the entire return spring is quite loose – any big bump and it shifts down and will hit the rotor.

    On Shimano hydraulic the return spring is held in place by the retaining bolt, but on SRAM, that bolt goes through the pads but not the spring – so the spring is just there to bounce around.

    Maybe my return springs were messed up to begin with and I need to try a new pair.


    ​That's my best guess for the moment.
    Last edited by fronesis; 3 Weeks Ago at 09:50 PM.

  4. #4
    RoadBikeReview Member
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    May I ask why you put Shimano rotors in a SRAM system?
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  5. #5
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    Quote Originally Posted by Lombard View Post
    May I ask why you put Shimano rotors in a SRAM system?
    Sure.

    The Shimano rotors were available and priced fairly at my LBS.

    I did some quick searching and quickly found a dozen different message threads where people said SRAM and shimano rotors (of the same size) were easily interchangeable.

    I had tried setting up this bike with the original SRAM 6-bolt rotors (adapted to the center lock hubs) and I found it IMPOSSIBLE to even come close to getting the rotor not to rub the pads. It was actually easier to set up once I got the shimano center lock rotors installed.

    It’s possible, of course, that the rotor is the problem. But I really can’t see how.

    Right now I have the caliper perfectly centered with absolutely no rub on the pads. The problem seems to be the retaining spring, which bounces around a lot.

    I’m also wondering at this stage if the hydraulic fluid was overfilled.
    Compared to my two shimano hydro bikes, there is simply much less clearance between the pads and rotors on this bike. I read a thread elsewhere where someone was having similar problems to mine, and found that the system was both overfilled and filled with air. Given all the other shortcuts that BD took, there’s no reason to think they followed the SRAM bleeding instructions.
    Last edited by fronesis; 3 Weeks Ago at 08:17 AM.

  6. #6
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    Follow-up: Lombard had a good point, and I probably shouldn't believe everything I read on the internet.

    The SRAM 160mm rotors actually measure more like 158mm.

    The Shimanos measure exactly 160mm.

    On the Shimanos, the top high point on the brake pad is grabbing the rotor below the outside edge of the rotor. So I've got some rotor sticking up above the brake pads, and whatever else might be wrong with my system, this is clearly causing problems.

    I'll need to get new SRAM centerlock rotors.
    And then I may or may not need to bleed the system and replace my bad retaining springs.

    This bike is going to end up having more time in it than a complete build from scratch.

  7. #7
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    well glad you figured this out!
    Mixing components of tight tolerances,... this sort of stuff is not unsurprising to me.

  8. #8
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    Quote Originally Posted by aclinjury View Post
    well glad you figured this out!
    Mixing components of tight tolerances,... this sort of stuff is not unsurprising to me.
    Just in case anyone reads this thread in the future: the Shimano rotors were NOT the problem in any way. I’ve got 3 test rides on the bike now, and the shimano rotors work perfectly with the SRAM calipers.

    My problem was a bizarre one, but the issue was solely that I had the WRONG brake pad spring. But this incorrect spring came with the brand new SRAM calipers and brake pads (on a brand new bike). I’m pretty sure it’s a SRAM spring, but I suspect it’s for a different set of brake pads (probably for mountain bike calipers). I can only guess that the bikesdirect people just threw in the wrong spring.

  9. #9
    RoadBikeReview Member
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    Quote Originally Posted by fronesis View Post
    Follow-up: Lombard had a good point, and I probably shouldn't believe everything I read on the internet.
    Sometimes I get it right, sometimes I get it wrong. This time I got it wrong.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  10. #10
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    OP: thanks for posting the conclusion at the top of the thread. Glad you got it sorted out.

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