Brake caliper- round or square seal.
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  1. #1
    Fellow Frogger! Paul T's Avatar
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    Default Brake caliper- round or square seal.

    Hi all,
    I am in the process of rebuilding the brake calipers on the R8G and would like some info about the caliper seals. I have rebuilt R8/10 calipers years ago but memory does not serve well anymore.

    There are two types available being the typical "O" ring type which is a round section or the square section. My front calipers have the round type seal and the rear have the square section seal. The calipers are all machined to take the square seal.
    The round seal appears to be a loose fit in the groove where the square seal is a tight fit.

    What is the difference between the seals and what would be best to install?

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    Thanks,
    Paul.

    Paul Tomlinson
    R1135 Gordini 1968.
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    Hi Paul,

    My memory is fuzzy too.
    I think if you look carefully at the calliper in line with the middle rib and in the Y of the "fingers"
    you will find a small marker in the casting.
    Two concentric circles signifies round seals,
    or a circle within a square means square seals.
    The machining for both types within the calliper bore is square either way.

    Hope this helps..

    Steve

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    IF the calipers are all machined to take the square seal then the square seal it is. The square seal is always a tight fit.

    There are some traps for young players on reassembly re aligning the gap in the self adjuster circlip and the drilling on the front face of the piston. I posted a longish piece on this pre the crash.

    All I could find is this.

    http://www.aussiefrogs.com/forum/showthread.php?t=85805&highlight=caliper


    PM me if you need more info.

    All the best

    P
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    Pretty sure this stuff is in the manual no? - As in the last time I did it I had instructions...

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    My Floride S which is pretty original actually had round seals and marks for round seals. I was always of the opinion that the early cars Floride S and R1130 R8 had square. But it appears as if that isn't the case. I will say that the dimple that is supposed to be on the piston to indicate that it should be upwards did not exist on The Floride S but a very very faint mark probably scribed with an electric pencil of the 60's, But it did take a lot of finding. The R1130 workshop manual refers to this mark as an "electroscribed mark". In the parts book they refer to two part numbers for both kits and calipers R1130 No. 1 to 285525 (a) and 285526 (b) on ward so whether that indicates square and round caliper seals I don't know. The early R1130 workshop manual makes no mention of either round or square seals. I do have calipers with the square mark but don't know which car they may have come from.

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    Quote Originally Posted by Sunroof View Post
    My Floride S which is pretty original actually had round seals and marks for round seals. I was always of the opinion that the early cars Floride S and R1130 R8 had square. But it appears as if that isn't the case. I will say that the dimple that is supposed to be on the piston to indicate that it should be upwards did not exist on The Floride S but a very very faint mark probably scribed with an electric pencil of the 60's, But it did take a lot of finding. The R1130 workshop manual refers to this mark as an "electroscribed mark". In the parts book they refer to two part numbers for both kits and calipers R1130 No. 1 to 285525 (a) and 285526 (b) on ward so whether that indicates square and round caliper seals I don't know. The early R1130 workshop manual makes no mention of either round or square seals. I do have calipers with the square mark but don't know which car they may have come from.
    Yup, all familiar territory!

    Apart from the usual traps with getting the piston marks aligned with the bleed screw (and the inner circlip gap right, although why you'd dismantle it is another matter).

    The very early R1130s were different from all the later callipers AFAIK and that might explain the two part numbers in the R1130 manual. However, to the best of my knowledge, regardless of the marks on the caliper which tell you whether round or square seals were fitted, both seal shapes seal OK in either type of later calliper. I wouldn't mix seal types from side to side though. I sweated over this issue some years ago, but all the kits seemed to have square seals, so I used them regardless of calliper markings and have had no problems.

    As a side issue, I changed to silicone fluid too. I now have the lightest, nicest brakes ever on the R8 - all to do with piston lubrication and cleanliness and no corrosion products gumming up the piston in the calliper.
    JohnW

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    Quote Originally Posted by Steve K View Post
    Hi Paul,

    My memory is fuzzy too.
    I think if you look carefully at the calliper in line with the middle rib and in the Y of the "fingers"
    you will find a small marker in the casting.
    Two concentric circles signifies round seals,
    or a circle within a square means square seals.
    The machining for both types within the calliper bore is square either way.

