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Thread: Drilling stock rotors

  1. #11
    Join Date
    Aug 2010
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    Melbourne, Vic
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    434
    Users Country Flag

    The metal becomes more brittle after heat treatment, likely they will crack

    Your best bet is change your brake fluid or upgrade the disks / pads I recon.

  2. #12
    Join Date
    May 2008
    Location
    Adelaide, SA
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    739
    Upgrade fliud, pads, add cooling.

    The Group N Historics have to manage without drilled nor slotted rotors, and damn some of those cars are fast!
    Cheap, Fast, Reliable. Choose two.

  3. #13
    Join Date
    Oct 2010
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    Melbourne, VIC
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    Users Country Flag Thread Starter
    OK, I'll get the fluid changed, install my QFM A1RM pads and hope the new wheels give more airflow to the rotors.
    It's just that I brake so softly on the road that the pads will go green and I will need to re-bed them before each track outing.

    Thanks to all.

    BTW Grey cast iron (which all rotors are made of unless your have CF or ceramic) doesn't heat treat at the temps brake rotors get to so the warning against drilling used rotors is probably to do with the possibility of micro-expansion cracks forming during use and these being across the drill holes (which would mean that they would grow VERY quickly with more thermal cycling).
    Last edited by kaanage; 15-02-2012 at 10:28 AM.
    Resident grumpy old fart
    VW - Metallic Paint, Radial Tyres, Laminated Windscreen, Electric Windows, VW Alloy Wheels, Variable Geometry Exhaust Driven Supercharger, Direct Unit Fuel Injection, Adiabatic Ignition, MacPherson Struts front, Torsion Beam rear, Coil Springs, Hydraulic Dampers, Front Anti-Roll Bar, Disc Brakes, Bosch ECU, ABS

  4. #14
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    May 2008
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    Erskineville, NSW
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    Quote Originally Posted by kaanage View Post
    Good point - stock and 2 years (3 actually, though 1 wa spent sitting in VW storage). It will be changed before the next track outing (when my rear LCA bushes gat replaced)
    That's where I'd start as it's what the problem is. Drilled rotors & cooling are peripheral.

    Try Motul RBF600 or Ferodo Racing 5.1. Change every 12 months (or sooner) if doing track days.
    carandimage The place where Off-Topic is On-Topic
    I used to think I was anal-retentive until I started getting involved in car forums

  5. #15
    Join Date
    Jan 2009
    Location
    Brisbane
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    2,297

    Bear in mind the differences between a DOT5 and Dot 5.1. You should not mix different ratings and certainly not compounds (silicone and glycol based fluids) Brake fluid - Wikipedia, the free encyclopedia and/or D.O.T. 5 Brake Fluid

    I hadn't realised such a difference between DOT4 and Dot5 boiling temps. food for thought.

    I've always ran a dot4 and haven't had any issues in VW, my subaru would boil occasionally on track days.
    Track Car: 06 Polo GTI Red Devil mkII
    Daily: 2010 VW Jetta Highline
    Gone but not forgotten: 08 Polo GTI
    ** All information I provide is probably incorrect until validated by someone else **

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