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  1. #21
    Join Date
    Aug 2013
    Location
    Canberra
    Posts
    100
    When the rotors were installed, were they indexed properly?
    There is normally some runout in both the rotor and the hub. You should mount the rotor
    to the hub in each of the 5 possible orientations and measure the combined run out in each
    then leave it mounted in the orientation that had the least runout.

    If you don't then the high spots on each face wear faster resulting in the disk being thinner
    at those points. As a result as the wheel rotates under braking the pads see varying thickness
    of the rotor, and the pedal pulses, possibly the shudder you are feeling.

    Dave !
    Luck is the residue of design

  2. #22
    Join Date
    Nov 2016
    Posts
    532
    Who would do that?

    Never had to do that ever

    There must be more at play

  3. #23
    Join Date
    Aug 2013
    Location
    Canberra
    Posts
    100

    Disk Thickness Variation

    Quote Originally Posted by craze View Post
    Who would do that?
    I did that! on my previous VT and my current GenF

    From a 1999 Holden Techline:

    1c. Cause of Brake Shudder
    Brake shudder primarily occurs as a result of
    variation in the thickness of the brake disc. This
    in turn causes variations in brake surface
    pressure as the varying thickness disc passes
    between the pads during braking.
    The variation in thickness of the disc can be
    measured with a micrometer as shown in Fig 1.
    NOTE. A disc that varies in thickness by more
    than .015mm (15 micron) will cause brake
    shudder.

    New discs develop Disc Thickness Variation
    (DTV) as a result of excessive lateral runout in the
    disc combined with caliper drag during non-
    braking running time. On each revolution of the
    disc a portion of the disc comes into contact with
    the pad. Eventually the disc wears at the point of
    contact thus creating thickness variation.
    Here is more of the techline:
    http://www.dd.id.au/LS1/Brakes/DTV.pdf

    Video showing measuring stacked runout on my GenF GTS.

    Runouts measured were 0.07, 0.08, 0.015 and 0.03mm.
    I put the rotor back to the position that resulted in 0.015mm of runout.

    Seeing that, I don't understand why you would not take the extra 10 minutes.
    Last edited by myBerlina; 01-07-2018 at 09:53 PM.
    Luck is the residue of design

  4. #24
    Join Date
    Nov 2016
    Posts
    532
    So if it doesnt produce shudder when new its non issue?

    Further to that not a single shop would do that even the "brake experts"

  5. #25
    Join Date
    Aug 2013
    Location
    Canberra
    Posts
    100
    Quote Originally Posted by craze View Post
    So if it doesnt produce shudder when new its non issue?
    Well there is a one in 5 chance it goes on in the perfect orientation, chances are the orientations one each
    way are close enough to be in spec still, so you may not develop enough DTV to result in shudder.

    I have always done it because I saw the obvious sense in it, and never had shudder.
    From memory there was a bigger difference when I did it on my VT (with just a 330mm rotor).

    Obviously a bigger runout will wear those spots faster leading to DTV and then shudder sooner, a smaller runout
    will take longer to develop enough DTV to create shudder. Presumably if the runout is less than .05mm Holden
    thinks it will take longer to wear out the rotor than develop enough DTV to result in shudder.


    Quote Originally Posted by craze View Post
    Further to that not a single shop would do that even the "brake experts"
    Maybe that is why

    Quote Originally Posted by craze View Post
    I went through this years ago and multiple shops cannot diagnose it
    until

    Quote Originally Posted by craze View Post
    Aps frankston got mine sorted never had an issue after that
    did index of the rotors as a matter of course, or just lucked into the correct orientation. Maybe you had
    bad hubs with excessive runout and when indexing them found that and replaced the hubs?

    Maybe APS had read the Holden Techline or just follow good procedures, try googling 'Indexing brake rotors'
    there are plenty of hits, it is not a radical or rare thing.

    The fact that Holden felt the need to issue the Techline does suggest that at least some places were just slapping
    the rotors on, and some didn't even bother to clean the hub first, leading to upset customers, with the symptom
    you and the original poster seem to have suffered from.
    But I would be disappointed if none did it right.
    Luck is the residue of design

  6. #26
    which makes it a 1 in 10 chance that a set of front rotors goes on without shudder at all. I guess that's why 9/10 Commodores, cars in general, are replacing their rotors every few months. Unless they aren't.
    Ben
    1978 Firebird Formula 6.6L W50
    2002 HSV Clubsport R8 255

  7. #27
    Join Date
    Sep 2010
    Location
    Bondi
    Posts
    1,060
    I must be one of those 1 in 10 because none of my cars have ever suffered from brake shudder.
    Squeal yes but a few hard stops usually cleans that up no matter what pads I've used.
    I had HQ brakes on the front of my UC Torana with A9X rear end discs.
    My VS Super6 had VT HSV brakes on front and VN GrpA brakes on rear.
    And my Senator has AP 6/4, 362/350 discs. Originally AP discs now DBS T5000 Front and T4000 on rear.
    I remember when the VT first came out there was a lot of people getting brake shudder from having the front wheel nuts torqued up to tight.

  8. #28
    Early days, but a month on the new DBA SP range of brake pads seem to be ok. Only because within the first few weeks there was often already signs of shudder returning with other brands.
    Ben
    1978 Firebird Formula 6.6L W50
    2002 HSV Clubsport R8 255







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