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  1. #1
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    Mechanic question: New to Formulas, miss my Shimanos!

    Please help with some advice - would be great to know if I'm just missing out on an obvious method to separate the pistons.

    I just replaced my first set of pads on my Formula RX brakes (2012). The rotor won't fit between the pads when I try to put the wheel back. OK, no sweat, think I. With my shimanos I would just take a wrench and push the pistons apart one by one, pop the pads back in, and it would recenter automatically and easily.

    With these Formulas, I try to push one piston out, and the other pushes in. So, what's my method here? The bike didn't come with a piston separator tool or anything.

    Does this mean I need to bleed the brakes? They still feel totally strong, not squishy at all.

    (The front brake, same situation, will accept the rotor, but even with careful skip-tightening can't get it in without rubbing. Is there a different way I should be going about centering the brakes too?)

    Thanks for any thoughts!

  2. #2
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    But they worked OK with the older pads even when the brakes were new? I don't think the brakes need bleeding on the contrary, it sounds like there's too much oil in the system but that again is probably not the case here. Hmm which brand are the new pads? Maybe there's just "too much meat" aka braking material on the new discs and it needs to be sanded off. I've had this problem with one of my brakes (not Formulas) and I needed to manually sand the pads to even fit the rotor in between.

    But then again maybe it's a formula specific issue... and I wouldn't know nothing about that since I never owned Formulas.

  3. #3
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    Was fitting some new pads in a pair of Avid Juicy's and the rear caliper had the same symptom, plus was recently bled and didn't fancy doing it if not required. So what I did was loosen the caliper bleed port screw a little (not too much otherwise you'll let air in) then pushed both the pistons back. A little excess brake fluid weeped out the bleed port. Then retighten screw, fit pads, yadda yadda yadda. Pump brake lever a few times to recentralise everything and bed-in pads. Worked for me. YMMV.

  4. #4
    dru
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    Quote Originally Posted by StanleyJ View Post
    So what I did was loosen the caliper bleed port screw a little (not too much otherwise you'll let air in) then pushed both the pistons back.
    Don't do this.

    Only because you don't need to.

    When this happens you can push them both back by shoving some more metal bewteen the pistons. (I don't like doing this, but shove them back with the pads in place, only because they are much cheaper to replace)...

    Most often I've used just a chisel that I then twist, but also shoved a chisel and a knife in between to push them both back.

    Drew
    occasional cyclist

  5. #5
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    Quote Originally Posted by dru View Post
    Don't do this.

    Only because you don't need to.

    When this happens you can push them both back by shoving some more metal bewteen the pistons. (I don't like doing this, but shove them back with the pads in place, only because they are much cheaper to replace)...

    Most often I've used just a chisel that I then twist, but also shoved a chisel and a knife in between to push them both back.

    Drew
    In my case, I tried this already and yes it did get the pistons back some of the way. So yes your step should be tried first. No amount of brute force would compress excess fluid once all the "free space" in the system was taken up after this step though, so in my case, had to bleed some fluid out. As I said, YMMV.

  6. #6
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    Mike did you try to bleed a little fluid out? I'm curious of the out come. I suspect my front RX has too much fluid from the factory bleed. there is very little pad clearance (can't get it to not rub) and the pad contact it further out than the rear.

    Stanley, how much fluid did you remove? a couple of drops?
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  7. #7
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    Quote Originally Posted by Widgeontrail View Post
    Stanley, how much fluid did you remove? a couple of drops?
    Wrapped a bit of paper towel around the caliper covering the slightly loosened bleed port screw... so no idea exactly. Not much more than that as it was just to get the pistons in my uncooperative Avids to settle in that last bit of a millimeter.

  8. #8
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    Haven't gotten around to this - in fact I don't even have a bleed kit yet

    Quote Originally Posted by Widgeontrail View Post
    Mike did you try to bleed a little fluid out? I'm curious of the out come. I suspect my front RX has too much fluid from the factory bleed. there is very little pad clearance (can't get it to not rub) and the pad contact it further out than the rear.

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