Cass944

i have a friend named tim that has a strictly track driven 944 out at our local airport. the entire body except the unibody is carbon fiber, no interior, coil overs front and back, 996TT brakes dual master cylinders, THE WORKS. He still was not satisfied with his brakes so he told me he wanted cast aluminum because they would save a few pounds of weight. well the thing is that they dont exsist. so i guess he paid some company for the development and engeneering of them just so he could have them. so now he has the shiniest most amazing looking brake rotors sitting in the back of his darango out at the airport. I dont have a picture but ill get one when i go out next week.

so is this true that these things didnt even exsist until he paid this company to develop them?

I kept thinking he actually said cast iron but that woudl weigh more wouldnt it. Im pretty sure they are aluminum.

either way they look really freakin awesome

Fishey

Aluminum is very light (and strong) and it can dissipate heat very quickly. However I do think that they will run into warping problems with the rotors as aluminum under heat tends to bend

Peckster

There's probably a good reason why he couldn't buy them. It may be light, but it's also probably too soft for this application.

M758

Aluminum melts at like 1200F vs steel at closer to 2000F. Not a good brake material. F1 and protoype road racing could use anything for brakes. They have two choices. Steel and carbon-carbon. No aluminum.

mrmunky

hey brett check it out my front end is about to look like this:

mrmunky

and this

Danno

Actually steel melts at over 3000F.

The issue here is heat-capacity. For any given braking distance and speed, say 60-0 in 125ft, you have to convert a certain amount of kinetic energy into friction and dissipate it as heat. Since aluminium has a lower specific heat than steel, for any given heat input, it will heat up to a higher point than steel.

The 3x faster thermal conductivity of aluminium won't really help it shed that heat faster than steel, because the rate-limiting step is the air around it and how fast that air sucks up the heat and how fast that air moves away from the rotor. The air around the rotor will behave the same so you'll get similar heat dissipation. Now, if he were to make rotors that were much larger than stock, such that they have more surface area to radiate heat to the surrounding air, then there may be some benefit.

I think he'll have a very interesting experiment on his hands. One thing that he may not have considered is the heat generated at the contact surface itself when the brake-pad presses down. I think I'll find major streaking from the rotors as melted aluminium gets smeared around...

Now what you [i]can[/i ]do with aluminium, is use it as a binder to hold a tougher material in an MMC matrix. Like the CoolTech rotors from 6-7 years ago that was an aluminium/silicon-carbide MMC. Weighed just 1/3rd that of cast-iron. Compact Car mag had a review of them on their RX-7 project.

Cass944

ian wtf is that, it looks like something off of a old talon

xsboost90

me no likey the nosey....

how bout some ceramic rotors like the gt3?

Mongo

IMO I think I'd sue the surgeon

Andy

Danno

"how bout some ceramic rotors like the gt3?"

Aren't those failing like crazy after 3-4000 miles?

M758

Yep...
Lots of GT2 & GT3 guys are claiming they they have ruined $15k worth of the PCCB brake rotors from just a few track days. Heck they are swapping pads like crazy to find one that work. Lot of them think the PCCB is not quite ready for production yet.

FWIW... There there type of brake rotor materials
Cast Iron = Use most commonly in everthing from race cars to cheap street cars.

Carbon-carbon = Typically used in F1 and Audi R8 Le Mans Prototypes. Hugh advantage vs steel (cast iron) in terms of heat capacity and weight saving. Hughly expensive and requires lots of heat in the system to work. They hardly stop at all when cold.

Ceramic blends = PCCB, Ferrari also has something too. These are ment to meet 3 goals, 1 weight reduction and performance better than steel approaching carbon, Can be used effectivly cold as this is critical for street cars, and is somewhat cost effective. It is tough to get all 3.

Luke

That's more realistic. The lower carbon steels i've seen usually melt around 2800-3100.

Peckster

Looks like a pig nose. oink oink

Danno

The 1st-generation European-spec Lotus Elise, the one with the Type-R motor, had some sort of composite/MMC brake-rotor as well. Haven't been able to find more details on it though...

One cool thing that may be on the horizon, maybe far, far horizon is a metal foam. Take cast-iron or steel and whip a lot of air into it, like a chocolate mousse. This lowers the density and makes the part lighter. Strength isn't compromized too much depending upon the size of the air-pockets. Of course, this requires zero gravity so that you don't settle the air out of solution. This would make for an aggressive lightweight rotor. Probably would wear out twice as fast for the 1/2 the weight.

Anyone have a picture of that Aerogel or some such thing made from silicon foam? Mostly air, and they had a picture of a hand holding a block of the stuff. Then a blast from a torch was heating up the top side to glowing red, but the bottom side on the hand stayed cool.