DOT 3 compatible grease for caliper pistons?

Discussion in 'The Garage' started by Yakima, Apr 7, 2011.

  1. Yakima

    Yakima NC 700

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    I'm rebuilding my calipers (1985 Honda CB650SC) and usually install the pistons using brake fluid as lubricant. (Manual says DOT 3 or 4; I'm using 3 and am happy with it. Not interested in exploring the virtues of 4, 5.1 or 5)

    These pistons are very tight, and I've damaged a seal while pressing them in.

    I've read of using grease on the piston, a light, light, coating. But: what grease? Permetex makes something compatible with brake fluid. I tried it with an Amsoil all purpose grease I use for most everything: it dissolved into the fluid, turning the fluid pink. Not sure what it did to the fluid.
    I've drained everything. Got new seals. Ready to install, but don't want to damage any more seals.
    Grease recommendations? Other advice?
    Many thanks.
    #1
  2. JSharp

    JSharp Been here awhile

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    #2
  3. Bill the Bong

    Bill the Bong Supern00ba

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    Red rubber grease for hydraulic connections
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  4. Yakima

    Yakima NC 700

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    Great! Thanks, guys.:D
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  5. showkey

    showkey Long timer

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    If everything is right the piston should install with hand pressure.

    Remember the seal is the part that will cause the piston to retact after brake application, the piston must move smoothly in the bore or the brakes will drag or hang.
    #5
  6. Tosh Togo

    Tosh Togo Long timer

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    What he said. I've found that lubing the new seal with DOT-whatever before installing it into the caliper's bore helps a lot... apparently by being lubricated the seal can more easily move into its' slot, and let the piston slide by.

    Btw-use absolutely no "grease" of any kind, not even a little bit, unless it says that it's designed to be used in a hydraulic brake system...if it was made from oil, it can result in the seals in the brake cylinders swelling to the pont of sticking. :cry
    #6
  7. big-t

    big-t Been here awhile

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  8. Tepi

    Tepi Been here awhile

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    I use PBR Rubber grease, its made for brake rubbers. Then I also use a brake grease for the slidebushing if applicable, its made for that, ATE makes it.
    #8
  9. EduardoMas

    EduardoMas Spartan Overlander

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    Using brake fluid to lubricate the seal and dust seal before installation is all that is needed. The pots should press in by hand, unless you are still connected to the rest of the brake system (I am sure you are not).
    Lightly wet the perimeter of the pot before installing. If it does not press in with your fingers something is off. A larger section seal, a twisted seal, swapped seal for dust seal sound like possible culprits.
    My experience is only with XRR and KLR. I spec hundreds of seals, nothing in this size range needs much force to compress (even 28%) when lubricated.

    The caliper greases are for pins and items other than the piston seals. These greases and the brake fluids do not contact each other AFAIK.

    Cheers!

    Eduardo.
    #9
  10. hpsVFR

    hpsVFR Hoosier Daddy

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    Yes, to clean out accumulated grime, and to allow inspection and refurbishment or replacement of pistons and seals. Refurbishment generally amounts to a good washing/cleaning, and the use of crocus cloth (a fine abrasive paper/cloth product) on your pistons, replacement of seals (you've got them out anyway, and they're cheap), and perhaps attention to your bleed nipples (replace chewed up ones, swap speedbleeders (tm) in, seal the threads).

    You should do it often enough, that is, inspect your calipers and decide whether or not they look goopy/gunky enough that you're willing to empty the system of fluid and re-fill/flush it. This will happen much more often in environments where salt corrosion is an issue than in other environments, as I understand it.
    #10
  11. bwringer

    bwringer Gimpy, Yet Alacritous

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    I suspect you're trying to use an aftermarket kit. The aftermarket brake rebuild kits commonly sold for vintage bikes are nothing but dangerous low-rent junk. (I'm lookin' at YOU, K&L. :dood ) Shame on the retailers who peddle this evil crap.

    Get OEM parts from your favorite Honda parts source, and everything will go together like buttuh. And it will actually work properly afterwards. Plus, the OEM kits are a much better deal -- they usually include new pistons for close to the same price as the shoddy seal-only aftermarket kits.

    Do NOT contaminate your brake system with grease or anything else. Fresh brake fluid is all the lubricant you need. If you have to force anything, something is wrong.

    Many people in this thread are ignorant or aren't paying attention, and are recommending the "brake grease" that is used on the slide pins. This is VERY dangerous. Again, NEVER, EVER, EVER apply ANYTHING besides fresh, clean brake fluid to the innards of your brake system.
    #11
  12. Yakima

    Yakima NC 700

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    I'm cheap. Not frugal. Cheap.
    Ordered OEM caliper seals/dust seals. Two weeks ago. Should be in-hand tomorrow.:D
    I'll try assembling first using only brake fluid. Coat everything in that nasty stuff.
    Parts are CLEAN, new stainless lines are on, bike is running sweet (although she burns oil. Rings next winter, methinks.)
    Thanks, guys, for all the suggestions and advice.
    #12
  13. C Squared

    C Squared Now with TURBO!

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    Everything stated below :deal
    If it goes together tight, it will not work! (won't release)

    This info brought to you by an ASE certified person :D



    #13
  14. Yakima

    Yakima NC 700

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    Got all the pistons in. Three went in with MUCH pushing with fingers/thumb. The fourth required a tap with a hammer.
    I know, I know: should go in with hand pressure only.
    Uhn uh. didna happen.
    Once in, I mounted the calipers without pads. Filled and bled. Pumped the pistons out. Pushed them in. Installed pads.

    It was late when I finished. Torque things up today and perhaps go out this evening for a bit.
    Oops. Nope. Work tonight.

    Thanks for the help, one and all.
    #14
  15. chammyman

    chammyman Been here awhile

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    brake fluid only.

    Anyway out of interest where on earth can you find DOT 3 fluid? You'd need a time machine here. DOT 3 last sold probably 20 years ago here.
    #15
  16. C Squared

    C Squared Now with TURBO!

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    DOT 3 is still the norm here.... 4 is happening more and 5 is race...
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  17. Beezer

    Beezer Long timer

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    Parker O Ring Lube... that's what it's called. It's the slickest stuff on rubber ever. Made by Parker, the leading name in O ring things. I have used it on everything bike, auto & aircraft with no problems. Great stuff.
    #17
  18. simonpig

    simonpig droppin' jewels

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    I am rebuilding the front brake caliper on an XT225. I ordered the Yamaha OEM front brake rebuild kit (includes both pistons, 4 seals) and it came with a little packet of pink grease. Nowhere in the rebuild manual does it state to grease anything and as mention before, I was only planning on using the brake fluid to lubricate it.

    What is Yamaha trying to tell me by including a packet of this pink grease?
    #18
  19. H96669

    H96669 A proud pragmatist.

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    They may be trying to tell you that leaving brake fluid residues outside of the seal may not be such a good idea.It will attract moisture and may cause corrosion later on. Use the grease and use some on the external dust seal if you have one of them.

    Parker O-ring lube....right on their product specs it says that it shouldn't be used in brake applications. I just got a big can of Miller Red grease from the UK, cheap and have already been portioning out for some friends that also understand brake rebuilds and other rubber parts preservation.

    [​IMG]
    #19
  20. simonpig

    simonpig droppin' jewels

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    Thanks for the response, that makes a lot of sense about lubing the outer exposed seal with the grease.
    #20