Brake caliper piston - Renault R8 Gordini - Page 2
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Thread: Brake caliper piston - Renault R8 Gordini

  1. #26
    1000+ Posts renault8&10's Avatar
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    I’ve heard the same as Frans - the embossing describes which seal should be used, round/circle = round seal; square seals = triangle embossing. My guess is it may be different suppliers to Renault. People do say that one lot of seals and calipers are interchangeable, but not the other way around. That might be why someone will say they used a round seal in a square profile for example, but someone else will go the other way around and it didn’t work.

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  2. #27
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    Frans, I think you are quite correct. Those marks are what I have always thought show you which seal to use. I've used square seals exclusively for some time but maybe I have diamond-shaped marks on all the callipers - that's embarassing from my side! So, like you, I don't think I've stuck to it either.....

    Talking to Geckoeng over the weekend, it seems that some combinations don't work, and when assembling the ones that don't work you don't feel much resistance when pressing the piston in (by hand of course). I also have a memory from the 1970s of very early R8 callipers having a different size 'o' ring. Julian's experience seems to be the same - I've never had that complete failure to seal myself.

    Thanks!
    JohnW

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  3. #28
    Ove
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    Hello,

    there were three generations of these calipers, all made by Bendix.
    First one with round seal and 8mm axle,
    2nd one with round seal and 9mm axle and
    3rd one with square seal and 9mm axle

    I’ve noticed the same as Frans and JohnW.

    Cheers

    Ove
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  4. #29
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    Are there any differences in the casing internally regarding round or square seal? Have to refurbish a set of front calipers as well. These had a square seal, but I have a hard time seeing if the indent at the front is diamond or round. Can you identify this with a parts number? Or did these calipers have the same parts number regardless of version?

  5. #30
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    I can't see any difference between "round" and "square" callipers. It's hard to measure that groove accurately, at least with what I have.

    If you go back up the thread, you'll see that we're all a bit confused but mostly haven't had trouble using difference seals. However, the ones that have failed (and we don't know what exact combinations are affected) leaked immediately and seem to have had no resistance to pushing the piston (by hand please!) past the seal. That might mean that it if is tight it seals...… I decided years ago that I preferred the square seals and haven't had a problem.
    JohnW

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    Ok, thank you. I will try square seals then and see how it goes.

  7. #32
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    I'm late to this party, but I remembered I'd read ages ago that square section seals also have the benefit of causing a slight retraction of the piston too, by flexing and returning (as in the attached pic) so reducing friction.

    square seals.jpg
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  8. #33
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    Quote Originally Posted by Stuey View Post
    I'm late to this party, but I remembered I'd read ages ago that square section seals also have the benefit of causing a slight retraction of the piston too, by flexing and returning (as in the attached pic) so reducing friction.

    square seals.jpg
    Where DID you find that diagram? I've never seen it. I've never really sorted out, to my satisfaction, the difference between the callipers marked for round vs square seals. Still, it's a great anorak conversation that just gives and gives...
    JohnW

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  9. #34
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    There is a lot to R8 brakes. This is slightly OT as they are not from a Gordini. They may be familiar to some but I had not seen them before...

    FB_IMG_1551777354778.jpgFB_IMG_1551777360759.jpgFB_IMG_1551777370826.jpg

  10. #35
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    Quote Originally Posted by JohnW View Post

    Personally, and there are opinions about this too, I use Silicone brake fluid (Dot 5) because the corrosion behind the 'o' ring is caused, in my view and the opinion of others, by moisture in the hygroscopic conventional brake fluids. I've used this expensive fluid for nearly 3 decades now and have had NO problems, but that's just personal experience not a recommendation.

    Enough from me.....
    Are there anything I need to think about if using Dot5 brake fluid? I see that it is not mixable with other brake fluids. Calipers will have new seals, brake lines and brake hoses are new, master cylinder and hydraulic handbrake have old seals though.

    Do Dot5 fluid help regarding leaks through caliper seals? Tried to remove any dirt and pitting in the seal groove.

  11. #36
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    Quote Originally Posted by ReidarUF View Post
    There is a lot to R8 brakes. This is slightly OT as they are not from a Gordini. They may be familiar to some but I had not seen them before...

    FB_IMG_1551777354778.jpgFB_IMG_1551777360759.jpgFB_IMG_1551777370826.jpg
    ReidarUF,
    I think the caliper you show in the pictures are the last of the R10 type and were the ones sold as replacement parts. I had 2 of the last R10 made in ZA and they had those calipers on them. But we never had those as replacement parts, only the earlier model.

    Ray
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  12. #37
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    I've never seen those calipers without a nut at the back but the new replacements from Mecaparts are like that too.

    Re Dot5, I've been using it for years (29 years in the 4CV and about 5 in the R8) as have a few of us in WA. Good results. My argument for the R8/10 is that because Dot5 isn't hygroscopic (it is silicone fluid) the corrosion that is common with the normal hygroscopic fluids behind the 'o' ring seal should not occur. I think that even fluid changes won't help this problem as the water will be absorbed exactly at the meeting point between fluid and air, that is AT the seal and a fluid change won't change this or remove the water from the contact zone between seal and caliper body.

    My two bob's worth anyway....
    JohnW

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  13. #38
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    @Ray: Those calippers being sold as replacement parts may explain it. The picture were sent to me from the Dutch owner of a FASA R8 he had just imported. It had this type on one side only so he was a bit frustrated. The car actually had drum rear brakes. To bring down the price i guess.

  14. #39
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    correct Frans never failed me in 40+years.so simple
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  15. #40
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    I'm reading this with interest as I'm about to do the same on mine.

    Quick question but.
    Are G and standard 8/10 the same calipers?

    Mines a 70 model 8G and would the calipers be the same as a 70 R10?

    Just wondering if I'm going to be in the same megapart boat or can I just raid my brothers collection of standard 10 parts.
    David Cavanagh

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  16. #41
    1000+ Posts Frans's Avatar
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    Hi David,

    The calipers are all the same, only change that I know of is the slightly thicker rotors used on the G, the opened up backing plate with the air scoop and the booster.

    Frans.
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  17. #42
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    At least early R8 and Floride S also had air scoops on the backing plate, no booster or thicker discs though.

  18. #43
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    Quote Originally Posted by Frans View Post
    Hi David,

    The calipers are all the same, only change that I know of is the slightly thicker rotors used on the G, the opened up backing plate with the air scoop and the booster.

    Frans.
    Thanks Frans,

    Yes I've got new thicker rotors on order because I can't steal Steves.

    All good thanks.
    David Cavanagh

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