R8/10 Disc Thickness?
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Thread: R8/10 Disc Thickness?

  1. #1
    Fellow Frogger! R8 Dream's Avatar
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    Default R8/10 Disc Thickness?

    I have never been able to figure this out. The R8/10 (R1132) manual says a disc thickness should be 6.5mm +0.15 / -0.0 Does this mean the minimum thickness can only be 6.5mm? So how thick is it when brand new, 6.65mm? If someone has a new disc, can they measure it and tell me what it actually is brand new? Angelo

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    1000+ Posts geckoeng's Avatar
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    Angelo,
    There is no min disc thickness mentioned. New std R8/10 are 6.3 - 6.5. I have 40+ year old discs that are 6mm+ thick still, I have one sample that was being used at 3mm.

    I would say 5.5mm would be a safe measurement to discard a disc.

    R8 Gordini R1135 were supplied with 8.0mm discs, and there are a few suppliers who only supply these today. de.Franzose supply the 6.3, but Meca Parts, I believe supply the 8.0mm. There is a problem with the reproduction discs, They are made from the modern cast iron and wear much quicker than the old discs, and wear uneven.

    The customer R10 I am putting back on the road, at present has brand new, unused discs on the front (10 years old). the car has been standing for that time, discs needed a light sanding to make good.

    Ray
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    Ray geckoeng

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    Quote Originally Posted by geckoeng View Post
    Angelo,
    There is no min disc thickness mentioned. New std R8/10 are 6.3 - 6.5. I have 40+ year old discs that are 6mm+ thick still, I have one sample that was being used at 3mm.

    I would say 5.5mm would be a safe measurement to discard a disc.

    R8 Gordini R1135 were supplied with 8.0mm discs, and there are a few suppliers who only supply these today. de.Franzose supply the 6.3, but Meca Parts, I believe supply the 8.0mm. There is a problem with the reproduction discs, They are made from the modern cast iron and wear much quicker than the old discs, and wear uneven.

    The customer R10 I am putting back on the road, at present has brand new, unused discs on the front (10 years old). the car has been standing for that time, discs needed a light sanding to make good.

    Ray
    Thanks Ray,

    And that's my concern, there is no min thickness.

    I have some 2nd hand discs that are between 6.00-6.5mm.

    If I lightly get them machined what is the point that they will no longer pass a RWC?

    So what do I tell a mechanic if there is no minimum (say 5.5mm?)

    I just don't want to go down this path just to have someone knock them back once its all fitted.

    I do know that the Gordini discs are thicker at 8mm.

    3mm!! Wow, I have one at 5.5mm and I was worried!

    Angelo

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    Too many posts! JohnW's Avatar
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    The word always was that there wasn't enough meat to machine R8/10 discs, as I recall it. I've a feeling the manual has words like "It is forbidden...…".

    I replaced my front rotors at about 45 years and 300,000 km, somewhat under 6 mm, again if I recall correctly. The rears were almost as new (pressure limiting valve....). The replacement rotors are not quite as true as the old, genuine ones!

    Tomorrow I'll have a good look - I'm sure I've seen a minimum thickness quoted somewhere.
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    JohnW

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    I was looking up some info in my old Renault books and ran across the brake section and found what Ray had mentioned as a safe measurement at 5.5mm , new for a R10 is at 6.5mm and the gord units at 8mm. at new .

    Manic GT


    Quote Originally Posted by geckoeng View Post
    Angelo,
    There is no min disc thickness mentioned. New std R8/10 are 6.3 - 6.5. I have 40+ year old discs that are 6mm+ thick still, I have one sample that was being used at 3mm.

    I would say 5.5mm would be a safe measurement to discard a disc.

    R8 Gordini R1135 were supplied with 8.0mm discs, and there are a few suppliers who only supply these today. de.Franzose supply the 6.3, but Meca Parts, I believe supply the 8.0mm. There is a problem with the reproduction discs, They are made from the modern cast iron and wear much quicker than the old discs, and wear uneven.

    The customer R10 I am putting back on the road, at present has brand new, unused discs on the front (10 years old). the car has been standing for that time, discs needed a light sanding to make good.

    Ray
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    Too many posts! JohnW's Avatar
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    I knew I'd seen it somewhere....

    The early MR 68 factory manual (E.A. for Edition Anglais) says everything BUT minimum disc thickness.

    However, the newer 3rd edition of MR 68, which covers R1130, R1132 and R1136 models, specifies 5.5 mm minimum thickness. I was below this significantly when I replaced mine!

    This number is also to be found in the 1973 Haynes manual, in pink, which was my only reference for many years.

    Somewhere in this forum, Simon commented some years ago that the slightly thicker R8 G rotors could be used and it was possible to get the callipers over the discs with new pads. Just..... I imagine it is a bit of a struggle.

    Cheers
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    JohnW

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    I purchased new discs from Mecaparts and needed to get them machined down to 6.5mm to have any chance of fitting them. Don't know if the Gordini's had slightly thinner pads but with the discs as supplied at 8.0mm ,they would bind solid.

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    I remember looking it up last year when doing some work on an r8. Remember finding it as 5.5.. the car I was working on had them failed on a roadworthy at around 5.8. I changed them for some used ones that measured up to 6mm as it was easier than arguing the point with the roadworthy inspector.

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    The discs on my mountain bike are 3mm thick...


    2003 PEUGEOT 206 GTi

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    Quote Originally Posted by chris hartwell View Post
    I purchased new discs from Mecaparts and needed to get them machined down to 6.5mm to have any chance of fitting them. Don't know if the Gordini's had slightly thinner pads but with the discs as supplied at 8.0mm ,they would bind solid.
    Thanks Chris. I guess that answers that one! My new rotors are not quite as true as the originals either. With new pad materials, I'm guessing they won't last as well either.

    Cheers
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

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    I remember years ago that with the R8G brakes if they did not fit we use to sand them down a bit because it was explained that the 8mm rotors where thicker because of the power booster apply more pressure causing additional heat causing them to possible warp .

    So final thought at the dealership was easier to sand pads than to replace rotors ??!! go figure ??

    Manic GT

    Quote Originally Posted by chris hartwell View Post
    I purchased new discs from Mecaparts and needed to get them machined down to 6.5mm to have any chance of fitting them. Don't know if the Gordini's had slightly thinner pads but with the discs as supplied at 8.0mm ,they would bind solid.

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