mds

I am looking for help on how to reduce front brake disc cracking. After about 400 track miles, the front rotor cracks are about 5mm long, some are 7mm. The rotors need to be replaced. The rear rotors are fine with very few cracks, all 1mm or shorter.

The brake pads are only lightly worn with 8.5mm of compound remaining the the fronts and 11.5mm on the rears. So pad wear is not an issue.

I've heard it said that it is possible to learn to conserve the brakes and yet still get good lap times. Can anyone explain how to do this?

PogueMoHone

Talk about the Holy Grail!

I'll take a shot, but I haven't executed on this yet.

It's a question of style and technique.

Method A :

Drive like hell and brake like hell (and sweat like hell). That's one style I see a lot, and generally people are in way over their head, and survive on luck, known as the "***** for brains" approach

Method B:

Drive a little slower, brake less for speed reduction and more for car balance and positioning, and gradually work up to more confident and faster lap times. It's building on fundamental skills.

This is easy to write but very difficult to implement..hence the Holy Grail. So know you know what I'm doing and thinking about when I'm out there. The success level is another matter.

Replacement rotors $750 a pop, but you should be getting about 2500 track miles out of them. I'll be interested to see if you dealer will replace them under warranty.

brh986

One important technique is to learn threshhold braking and learn it well. As soon as you get on the brakes get on them right to the limit and then come off them as soon as you've sufficiently slowed down.

In street driving you usually do the opposite. You see a red light far off in the distance so you ride the brakes lightly, not sure if it will turn green before you get to it, then if it doesn't you apply them harder or even slam them on depending on the situation. This isn't good as you've already started to heat up the brakes by riding them lightly first. This isn't good on the track. Unless you're in a situation where only a tap on the brakes is called for to balance the car you should really be threshold braking for maximum stopping power over minimum time.

I don't know how much difference this makes in practice on the track but it sounds good to me in theory.

mds

Colm, there is a cheaper source for rotors. PM me.

A lot of people jump on the brakes very hard. I was always a guy who braked, for the most part, very easy. I didn't use up the brakes at all since I tended to roll off the throttle and onto the brake more easily. To put it in perspective, at Laguna Seca, which is hard on brakes, Rick Mears and I were teammates at Penske and Rick finished the race with only 70 thousandths of an inch of brake pad material left. I only used 70 thousandths of the pad in winning the race. People brake differently but can still run the same lap time, especially in a race.
- Danny Sullivan

Greg Fishman

I hate to ask what would seem to be an obvious question but.... Have you considered adding some extra ducting to the eye of the rotors? Maybe some parts from the 996 GT3 Cups cars or something custom?

mds

As far as I know the car already has Cup car ducting. If its good enough for the Cup car it should be good enough for my car, no? I must be doing something wrong.

bob_dallas

What pads are you running? Are you doing a good warm up lap or two with light braking and a cooldown lap with mnimal braking? I just checked mine and no cracks and no baked pads as I previously thought - must have just been a piece of trash between the pad and rotor that was making the sound. Not sure how many track miles I have but probably around 400 as well...

Steve in FL

Mike: Are you following the Danny Sullivan approach or do you favor the hard braking approach? I know changing to the former greatly prolonged rotor life on my 911T and those weren't even cross-drilled.

Greg Fishman

I bet it is different as the Cup car system limits your turning lock. What you want is a cooling duct that goes from the front of the car all the way to the eye of the rotor. Is this what you have?

From this thread the "ducts" are more like scoops that guide air into the area vs. ducts that force it through the rotor. https://rennlist.com/forums/showthre...+cooling+ducts

mds

Greg, there are no ducts on the car. Just two scoops, one redirecting air up from under the car and the other inward from the side radiator exits. I will check out a Cup car and see what is different. Thanks.

Steve, I have been trying to transition into and out of braking smoothly and also trying to stay out of ABS.

Bob, Pagid RS19. Yes I have been doing a warm up and a cool down.

Karl S

Greg & Mike,

The Cup car uses the same two-piece duct system as the street car for front brake cooling. I ran a hose-based system like Greg describes on my 996 but was told by the owner of a Grand Am team that the small hose diameter (3") actually limits air flow to the rotor and that the Cup/GT3 system gives superior cooling.

Karl

Steve in FL

Weird, the RS19 pads are supposed to be gentle on the rotors. Here's another thread from funcars on the iron rotors cracking: Rotor cracks thread. This guy was trying to out brake Cup cars so his brake abuse level sounds much higher than yours Mike.

bob_dallas

Interesting that you are using the RS19 - that's the one I was thinking about trying out next. They are supposed to be easy on the rotors but it's hard to tell as you say if it's your braking technique or the equipment.

WRT your question about technique making brakes last longer I'm afraid that's a pretty complicated question and varies by track and turn type but there are some good general rules. If you don't already have the Skip Barber book "Going Faster" I'd highly recommend getting it - chapter 5 has some great braking information and an in-depth discussion about using less braking to go faster. I've read this book countless times and learn something new each time.

Greg Fishman

Interesting, since the 993 GT2 and RSR used a 4" duct directly to the rotor with a shield to force all the air through the rotor. I would be interested to see what the GT3RS(R) uses for brake cooling.

macfly

This is just a random thought, but last year I went thru a very long brake development cycle for a larger better brake system for the Z8 with StopTech, a really great SoCal brake company. They supply the factory Viper GTS race cars with their brakes, and make many other after market kits http://stoptech.com/

These guys are dead against drilled rotors, far prefering the slotted disc as it dissapates gas and water faster, gives more friction surface area, and doesn't crack. I haven't suggested this to them as yet, but if folks are eating rotors enough I would suggest we could put together a group buy, with enough interest I'm sure they would make up some slotted rotors for us.

The website also has a really well laid out series of articles on braking, and can make for some informative and educational reading.