    Hope this helps..

    Steve
    Hi guy's,
    Just got home from work (midnight) and read your reply's. Just checked my calipers and they all have the square mark with one circle so that should mean square seals, thanks.

    I did note (as I sand blasted the outside of the calipers) the ones off the Gordini have the following marks on the backs-
    G
    67

    The one from my parts bin has-
    M
    67

    I'm thinking that the "G" might stand for- Gordini and "67"- manufactured in 1967? No clue what the M might stand for but they all look the same to me. And then again the markings might mean nothing at all.

    Thanks for the advise, its much appreciated.
    Paul.

    Paul Tomlinson
    R1135 Gordini 1968.
    Jaguar XJ-C V12 1975.
    Alpine GTA- ATMO 1987.
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    Quote Originally Posted by Paul T View Post
    Hi guy's,
    Just got home from work (midnight) and read your reply's. Just checked my calipers and they all have the square mark with one circle so that should mean square seals, thanks.

    I did note (as I sand blasted the outside of the calipers) the ones off the Gordini have the following marks on the backs-
    G
    67

    The one from my parts bin has-
    M
    67

    I'm thinking that the "G" might stand for- Gordini and "67"- manufactured in 1967? No clue what the M might stand for but they all look the same to me. And then again the markings might mean nothing at all.

    Thanks for the advise, its much appreciated.
    Paul.
    You can use the standard square seals with confidence then. I'd suspect those letters are casting marks of some sort - Simon might know better though.

    I'm not aware of the callipers used on the R8 Gordini being different from standard. Then again, G for Gordini and M for Major does make sense, but perhaps a coincidence.
    JohnW

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  9. #9
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    Could it be some sort of code for the month they were manufactured?
    what month starts with G in french (any)? M could be march or may; or it may be A=Jan etc

    My other guess would have been G= gauche (left) but then M doesn't equal Droit (right)
    KB


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    Quote Originally Posted by Paul T View Post
    Hi guy's,
    Just got home from work (midnight) and read your reply's. Just checked my calipers and they all have the square mark with one circle so that should mean square seals, thanks.

    I did note (as I sand blasted the outside of the calipers) the ones off the Gordini have the following marks on the backs-
    G
    67

    The one from my parts bin has-
    M
    67

    I'm thinking that the "G" might stand for- Gordini and "67"- manufactured in 1967? No clue what the M might stand for but they all look the same to me. And then again the markings might mean nothing at all.

    Thanks for the advise, its much appreciated.
    Paul.
    The rear calipers are marked-
    N
    67

    And a rear from the parts bin has-
    C
    68

    I'm pretty sure the numerals refer to the year of manufacture. The letter most likely stand for the month with A= January, B= February perhaps.

    Paul.

    Paul Tomlinson
    R1135 Gordini 1968.
    Jaguar XJ-C V12 1975.
    Alpine GTA- ATMO 1987.
    Jaguar X Type 2002.

  11. #11
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    Default brake caliper round or sqaure seal

    Just checked my R8 calpers, I have rebuilt mine ..definately sqaure seal type (front) and the numbers are different on each caliper A70 and M69. these are both from a 10 S. cheers Brian T

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    Default Brake Fluid

    Hi John

    I noticed your comment "As a side issue, I changed to silicone fluid too. I now have the lightest, nicest brakes ever on the R8 - all to do with piston lubrication and cleanliness and no corrosion products gumming up the piston in the calliper.

    Could you expand on the use of Silicone fluid, is it fully interchangeable with the normal hydraulic fluid eg. Castrol etc. or is it a total flush out job, and then, what about the plunger seal in the Master Cylinder etc. does it have any perishing effects??

    Be interested to know as I'm about to change to a brand new R8 master cylinder and do all the caliper piston seals as well.

    Thanks mate

    Phil

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    Quote Originally Posted by R8philSA View Post
    Hi John

    I noticed your comment "As a side issue, I changed to silicone fluid too. I now have the lightest, nicest brakes ever on the R8 - all to do with piston lubrication and cleanliness and no corrosion products gumming up the piston in the calliper.

