First brake caliper rebuild and some questions...

Discussion in 'Tech' started by duc995, Jul 3, 2018.

  1. duc995

    duc995 Well-Known Member

    Rebuilding the two-piece front calipers on my ‘12 zx6r, and my first time doing this. So far i’ve gotten everything disassembled without issue and before putting the new parts in I was wondering about the fluids seals and their orientation. I’ve inspected the old and new parts under magnification and I don’t see any markings on either the dust or fluid seal. The service manual makes no comment about this, however, some YouTube videos talk about the fluid seals being cut in such a way that they have to be oriented correctly. What is the truth of the matter?

    Second, the caliper pistons seem to have a coating on them, like high-end fork tubes, and i’m assuming that the two pistons where I can see the coating is either dull, or gone, means I need to replace those pistons? There is no corrosion, just a loss of coating so I don’t think it can be cleaned/buffed out.

    Thanks for any guidance....

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  2. Banditracer

    Banditracer Dogs - because people suck

    I've rebuilt alot of calipers and have never seen where there was a orientation for the seals. For what ever that's worth.
     
  3. duc995

    duc995 Well-Known Member

    It’s worth a lot. Thank you for helping.
     
  4. MurfSVR

    MurfSVR Well-Known Member

    Orientation no but the order is important. Did you break the two halves of the caliper apart? I’ve read in service manuals that for rebuild service you don’t take those apart. Just like with my r6 calipers the service manual says to not remove the anodized/aluminum caps (even though I did before realizing my mistake).

    Regarding the piston coating I would take a light polish compound and microfiber cloth and clean them up. These pistons see a lot more heat than fork bushings but far less movement. By the book you should replace them but I wouldn’t unless there’s a ton of brake drag.

    Some tips:
    1) if you use Water or a degreaser to clean the calipers up before reassembly give them some extra time to 100% dry. Moisture is your brake systems enemy - i would only use brake parts cleaner which dries quickly.
    2) if your rebuild kit came with that red rubber grease - use it to put a minimal film on the seals but not enough to see chunks of it. Don’t get any of that stuff where the brake fluid sits behind the calipers. Many say to just use brake fluid so that’s an option too.

    3) Don’t forget to scrub away/remove the varnish and/or replace the pins/spring clips that hold the pads in place. No need to grease these pins that will only attract gunk and debris. If you bend a clip and just bend it back you may be fine but I would replace it.

    Hope this helps!


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  5. Issa Trad

    Issa Trad Member

    I've never used grease on the seals, always just used brake fluid to lube them up putting the pistons back in.
     
  6. duc995

    duc995 Well-Known Member

    Thanks for everyone’s help!

    Everything seemed to go smoothly, and I was actually able to polish and clean the marks from the caliper pistons too!

    My favorite part was when the three bolts I removed to split the calipers actually turned without damaging their heads. I have a twenty year old set of Brembo gold line calipers on my 916 with Allen head bolts that seem to be made from Swiss cheese! No way those are coming off intact....
     
  7. Banditracer

    Banditracer Dogs - because people suck

    :stupid:
     
  8. duc995

    duc995 Well-Known Member

    I am disappointed to find out that one of the reasons that I did this service - the caliper pistons were not moving symmetrically together - is normal. My pistons didn’t move symmetrically before the service (oem factory installed seals on a ‘12 zx6r) and now after replacing the seals with factory parts nothing has changed. So, all I can conclude is that the hype that the pistons need to move symmetrically or else it indicates a problem can NOT be trusted. I guess live and learn for me!
     
  9. MELK-MAN

    MELK-MAN Michelin.. Bitches..

    i have never seen pistons with no pressure pushing back against them, all move evenly. They need to move easily, and if you hold one the rest keep moving (even if one a bit faster than the rest), but all move at same time? don't think that happens. (could be wrong, but don't think so). Even on dirt bikes with 2 pistons on the front caliper, one moves a tad faster in most cases. ya clean em as best ya can though.
     
  10. duc995

    duc995 Well-Known Member

    Thank you. Good to know!
     
  11. ducnut

    ducnut Active Member

    I’m late to this party. On Honda VFR and F3 calipers (not sure on other models) there’s a definite orientation to seals. The inner is a tapered shape and the thicker side goes toward the fluid, so as one applies pressure, the pressure on the seal provides a tighter seal. If the seal is reversed, fluid can push through the taper and leak. The pic I have of a tapered seal is too big and don’t know how to resize stuff. Anyway, I just didn’t want someone to assume ALL caliper seals don’t have orientation.
     
  12. Pneumatico Delle Vittorie

    Pneumatico Delle Vittorie Retired "Tire" Guy

    I thought that was true with all caliper seals?
     
  13. ducnut

    ducnut Active Member

    It was stated otherwise, however many responses back.
     
  14. Spitz

    Spitz Well-Known Member


    If you mean a free floating piston compared to another they will likely never move together. The one with the least resistance is going to move. Unless you have some obvious resistance issues this is a non-issue. You should be able to push one piston into move another easily though.
     
  15. duc995

    duc995 Well-Known Member

    Yep. I watched a Dave Moss video on calipers and he said that if you apply the brake lever and all four pistons don’t move simultaneously, and the same amount, that the caliper seals need to be replaced. Now I know that he is incorrect.
     

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