Correct shimming of brake calipers??? | FerrariChat
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Correct shimming of brake calipers???

Discussion in '348/355' started by ///Mike, May 16, 2017.

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  1. ///Mike

    ///Mike F1 Veteran

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    #1 ///Mike, May 16, 2017
    I know I've seen diagrams in a factory Ferrari manual illustrating measuring and shimming the brake caliper position but I'm not finding it in either the 348 or 355 workshop manuals. I noticed recently (via measurement) that my calipers are not exactly centered on the discs as I'd expect them to be, but before I set about to center them I'd like to know where they're *supposed* to be according to Maranello. Can anyone point me to the factory procedure for locating the calipers on the 348/355?
     
  2. Wade

    Wade Three Time F1 World Champ
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    #2 Wade, May 16, 2017
    Section G of the 348 WSM is for the wheels and brakes, but nothing there for service/maintenance on the calipers themselves.
     
  3. Dave rocks

    Dave rocks F1 World Champ
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    #3 Dave rocks, May 16, 2017
    Last edited by a moderator: Sep 7, 2017
  4. Wade

    Wade Three Time F1 World Champ
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    #4 Wade, May 16, 2017
    Yeah, nothing like that in the 348 WSM. Not in mine anyway. The only info and procedures regarding calipers are for changing the brake pads and bleeding the system.

    Good info, thanks.
     
  5. ///Mike

    ///Mike F1 Veteran

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    #5 ///Mike, May 16, 2017
    Thank you, Dave. I knew I'd seen it but couldn't remember where. Sooo frustrating to draw a blank like that. I checked the 355 manual but gave up when the discussion shifted from pad changing to bleeding. Turns out bleeding is between pad changing and caliper shimming (crazy Italians ;) ).

    I was 99.46% certain the caliper should be centered but preferred to confirm the proper factory procedure before ordering parts. Thanks again!
     
  6. Badabing!

    Badabing! Formula Junior

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    #6 Badabing!, May 16, 2017
    You use the thickness gauge to measure the distance between the rotor face and what surface on the caliper? New pads with pistons retracted? New pads with pistons extended? What ?
     
  7. Dave rocks

    Dave rocks F1 World Champ
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    #7 Dave rocks, May 16, 2017
    My pleasure, Mike. I go thru the same crap with the manuals as it seems stuff is scattered :)

    Rotor surface to pad surface with pistons retracted is what I did. The 355 calipers don't float like some systems (that have pistons on a single side). The point is to get them setup close to symmetric from the start so they wear even. But, the pistons on each side of the caliper will really allow them to evenly wear. If I say that in a way that makes sense ;)
     
  8. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #8 Rifledriver, May 16, 2017
    Don't recall on 355 but many of the cars have different size pistons top and bottom to purposely alter the pressure on leading and trailing ends of the pad. Pads often wear a little unevenly because of it and is normal. They design in less pressure on the leading end to reduce brake squeal. For that to all work correctly the caliper needs to be more or less straight. It also should be more or less centered so the pistons are not over extended when the pads wear out.
     
  9. taz355

    taz355 F1 Veteran
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    #9 taz355, May 16, 2017
    So I assume they come centered so how do they get out of center??
     
  10. ///Mike

    ///Mike F1 Veteran

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    #10 ///Mike, May 16, 2017
    Considering we're talking about Ferrari I'm not sure that's a safe assumption. ;)

    In truth, it's really easy to lose shims when removing the calipers and replacing the calipers.
     
  11. taz355

    taz355 F1 Veteran
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    #11 taz355, May 16, 2017
    So is it a fair assumtion to make that if the pads are wearing evenly the calipers are centered??
     
  12. Dave rocks

    Dave rocks F1 World Champ
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    #12 Dave rocks, May 16, 2017
    Exactly. Most don't know the shims are there until they hear them hit the floor :)

    Yep.
     
  13. ///Mike

    ///Mike F1 Veteran

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    #13 ///Mike, May 16, 2017
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    The pistons are indeed staggered and the purpose for that is to reduce pad taper. Without piston stagger the leading edge of the pad wears a good bit faster than the trailing edge. The pic below is of pad taper on a track car with four piston calipers where all the pistons are the same size. This taper would be much less noticable in street use.

    Staggering the piston sizes doesn't totally eliminate pad taper unless the brakes are used in the exact manner expected by the engineers. The 355 (and I assume the 348) has 38/40 piston diameters. If memory serves, most modern Porsches have a 4 mm stagger (36/40 IIRC). Maybe the Brembo engineers figured Porsche drivers would use their brakes harder.
    Image Unavailable, Please Login
     
  14. ///Mike

    ///Mike F1 Veteran

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    #14 ///Mike, May 16, 2017
    Not really. The same clamping force is being exerted by both sets of pistons, regardless of the caliper position (assuming that all four pistons/bores are in good shape). I think it's really more to ensure clearance for new pads. But it really shouldn't matter to clamping force or pad wear.
     