    Could you expand on the use of Silicone fluid, is it fully interchangeable with the normal hydraulic fluid eg. Castrol etc. or is it a total flush out job, and then, what about the plunger seal in the Master Cylinder etc. does it have any perishing effects??

    Be interested to know as I'm about to change to a brand new R8 master cylinder and do all the caliper piston seals as well.

    Thanks mate

    Phil
    Hi Phil,

    AFAIK it is a "fully change rubber parts" job. I have done it twice now, on the 4CV and on the R8 and both times I coordinated it with a serious brake overhaul.

    So all wheel cylinders/callipers were cleaned, polished and resealed, and I fitted a new master cylinder kit and new hoses. With the R8 I finally threw the pressure limiting valve away and replaced it with a simple tee-piece (there's a thread on this somewhere). I think, but don't know for sure, that if you washed out hoses with meths and really got rid of the older fluid it might be fine but hell, new hoses aren't a bad idea!

    The 4CV brakes weren't touched for 18 years after putting in silicone fluid in 1990, until I replaced front wheel seals and a master cylinder kit. In that time I didn't touch the brake fluid once and didn't need to.

    I keep fluid from bleeding and filter it for re-use. Again no problems encountered re-using this fluid.

    I wrote this up in an article in Fourword a couple of years ago I think.

    Now, traps!

    1. The silicone fluid is prone to entrapment of fine bubbles and therefore, if aerated by careless handling and rough pouring, it may be hard to get a good "pedal" (my R8 is a little squishy and I intend to rebleed sometime).

    2. Things must be really DRY as water will sit in the bottom of wherever it is and may corrode things.

    3. Silicone fluid seems harder to seal (heaven knows why) so use new copper washers and really get things right at the wheel seals.

    4. Remember to flush meths through all the rigid pipework and the reservoir. It dries out Over a day or so or you can blow air through.

    Given the issues with corrosion behind calliper seals, I'd never use anything else but silicone fluid again.

    Cheers
    Last edited by JohnW; 29th June 2012 at 07:51 PM. Reason: Remembered something!
    JohnW

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    Thanks again John

    Hmmm! Might stick with the normal fluid for the time being, I'm sure a full set of new piston seals, new Master Cylinder and new pads right through will bring her up to better stoping from the 48 year old unknow brakes and milkshake consistency brake fluid I have at the moment.

    Thanks again, much appreciated.

    Cheers

    phil

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    Quote Originally Posted by R8philSA View Post
    Thanks again John

    Hmmm! Might stick with the normal fluid for the time being, I'm sure a full set of new piston seals, new Master Cylinder and new pads right through will bring her up to better stoping from the 48 year old unknow brakes and milkshake consistency brake fluid I have at the moment.

    Thanks again, much appreciated.

    Cheers

    phil
    Hi Phil,

    If you do the master cylinder and callipers, it is only 4 more things to unfasten to put new hoses on it. The only other thing I replaced is that pressure limiting valve.

    This is the perfect opportunity if you are ever going that way. Not that standard fluid isn't perfectly adequate. I found it worth the extra effort, but that's just me.

    Either way, good luck with the callipers - clean extremely well in the grooves behind the sealing rings. You'll likely find white powder and pit corrosion in there, but rubbing with folded fine wet and dry can smooth things enough to get sealing.
    JohnW

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    A bit of brake caliper seal theory.
    The square O rings are designed to "roll" with the piston under pressure. With pressure off the seal will roll back with the piston.
    This allows the piston to maintain a clearance [miniscule] from the pad.

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    Quote Originally Posted by Wildebeest View Post
    A bit of brake caliper seal theory.
    The square O rings are designed to "roll" with the piston under pressure. With pressure off the seal will roll back with the piston.
    This allows the piston to maintain a clearance [miniscule] from the pad.
    Thanks Wildebeeste.

