Air cooling

[91_S2]

I love big brakes as much as the next guy. But for some reason Audi guys tend to think that "bigger is always better". It ain't, but it sure is heavier.

Putting a huge disc and caliper on the wheel is great and gives you a lot of heat sink. It also gives you a lot of unsprung weight and moment of inertia which is like trying to make "The Pig" tap dance in cement shoes. The Pig has enough trouble trying to walk!!

The point is we want enough brake but no more. I suggest that we start thinking about shedding heat using forced air. Air vents are cheaper than Brembos, they are (for the most part) unsprung weight and they are effective.

We should start thinking about cost effective, weight effective braking.

My 0.02 Euros

Rich

[Sweeper]

I've heard from some respective guys that track here in rally. They have said that 330mm disk and 4-6 pots are more than enought.

If you go further , it's just heaver.

[peterp]

I can see your point 91_S2, but you have to admit that the original S2 brakes are cr*p. And no ducting will dramatically increase brake performance.

[91_S2]

Cr*p is too nice a word

I agree completely about the original S2 calipers being cr*p. Nothing good to say about 'em except that they work driving around town.

Just now, I am considering 930 calipers on a 304x32 rotor. I think these will fit under my 16" 5 spoke wheels. I just have to get some measurements and make up brackets.

If these get too hot, I will duct air.

Rich

[Fat Audi 80]

Why am I happy with my S2 brakes? (They are standard) Although I have only had the car ten days, I have driven it fast (but carefully) and they seem fine, it lacking in a little feel. What is actually wrong with the S2 brakes? They are miles more powerful than the ones on my old 80 sport!!

[Stick Insect]

91_S2,

Audi do a disk which is 304mm x 32mm I thin VAGsport mentioned the numbers elsewhere in this forum possibly under 996 calipers.

I have the Avus 16" wheels and will be using 996 calipers and custom brackets from Martin_JS on 314 x 30mm A8 disks.
Audi do a 304mm A8 disk for the USA market I believe.

I have a 993 caliper which is for a 304 x 32mm disk, this may be a better bet than the 930 which is a little old now?

Fat Audi 80 you may have better pads in your S2 which would help. I find the brakes poor on my 20V coupe and I have 50 BHP less than you. I bet you will be unhappy when you cook the brakes for the first time. as someone mentioned in this forum the brake fluid needs to be in top condition so that it doesn't boil and cause the brakes to fade.

David.

[Fat Audi 80]

No doubt no that I have mentioned it my S2 is listening and the brakes will start playing up !

I will keep using them and see how I get on. Maybe its just the newness of them coming from a car with even worse brakes....!

[dan_b]

Hey, FA80 - nice to hear that you had an 80Sport, I had two! Nice to hear that you're enjoying your new S2 as well, what's it like?


Yes, the S2 brakes are better than the "brakes" Audi put on the 80Sport, but they're still appallingly under-specced when you consider things.

The S2 is what, 1.5 tons of metal, with 220BHP minimum. There's a hell of a lot of potential energy in that. The S2 has the same brakes as the bog-standard 1.8 Coupe, a car which has less than 1/2 the power.

Yes, they'll stop you once from speed, but it takes quite a while. Try doing it again though, and they start fading already. There's just not enough capacity in the braking system - not enough braking effort available (discs too small, not enough pistons), and there's not enough of a heat-sink to shed the heat (discs too small, calipers too small, brake fluid not of a high enough spec, no ducting).

If you're on an A-road which has several roundabouts, try driving relatively quickly inbetween each roundabout and braking to a stop at each roundabout. By the 2nd or 3rd one, you'll be fading, your stopping distances will be getting longer. In short, you'll be risking hitting the back of that TIR.

I uprated the brakes on my old 80Sport as they were simply awful!
I will be doing the same this weekend on my S2.

The way I see it - there are two systems on a car that keep you alive, and these should be the best standard you can get.

One is the tyres, the other is the brakes. Get the best you can afford.


Interestingly, the RS2 had the bigger brakes, but also had ducting - Porsche know a thing or two about brakes I think.

[Fat Audi 80]

True!

[Mikes2]

The 304x32 disc is only available on the RS2 so cannot be used on the S2 without major work

The Porsche 930 caliper will not fit inside a 5 spoke 16" standard wheel - personal experience speaking here.