  15. taz355

    taz355 F1 Veteran
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    #15 taz355, May 16, 2017
    The Brembi engineers were right to design the porsche calipers that way.

    Likely because they need to catch up to the Ferrari. Ha ha
     
  16. Badabing!

    Badabing! Formula Junior

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    #16 Badabing!, May 16, 2017
    That was me.
     
  17. Dave rocks

    Dave rocks F1 World Champ
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    #17 Dave rocks, May 16, 2017
    Well, that's true. One sides Pistons will just stroke a bit more until the pad makes contact.

    I don't see pad changes without removing the caliper to be very practical. One, trying to move the Pistons in is not easy on the car (especially without damaging the paint) and if the rotor has a worn lip, won't be easy to get the pads out. Perhaps the pros have some tricks. I seem to recall measuring my new pad thickness and finding them very consistent.

    The Ferrari spec of .3mm seems a bit overstated but IIRC, I had not trouble meeting it.
     
  18. ///Mike

    ///Mike F1 Veteran

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    #18 ///Mike, May 16, 2017
    And me. Owned a multi-marque import repair shop for years. Track prepped cars for a couple of decades. *Shoulda* known it by rote but only remembered they were there right after the "Where the hell did that extra washer come from?" hit the floor. Managed to find them all but I wonder if everyone who'd been there before me was as lucky. Regardless of how it happened the calipers are a bit off center, so not sure if new pads could be fitted to both sides. But really glad to know that I'm not the only who forgets things. :)
     
  19. m.stojanovic

    m.stojanovic F1 Rookie
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    #19 m.stojanovic, May 16, 2017
    I haven't had problem with the "lip" on the outer edge of worn rotors when removing (or installing new) pads. The height of the lip should be where the original thisckness of the rotor was over which the pads went in or out easy so the pads should also pass the lip without getting stuck (unless the "lip" is actually higher than the original rotor thickness due to the rotor material being also pushed up at the outer edge?).
     
  20. ///Mike

    ///Mike F1 Veteran

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    #20 ///Mike, May 16, 2017
    Dave, I can't remember the last time I removed a caliper to swap pads unless that was the only way to change them (and I've changed a ton of brake pads). That's one of the many beauties of this style of caliper-- you can change pads much quicker than with floating calipers. Also, it's a giant PITA to refit the calipers when they're loaded because of the spacers. Far easier to coax the spacers into place when you can move the caliper well away from the mounting tabs and that's only possible without at least the outboard pad out of the way.

    But even if you do remove the caliper it still needs to be centered on the disc to some degree on reinstallation or you won't be able to mount the caliper properly. Now that I think about it I'm envisioning a nightmare scenario where the caliper is removed to swap pads and not enough spacers are fitted on reinstallation. The consequences would be ugly, whether it led to the caliper not being properly affixed or the mounting ears breaking off. All the more reason to leave the caliper in place and swap pads in the prescribed manner (pages G12 and G13 in the 355 manual).
     
  21. Dave rocks

    Dave rocks F1 World Champ
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    #21 Dave rocks, May 17, 2017
    Mike - how did you push the pistons in while calipers were installed?

    In my situation I was installing new rotors so perhaps I just did not bother with the effort but I saw no good way. Perhaps some sort of wedge.....
     
  22. Dave rocks

    Dave rocks F1 World Champ
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    #22 Dave rocks, May 17, 2017
    That is true but the pad gets trapped by the lip and the pistons pushing the pad. Again, it's about how to push the pistons back without damaging the caliper paint. I'm sure there is a way but I was changing the rotors anyways.
     
  23. johnk...

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    #23 johnk..., May 17, 2017
    I usually don't removed calipers to replace pads either. I just pry between old pad and disk on the inside pad to retract the pistons. Then remove old pad, insert new one. Then repeat for the outside pad. Then there are calipers like on a BMW that flip back to expose the pads. Only time I remove calipers is if the disks are to be replaced or resurfaced, which you are really supposed to do at every pad change (street car).
     
  24. Dave rocks

    Dave rocks F1 World Champ
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    #24 Dave rocks, May 17, 2017
    I've only done about 5 brake jobs my entire life as I change cars often (DD's)

    So, given I was replacing the rotors I likey did not bother trying hard enough to find a trick to push in the pistons without hurting the paint. That's all I'm really saying. One thing I know is your not getting a c-clamp in there :)
     
  25. ahirsh

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    #25 ahirsh, May 17, 2017
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