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Author Topic: cross drilled discs  (Read 1553 times)

Offline jammac

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cross drilled discs
« on: 29 October 2007, 14:31 »
hi

Ive just bought new front discs for my mk2 gti 8v 1991. a guy from work said to just buy the standard discs and cross drill them myself. My old discs are already cross drilled so i was just gonna take one off and back drill the new disc.

anyone else ever done this and would i actually benefit having cross drilled holes over my standard vented disc?? or is it just gash!

they are the bog standard 239mm discs so my braking needs all the help it can get!!!!!!

cheers
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Offline Horney

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Re: cross drilled discs
« Reply #1 on: 29 October 2007, 14:43 »
Cross drilling actually reduces the contact surface so makes your brakes worse on first bite. Their purpose was to stop gas build up between the pad and the disc under high heat conditions. This doesn't really happen with modern pad materials and so is somewhat pointless. Drilled discs also have a reputation of cracking as the holes weaken the disc, this is why they rarely used in motorsport these days. I've never had any crack BUT I used to run drilled discs on my minis and found they warped really quickly especially when hot and then slammed into a cold puddle.

What you want are grooved dics. As with drilled you lose a certain amount of braking area BUT these help keep your pads in top condition by constantly skimming them and therefore reducing any build of glazing etc. The downside is they eat pads.

Nick
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Offline Uruk Hai

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Re: cross drilled discs
« Reply #2 on: 29 October 2007, 16:10 »
^^^ As above realy, I put a pair of zimmerman cross drilled front discs and pagid fast road pads on my first Golf and I never realy noticed much difference under normal breaking but when breaking hard and often from high speed they realy came into thier own and didnt fade at all.
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Offline Horney

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Re: cross drilled discs
« Reply #3 on: 29 October 2007, 16:18 »
It's all about good pads really. OE discs are easily up to the job.

Nick
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Offline Conker

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Re: cross drilled discs
« Reply #4 on: 29 October 2007, 22:05 »
My 16v'er has got grooved brembo discs and although breaking is very good, you get quite a bit of noise and vibration under heavy breaking.

I think i would go for OE discs next time, with good pads (as Horney said).
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VeeDubGTI16v

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Re: cross drilled discs
« Reply #5 on: 30 October 2007, 10:29 »
definately dont drill them yourself! cross drilled discs have to be cast cross drilled otherwise the holes are weak as said.
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Offline jammac

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Re: cross drilled discs
« Reply #6 on: 30 October 2007, 14:57 »
cast crossed drilled? they wouldnt be drilled then
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VeeDubGTI16v

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Re: cross drilled discs
« Reply #7 on: 31 October 2007, 10:20 »
cast with holes in! you know what i mean  :laugh:
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Offline jammac

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Re: cross drilled discs
« Reply #8 on: 31 October 2007, 13:19 »
yeah sorry im being pedantic.......on nightshifts this week so i hate the world  :evil:
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