9 replies to this topic

[Greg L]

Considering they are often found on high-end street cars (Porsche 911 Turbo, Ferarri 360 Modena, Lamborghini Diablo, et. al.), why aren't cross-drilled or slotted rotors used in F1? Obviously an F1 car's carbon-carbon brakes provide performance that is vastly superior to that of a street car, but wouldn't drilled or slotted rotors help even more? I wonder particularly because rotors are drilled or slotted on street cars primarily to help dissipate heat (and because it supposedly looks "racey") and since F1 brakes generate such massive amounts of heat, wouldn't a bit of help in heat dissipation be welcome?

[desmo]

The carbon discs in F1 are ventilated but the vent holes are more or less radial. Given the restricted wheel diameters and hence the disc diameter, cross drilling will only mean a decrease in precious swept area for braking.

[Greg L]

Thanks, Desmo!

[david_martin]

The thermal-physical behaviour of the composite used in F1 discs is very different to the cast iron or steel discs used in most road cars. The composite has a very low heat capacity and a relatively high thermal conductivity, so they heat up very quickly and to very high temperatures, but they also can cool down rather more quickly than a steel disc.

The big problem with steel discs is that heat flows from the core of the disc rather slowly - often the cooling rate is controlled not by heat transfer at the disc surface but by the rate of internal heat flow inside the disc itself. Cross drilling vastly reduces the distance the heat has flow inside the disc and make brake cooling far more efficient. That effect would be far less pronounced with a composite disc. There are also a number of potential structural difficulties with building a cross-drilled composite disc.

[swoopp]

One of the most important reasons for cross-drilling and slotting rotors is to keep the rotor and brake pad in contact with one another. When brakes are used heavily, heated gas (created from the heating and wearing away of the brake pad) builds up between the contact surface and can actually float the brake pads. So, cross-drilling and slotting the rotor face are methods of evacuating the gas away from the contact area. Venting the rotors this way is more effective at cooling the rotors.

[RedCarFan]

I was under the impression that the brakes on F1 cars worked better the hotter they got. If that is true, cross-drilling would be a waste of swept-area and a waste of heat.

What was that news last year about Ferrari's ultra-thin brake disc?

[desmo]

RCF, about the lightweight Ferrari brakes, read this:

http://www.atlasf1.c...=&postid=154037

[SlowDrivr]

Grassroots Motorsports had an article about brakes, and said that cross-drilled rotors were useful years back when brake pads outgassed more. Modern pads outgass much less and so cross-drilling is mostly for show and don't help braking.

Champ cars use steel (or is it cast iron? Not CCF though), and they are plain, no cross-drilling or slots.

[desmo]

Actually I believe that CART or "champ" cars do use carbon brakes on the ovals. Anyone?

[Greg L]

Yes, Desmo, CART uses carbon brakes on oval courses this year, steel brakes on road courses.