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Thread: JDM ADM front caliper seals

  1. #1
    Member grey_nomad's Avatar
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    Default JDM ADM front caliper seals

    I rebuilt a set of JDM calipers using the better condition pistons that came out of the original ADM calipers. Measured both with micrometer and as far as I could tell they were the same size.

    I fitted a PBR seal kit from the local brake shop to the JDM calipers using the ADM pistons and now I find brake fluid weeping from the seal area. Brakes work fine but there's a definite weep of fluid.

    Should I have used a genuine kit? Some other seal kit?

    Can the ADM pistons be used in the JDM calipers?

  2. #2
    Veteran lolwat's Avatar
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    did you lube the seals, with eaither brake grease, or some brake fluid it self??

  3. #3
    Member grey_nomad's Avatar
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    Yep, with brake rubber seal grease.

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    Veteran Jonny Rochester's Avatar
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    Then I have a brake piston out, I pollish it up with a wire wheel on the bench grinder. It is hard chromed, and you won't hurt it with the wire wheel. But it's good to take off all the old crap that builds up. Maybe some of this crusty stuff cut the new seal?

    If would seam you have to take the piston out and do it all again.

    Also, try and clean up inside the caliper as much as you can before the new seal goes in. And smother the piston with rubber grease.

  5. #5
    Member grey_nomad's Avatar
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    Did all that. I am a retired motor technician and have rebuilt countless calipers and have never had this particular problem. Hence my question about piston sizes and seal kits.

    Just looking for confirmation of the piston sizes between the ADM and JDM calipers. If they are identical, then its a sealing problem. And it is happening on both left and right calipers, so it is something common.

    Think I'll grab the genuine Toyota kits from AJPS and redo them.

  6. #6
    Veteran Jonny Rochester's Avatar
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    I know PBR clutch masters always leak just a little. I'm not a fan of PBR.

  7. #7
    Veteran LittleRedSpirit's Avatar
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    Just while were on this topic, does anyone have the front and rear piston diameters for ae86 disc brakes? I need this info to do some maths on a possible brake upgrade.

  8. #8
    Veteran timbo's Avatar
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    i have some rears lying around in the lockup, so i will have to wait until a weekday before i can have a look.

  9. #9
    Veteran Jonny Rochester's Avatar
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    Front brake pistons are 50.8mm
    Rear brake pistons (for disc) are 34.93mm

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