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Rebuild rear brake calipers

Discussion in '365 GT4 2+2/400/412' started by Arvid, Jun 3, 2014.

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  1. Arvid

    Arvid Formula Junior

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    #26 Arvid, Feb 15, 2016
    Yes,better double check it Rick. I have looked through the catalogues with the provided measures but not one of them matches all 3 dimensions.
     
  2. Piston.Broke

    Piston.Broke Karting

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    #27 Piston.Broke, Feb 21, 2016
    Last edited: Feb 21, 2016
    Hi Arvid.

    The mystery deepens...

    I have measured the front brake caliper pistons and the details are as follows:

    42 mm in diameter
    overall height 29.5 mm
    internal bore 22.3 mm

    The calipers (ATE) look like they have been fitted to the car from new. It would appear that a number of BMW ATE calipers from the mid to late 70's also used 4 spot 42 mm calipers. They obviously bolt straight on the same pattern as the normal 40 mm caliper. Externally, they look identical.

    I believe that they may be the same as a 42 mm (4 spot) caliper (ATE) from the following BMW models:

    BMW

    Model Type Year
    2500 00.69-00.77
    2800 00.69-00.77
    2.8 00.75-00.77
    3.0 00.71-00.77
    3.3 00.74-00.77

    All the above models came with standard ATE twin 42 mm piston calipers and the caliper pistons size also seem to match.

    Cheers!

    Piston.Broke
     
    Sergio Tavares likes this.
  3. Arvid

    Arvid Formula Junior

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    #28 Arvid, Feb 21, 2016
    The plot thickens :)

    Rick, this just doesn't add up. I've skimmed through different catalogues and BMW only had 2-pot calipers in 42mm. All their 4-pot of that era where 40mm and the above mentioned BMW-models all came with 4-pot 40mm or 2-pot 42mm.

    In any case the pistons and parts might be the same and parts for the 2-pot 42mm could fit Your 4-pot 42mm.

    Have you sourced the parts needed ?
     
  4. Piston.Broke

    Piston.Broke Karting

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    #29 Piston.Broke, Feb 21, 2016
    Thanks Arvid.
    OOPS!
    Spot the obvious error!
    I was referring to the rear (2 spot) 42mm caliper kits for the BMW models mentioned.
    I was hoping to have the calipers professionally rebuilt but unfortunately I cant find any brake specialist (in Australia) who is interested in doing the work. What vehicle used the 4 spot calipers (ATE) with the piston size as described?

    Any ideas?

    Cheers !

    Rick.
     
  5. Arvid

    Arvid Formula Junior

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    #30 Arvid, Feb 22, 2016
    Rick,

    I'm having trouble following you... :) Are Your front calipers 2-pot or 4-pot ? There is no 42mm 4-pot ATE calipers from that era,only 2-pot. Do You want the details for the 40mm 4-pot ?

    Arvid
     
  6. Piston.Broke

    Piston.Broke Karting

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    #31 Piston.Broke, Feb 22, 2016
    Hi Arvid,

    The front calipers are 42mm - 4 piston calipers and they look externally identical to the 'normal' Ferrari 400 - 40mm - 4 piston calipers I have seen.

    I will take your word for it that there were no 42mm - 4 piston calipers made by ATE in the mid to late 70s.

    I will continue my research and if I can find a source for the 42mm - 4 piston calipers, I will let you know. (As everyone else's 365/400/400i/412s appear to have 'standard' 40mm - 4 piston calipers, it is probably somewhat 'academic' to them and I don't think there will be much interest in the outcome.

    Thanks for your help anyway.

    Regards,

    Piston.Broke
     

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  7. Arvid

    Arvid Formula Junior

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    #32 Arvid, Feb 22, 2016
    Last edited by a moderator: Sep 7, 2017
    No,don't take my word for it because I can't say without a doubt there where no ATE 4-pot 42mm. They just don't show up in the catalogues. Your car is the exception that breaks the rule :)

    If I where You I would contact ATE Classics and ask for advice. The Germans most certainly know what they are doing. It wouldn't surprise me if they are the same parts as 2-pot 42mm.

    If You look at the attached picture,do they resemble ? The surface against the pads have an unusual uneven surface. These are the ATE pistons that match the measurments.

    Arvid
    Image Unavailable, Please Login
     
  8. Piston.Broke

    Piston.Broke Karting

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    #33 Piston.Broke, Feb 24, 2016
    Thanks again Arvid.
    Yes, I have already had a look at kit you have in the photos. The pistons size match as you say but my pistons don't have the cut away section.
    Good advice to contact ATE direct.
    I will let you know what I find out.
    Regards,
    Piston.Broke.
     
  9. geffen365gtc/4

    geffen365gtc/4 Karting

    Mar 12, 2005
    191
    #34 geffen365gtc/4, Feb 24, 2016
    I needed some new pistons when doing a brake rebuild on my C4. I just popped one out and took it to a local machine shop. Two days and $40 later I had several in my hand.

