Drilling or grooving will improve initial performance. When you apply the brakes hard, the pad material vapourizes, and forms a lubricating gas layer between pad and disk, grooves/holes allow the gas to escape, increasing friction.

Grooves are probably the best option for avoiding cracks, make sure grooves have radiused roots. Curved van rotors will also help prevent cracking (this is the primary purpose of the curved vane).

Paul


[Edited by Pavlo - 7/1/2002 11:57:01 AM]

What are the pros and cons of having discs grooved, crossdrilled or a combination of both ? Not just in terms of ultimate performance but what about pad wear, noise, potential cracking etc... Not into track days (yet!) just for fast road use ?

BTTT

Drilled discs might look nice, but are prone to cracking. Drilling offers no performance advantages over grooves. And try to get two-piece discs which offer several advantages (separate alloy bell, not cast integral).

Richard.

Thanks Hoppy.

Drilled disks may look good but if you use them in serious anger (read - track day) they will crack with potential disasterous consequences. I had a set of Cossie drilled disks on the RS Turbo and these lasted one Donington and one Castle Combe track day.

jon

http://www.turbocharger.co.uk/

Cross Drilled and Slotted Combo rotors are good for street use only. The drilling and slotting with give better pad bite than standard discs especially in wet weather. The more slots and grooves in the disc, the more pad wear you are going to get. This is the compromise for deglazing the pads.
For Track use, the critical moment is the first 6 to 8 seconds of braking when heat load is at its maximum. This energy is absorbed by the rotor's material mass. The Cross Drilled rotor with less mass and surface area because of the Drilling and Slotting will generate more heat than a slotted or standard discs. This extra load will fatigue the iron much quicker and result in cracked discs more often. This is one reason why slotted discs are more suited to track use, the other reason is to avoid glazing of the pad and rotor which cannot be done with a standard rotor.

Regards
Steve

Cheers guys.