    There is a friction-based adjustment take-up mechanism inside the pistons on these too, and I guess the square seals do the job of pulling the piston back a tad a bit better than round ones, as Renault changed from round to square during the R10 model run. Early cars were at times plagued by groaning noises from the rear brakes (four wheel discs of course) and a mixture of pads not pulling back properly and slight seizure from corrosion products might have been part of that issue. Or might not................

    Very simple and reliable, as often the clever and effective ideas are.
    JohnW

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    Default More Brake ???

    Quote Originally Posted by JohnW View Post
    Thanks Wildebeeste.

    There is a friction-based adjustment take-up mechanism inside the pistons on these too, and I guess the square seals do the job of pulling the piston back a tad a bit better than round ones, as Renault changed from round to square during the R10 model run. Early cars were at times plagued by groaning noises from the rear brakes (four wheel discs of course) and a mixture of pads not pulling back properly and slight seizure from corrosion products might have been part of that issue. Or might not................

    Very simple and reliable, as often the clever and effective ideas are.
    I've had a leaky rear caliper on my R8 and have just pulled it to look over. I also looked over a couple of other calipers I had sitting around and found every one of them have square seals, besides the one I just pulled. I had the one that's leaking rebuilt about two years ago and it never sealed properly. I've often wondered if the company that did it just measured it and threw in there what they thought would work...

    So in pulling that caliper apart today, a question popped up. One, when pulling the pistons out of my other calipers I have never found any clips holding the piston dust cap in there. Does this belong in my caliper, or is it just something this company put in there that they shouldn't have? Like I said, I've pulled maybe a half dozen Renault calipers apart and never found a clip in any of them.

    I'll include a pic or two of the leaky caliper... just to show what I'm talking about. The metal clip on the right and seal to the right are the ones that were in the leaky piston. The one on the bottom left is my new one, going on there in the morning.

    This brings up another question, is there a source for exploded parts diagrams?
    Attached Thumbnails Attached Thumbnails Brake caliper- round or square seal.-photo-18-.jpg   Brake caliper- round or square seal.-photo-17-.jpg   Brake caliper- round or square seal.-photo-16-.jpg  

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    Quote Originally Posted by Gordinowitz View Post
    I've had a leaky rear caliper on my R8 and have just pulled it to look over. I also looked over a couple of other calipers I had sitting around and found every one of them have square seals, besides the one I just pulled. I had the one that's leaking rebuilt about two years ago and it never sealed properly. I've often wondered if the company that did it just measured it and threw in there what they thought would work...

    So in pulling that caliper apart today, a question popped up. One, when pulling the pistons out of my other calipers I have never found any clips holding the piston dust cap in there. Does this belong in my caliper, or is it just something this company put in there that they shouldn't have? Like I said, I've pulled maybe a half dozen Renault calipers apart and never found a clip in any of them.

    I'll include a pic or two of the leaky caliper... just to show what I'm talking about. The metal clip on the right and seal to the right are the ones that were in the leaky piston. The one on the bottom left is my new one, going on there in the morning.

    This brings up another question, is there a source for exploded parts diagrams?
    I have never seen the clips on the dust caps either but that's not to say they were never there.
    When I ordered new rebuild kits for my calipers I specified square seals but my supplier said to use the round seals as they seal better and last longer. So, better a squeaky caliper than a leaky one.

    Paul Tomlinson
    R1135 Gordini 1968.
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    Alpine GTA- ATMO 1987.
    Jaguar X Type 2002.

  20. #20
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    Quote Originally Posted by Gordinowitz View Post
    I've had a leaky rear caliper on my R8 and have just pulled it to look over. I also looked over a couple of other calipers I had sitting around and found every one of them have square seals, besides the one I just pulled. I had the one that's leaking rebuilt about two years ago and it never sealed properly. I've often wondered if the company that did it just measured it and threw in there what they thought would work...

    So in pulling that caliper apart today, a question popped up. One, when pulling the pistons out of my other calipers I have never found any clips holding the piston dust cap in there. Does this belong in my caliper, or is it just something this company put in there that they shouldn't have? Like I said, I've pulled maybe a half dozen Renault calipers apart and never found a clip in any of them.

