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Drilled or Slotted thats the question?

Tweaky Feb 21, 2003

  1. Tweaky

    Tweaky New Member

    What is the best option to go for on a new set of discs? Drilled, or slotted? I like the look of the drilled discs, but am worried they will crack early. Has anyone got any experience of drilled discs and their life span compared to slotted?

    Any help is much appreciated /ubbthreads/images/graemlins/froggie_red.gif
  2. Crafty

    Crafty Member

    IME Drilled discs tend to crack earlier, from the holes outwards.
    I'd go grooved.
  3. ChrisT

    ChrisT Member

    Holes vs Slots do different things to aid in braking. The holes are to remove excess gas from the disc surface to reduce brake fade, while slots are there to remove the glazed layer on top of the pads makign better contact between pads and discs.

    You're right that some discs which are drilled are supposed to be weaker. This isn't always the case, discs which have been drilled out after being cast are weaker, but discs which have had the holes cast in them are much stronger.


  4. Gambba

    Gambba Active Member

    Is not the more important question here, 'What is the difference between drilled, sloted and grooved' ?

    I don't think cracking is really an issue for most discs, I would of thought that cracking only ever occurs due to overheating and that's why these other options are available, which allow greater heat dissapation.

    I don't know real details, as I've never been involved in racing or fast street brakes before.
  5. Tweaky

    Tweaky New Member

    I love the look of the Drilled discs, but i don't want to shell out £300+ on two drilled discs and have them crack within the first 10/15k miles. I am pretty sure the discs i am looking at are drilled, not cast. They are from Hispec Motorsport.
  6. Andiroo

    Andiroo New Member

    Hey guys, the answer is drilled discs with good quality pads, anything else is a compromise.

    Grooves or slot disc should only be offered on pre-cast discs as they are not physically suited to being drilled because of heat stress /ubbthreads/images/graemlins/blush.gif although I have to say they are still offered on the market /ubbthreads/images/graemlins/frown.gif Quality drilled discs are cast, not drilled after /ubbthreads/images/graemlins/tongue.gif

    You are partly right Chris, although drilled discs also take glazing from the pad surface.

    The main benefit of drilled discs (apart from partial deglazing) is getting rid of the heat from the pad/disc surface - this is where it is far superior to the other offerings, taking the heat into and out of the disc rotors.

    As for cracks in the drilled parts of a proper cast drilled disc - it's all down to maintenance. I have 380mm drilled discs with 20k miles, including 11 trackdays on Sport Yellow Pagids, and they are slighlty worn but still mint.

    Every 2k miles I just take of the wheel, take out the pads and floating disc and clean all the holes and rotor. With the pad just take a Dremel or hard sandpaper and take of the glaze and shampfer the edges.

    If you do trackdays on drilled discs, do expect DIY maintenance (or heavy servicing bills). If you dont spend this time on maintenance, dont buy Porsche/Movit/Brembo brakes with performance pads - unless you want them to crack after 6-12k miles, choice is yours guys /ubbthreads/images/graemlins/wink.gif

    BTW with a performance caliper/disc/pad I use Castrol SRF 4.1 as a minimum, coz that reduces heat thru the pad as well.


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