    Geffen
     
  10. Piston.Broke

    Piston.Broke Karting

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    #35 Piston.Broke, Feb 25, 2016
    Thanks Geffen,

    That may be my back up plan.

    Cheers!

    Piston.Broke
     
  11. NavFerrari

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    #36 NavFerrari, Jun 18, 2021
    Wow Arvid,

    Cheers mate .This is really cool .Thanks a million mate.


    Sent from my iPhone using FerrariChat.com mobile app
     
  12. Andres_1979

    Andres_1979 Rookie

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    #37 Andres_1979, Jul 19, 2022
    Hi guys I have the same problem with my pistons, they are 42mm!!! Where did you get the service kit for them? Which brand/model did you buy?
    Regards
    Andres
    PS: My car is a 1979 400GT
     
  13. Andres_1979

    Andres_1979 Rookie

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    #38 Andres_1979, Jul 19, 2022
    Hi Arvid, seems like you are the expert!!! My car also has 42mm pistons, do you know which product will fit to it to restore my brakes?
    Regards
    Andres
     
  14. Arvid

    Arvid Formula Junior

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    #39 Arvid, Jul 19, 2022
    Hi Andres,

    I did research the ATE calipers some years ago and I really didn't find anything useful on the 42mm pistons. Rick (Piston.Broke) reasearched it further I think as his car has has same brakes as yours. Send him a PM or maybe contact ATE : ATE - Brakethrough Technology (ate-brakes.com). Frenkit also has a good catalogue for searching : Brake part distributor - Frenkit

    The best would be to remove one piston and measure it. I could probably help you find correct parts then.
     
  15. Andres_1979

    Andres_1979 Rookie

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    #40 Andres_1979, Jul 19, 2022
    Hi Arvin, thx a lot for your message and help

    Which measures do you need? The piston measures, the caliper internal measure? Or the actual rubber (I have the original)

    I will try to reach Rick and see what did he do

    Regards

    Andres

    I w
     
  16. Arvid

    Arvid Formula Junior

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    #41 Arvid, Jul 19, 2022
    Measure the piston height and post a picture of how it actually looks. That would help.
     
  17. Andres_1979

    Andres_1979 Rookie

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    #42 Andres_1979, Jul 19, 2022
  18. Andres_1979

    Andres_1979 Rookie

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    #43 Andres_1979, Jul 19, 2022
  19. Andres_1979

    Andres_1979 Rookie

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    #44 Andres_1979, Jul 19, 2022
  20. Arvid

    Arvid Formula Junior

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    #45 Arvid, Jul 20, 2022
    The 34mm are the same as listed earlier in the thread. The 42mm however is an illusive part. I find 42mm used on BMW and Porsche but they are not 100% the same. The top of piston,where brake pad sits,has a cutaway for brake pad shims. Don't know if it will influense the pressure on brake pad on your application but likely not. Either way part nr. is Budweg 234201 or Frenkit P422901. Measures are 42x29,5. Complete seal kit would be Frenkit 242004 - BMW 34211103482 - Audi 411698471 - Porsche 91135290500.

    But there's a but here. These seals would possibly only fit the mentioned pitons as the inside diameter of the seal corresponds to these pistons top and not necessary your 42mm pistons.

    Wait for Rick to answer and maybe send an email to ATE Classic.

    Image Unavailable, Please Login
     
  21. Arvid

    Arvid Formula Junior

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    #46 Arvid, Jul 20, 2022
    There are alternatives. For instance from Brembo. They are 0.5mm higher which I'm sure would be fine. If you compare these measures with your piston maybe they are the same ? If so you could use these pistons and source the original ATE seal kit.
    Image Unavailable, Please Login
     
  22. Andres_1979

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    #47 Andres_1979, Jul 20, 2022
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  23. Arvid

    Arvid Formula Junior

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    #48 Arvid, Jul 21, 2022
    Andres, This would be the seal kit for the pistons mentioned in post 45. I haven't found any exact measurements for those so it's difficult to say if the seal kit would fit or not. Your 42mm ATE's are very illusive. Going through catalogues there are no matching 4-piston 42mm calipers found on any other contemporary cars. Weird. The closest are the 42mm single and twin piston variants used on BMW,Mercedes and Porsche. Parts catalogue for Ferrari 400i and 412 show no alternative other than the usual 40mm.

    I will check some more and let's hope you also get some info from ATE.
     
    Sergio Tavares likes this.
  24. Al Campbell

    Al Campbell Formula Junior
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    #49 Al Campbell, Apr 28, 2023
    I'm currently rebuilding 3 sets of calipers (12 calipers) off two 1980 400i's and an 82 400i, all have 42mm pistons on the front. I managed to purchase 6 replacement 42mm pistons to replace the corroded ones.

    Does anyone know of a current supplier for the 34mm pistons as I need 4 more?

    I also found it unusual that the front caliper mounting bolts on all 3 cars are 1/2-20 UNF and all the rear caliper mounting bolts are M12 x 1.25 bolts. These are very similar pitch thread but 0.7mm difference in outside diameter.

    Cheers,
    Al
     
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