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  1. #1
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    Master Cylinder Question!!!

    Quick Question,

    Are the master cylinder "springs" coated with a light oil soluble grease by manufacturer's to give it a smooth return (similar to fork springs but in a very minute quantity)...wouldn't this alleged grease be deemed potential harmful as it could penetrate in certain of the brake's cavities causing a potential sludge it up?

  2. #2
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    They don't need to use grease to lubricate the return springs because the DOT fluid does that job, as it does at every moving point with the sealed system: it lubricates all of the piston seals, too. Hope use a silicone grease in the assembly process to facilitate seal and pistons fitting, but the quantities are so small that one would be hard pushed to find any trace of them after a few miles on the brake. In all my time servicing Hope brakes I heve never found one to be negatively affected by the factory grease.

    Are you asking because you have a specific problem?
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  3. #3
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    Quote Originally Posted by SteveUK
    They don't need to use grease to lubricate the return springs because the DOT fluid does that job, as it does at every moving point with the sealed system: it lubricates all of the piston seals, too. Hope use a silicone grease in the assembly process to facilitate seal and pistons fitting, but the quantities are so small that one would be hard pushed to find any trace of them after a few miles on the brake. In all my time servicing Hope brakes I heve never found one to be negatively affected by the factory grease.

    Are you asking because you have a specific problem?
    just wondering since i had some oil soluble rock shox grease for my fork...and wanted to know if a slight application on the spring of my brakes would ease the spring return or gunk it up

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    I'd say that that would be a no-go, although you could call your brake manufacturer and see what they say. However, as I said, it's the lubrication at the point where the seals meet the piston bore that influences the smoothness of the lever return, rather than the actual spring itself, and this lubrication is provided by the brake fluid.
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  5. #5
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    Quote Originally Posted by SteveUK
    I'd say that that would be a no-go, although you could call your brake manufacturer and see what they say. However, as I said, it's the lubrication at the point where the seals meet the piston bore that influences the smoothness of the lever return, rather than the actual spring itself, and this lubrication is provided by the brake fluid.
    cool understood...when you reinstall your pistons do you lube similar to what you told em hope does?

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    Caliper piston seals get DOT fluid dripped into the seal seat, then soaked again when the pistons are pushed back in. For the lever, I again use DOT to coat the two seals on the piston and also to wet the inside of the piston bore.
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    great so its:
    Lube [DOT fluid] on the 2 MC spring seals
    Lube [DOT fluid] on the seal seat + on the piston [thus lubing the outer and inner parts of the seal]

    but as i asked on your site, you mentioned adding dot fluid when you put the bore caps in...but that was after already having put the seals + pistons...that was my question, what exactly are you lubbing once you put the bore caps on

    also, I would assume you put Teflon tape on the fittings...some would say for the good ridge lines, not Teflon is required...but for the regular kevlar, i would Teflon the threaded intersections of the fitting.... i know that I always remove the bleed screw and Teflon it [making sure i dont Teflon over the bleed hole on the inside]

    How do you do you setup? should I Teflon as much as I said...less...more?....and how come you know soo much about brakes anyways...seems like you've been working on them for quite some time

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    I feel like I'm dealing with you in triplicate today, George!!

    For the benefit of those who don't/haven't reading our communications on my maintenance pages, the lubing of the bore cap seals on Hope Mono calipers is simply to soften the seals to help encourage a better seal. A soft seal will adapt its surface to match the relief of the surface it mates to, whereas a hard seal is less likely to, thus allowing small spaces for air to be pulled in through.

    I've never found any need for Teflon tape on fitting because the threads are so precise and because the compressible brass olive on either end of the hose ensures that the fittings all close up well together, providing a seal capable of withstanding the high pressure of a braking system. The bleed nipple will relatively large threads given the size of the component, whaich again allows for enough torque to be used to seal the joint. If you're needing to add Teflon tape to any threads to keep a seal, then I would suggest that you should be replacing those fittings.
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