    I'll include a pic or two of the leaky caliper... just to show what I'm talking about. The metal clip on the right and seal to the right are the ones that were in the leaky piston. The one on the bottom left is my new one, going on there in the morning.

    This brings up another question, is there a source for exploded parts diagrams?
    Well, I've never seen a clip like the one on your photo, and I've owned my 1964 R1130 for 39 years.

    My experience is that they seal perfectly well, PROVIDED:
    (a) the piston isn't scored more than very fine scratch marks
    (b) the groove that the seal sits in is free of corrosion pits - I polish them with fine wet and dry rubbing paper.

    I've used square seals for about 30 years and have never had a leak. I've replaced them occasionally, mostly to clean out the seal groove. Now I run silicone fluid to avoid hygroscopic absorbtion of water precisely where you don't want it.

    Exploded parts diagram is easy - if you have the factory parts manual. Send me a PM with your email address and I'll scan it for you sometime in the next couple of weeks.

    Cheers
    JohnW

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    Quote Originally Posted by Paul T View Post
    I have never seen the clips on the dust caps either but that's not to say they were never there.
    When I ordered new rebuild kits for my calipers I specified square seals but my supplier said to use the round seals as they seal better and last longer. So, better a squeaky caliper than a leaky one.
    I've never had a problem with square seals and they changed FROM round to square. Maybe the round seals are more compliant in the base of the groove in the calliper if it is corroded a bit?

    Either type is fine IMHO if the groove in the calliper is clean and free of corrosion pits.
    JohnW

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    Quote Originally Posted by Gordinowitz View Post
    This brings up another question, is there a source for exploded parts diagrams?
    Located below is a web address for the PR837 R1135 Gordini parts catalogue, it may help. The rear brake caliper diagram is illustrated on page 43.40.

    http://hppassion.free.fr/Documentati...P.R.%20837.pdf

    There should not be any circlip holding the dust cover in place, and the dust cover that came off doesn't look anywhere near the right size. Also it looks like a round section seal in the caliper, it looks like as you say, they used whatever they had. And then used an under size seal that has leaked.
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    Quote Originally Posted by JohnW View Post
    Hi Phil,

    If you do the master cylinder and callipers, it is only 4 more things to unfasten to put new hoses on it. The only other thing I replaced is that pressure limiting valve.

    This is the perfect opportunity if you are ever going that way. Not that standard fluid isn't perfectly adequate. I found it worth the extra effort, but that's just me.

    Either way, good luck with the callipers - clean extremely well in the grooves behind the sealing rings. You'll likely find white powder and pit corrosion in there, but rubbing with folded fine wet and dry can smooth things enough to get sealing.
    best thing to do with the rear pressure limiting valve is junk it in favour of a simple T piece. It doesn't totally cure the tendency for the fronts to lock in the wet but it helps heaps. Peter

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    I do recall a Renault Service bulletin, from the 1960's era, advising of a change to caliper seal section from round to square. Renault stated, at the time, that the change had been made to improve the RETURN of the piston, after brake application, in order to reduce risk of pads remaining in contact with disc and that this was achieved by the distortion of the square section seal, working like a 'spring' and returning piston to original position, after iChat brake application. Of course, after the pads wear a bit, a heavy application of brake pedal would result in the piston moving slightly THRU the seal, thus taking up the pad wear and maintaining a constant pedal height.

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    Quote Originally Posted by Rod Slater View Post
    I do recall a Renault Service bulletin, from the 1960's era, advising of a change to caliper seal section from round to square. Renault stated, at the time, that the change had been made to improve the RETURN of the piston, after brake application, in order to reduce risk of pads remaining in contact with disc and that this was achieved by the distortion of the square section seal, working like a 'spring' and returning piston to original position, after iChat brake application. Of course, after the pads wear a bit, a heavy application of brake pedal would result in the piston moving slightly THRU the seal, thus taking up the pad wear and maintaining a constant pedal height.
    Thanks Rod. That makes perfect sense. Most kits I have bought in the last 20 years (not many, truth to tell, have been square and I haven't had any rear wheel groaning since I changed to square. Better RETURN, I judged, exactly as you say.

    Cheers
    JohnW

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    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

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