Rich Sandor

Gordon, I have to agree with Sam.

If you can lock up your brakes before the fastest corner of any given track, you have enough braking power. At that point, bigger brakes will only reduce the fade. If you want to be able to brake harder without locking up you need more rubber, not more brake.

And as Steve wrote above, I've heard people say that bigger Master Cylinders only reduce the amount of force you need to apply to the pedal - and doesn't really add any more braking power either.

Have you thought about adding more cooling to your brakes? You say it's well ventilated, but is that only incoming air, or do you have a system setup to vent out the hot air and make room for more incoming cold air? Someone on this list had some really trick modified fenders with huge Carrera GT style fender vents on them.

Sam Lin

DrRon, what specifically are you wanting? Be specific and identify exactly what you want, otherwise you'll be left chasing something impossible. Then we can advise you better.

Sam

gmonsen

Rich,

Let me be clearer on the braking issue. If the stock brake setup locks the front tires at, say, the entry to a corner and full breaking began 500 yards earlier, a bigger rotor and stonger caliper braking setup might lock its tires with full braking beginning, say, 350 yards from the same lockup point.

Also, when you go from, let's say, big stock brakes to racing/larger afermarket brake setups, you often need a bigger master cylinder to be able to actually work the calipers correctly and deal with the larger mass of the rotors. Generally, as you upgrade systems, all the major parts need upgrading to a like level. (What I mean is, that when you upgrade fuel injectors, you may upgrade the fuel pressure regulator, fuel line sizes, and eventually, the fuel pump. I believe the same holds with brakes.)

Gordon

gmonsen

(uuhhh.... I kind of like the "full breaking" thing.)

Gordon

whakiewes

I have been browsing these boards for some time now, but just decided to give some input.

My girlfriends father has a built Beetle. The beetle has somewhere in the range of 500awhp thanks to HPA Motorsports. The brakes used are GT2 calipers on standard metal rotors and custom hats. The rear is also from a GT2. The braking is quite phenominal. My only experience with Big Reds are on BMW's, so it was different. Where as I would enter a turn at 100mph on the track, I would start braking at the 200m mark to be down to 50 or so mph. In his car, 400lbs heavier from 120mph, he kicks the brakes at the 100m mark, yet we are both at the same speed entering the turn. I can make 5-6 laps before fade is to dangerous to continue, he can go all day. My experience with big reds is about the same. The car I drove was a 452rwhp M3 with big reds up front and out back. Stock M3 brakes last about half a lap before they just are useless. With the big reds, there was no increase in braking force, it enabled me to drive 6 or so laps before I warped two rotors. My opinion on the matter comes down strictly to techonology...big reds are 2-piece older style Brembo calipers, where as the GT2 brakes are Monobloc 6-pot Brembo calipers with 10 more years of techonology in them.

Another option, which I never though about was the standard Cayenne calipers. HPA built a kit for my girlfriends Audi A4. The calipers are similar to the GT2 calipers, Monobloc 6-pot. The difference is the piston sizing. The GT2 brakes use a piston diameter suited for the GT2...which includes HUGE rear brakes as well. The Cayenne uses a smaller piston diameter, more suited to our rear brakes...well Big Red rear brakes. In her car with stock rear brakes, I can go forever before I feel the slightest bit of fade. The pricing isn't bad either, slightly more than big red calipers ($397/ea list) at $462/ea list. The GT2 calipers are $964/ea list...if anyone has thought about purchasing new ones.

One falacy I see is in the master cylinder. The total area of our old style Brembo calipers (86' style) is actually more than in the Big Reds, but less than the GT2. Our stock master cylinders actually create too much force on Big Reds. While they are larger, the piston diameters aren't much larger at all, and the over all area for the fluid to fulfill is less. GT2 brakes would/will require a new larger master cylinder in order to see the actual force exerted by the brakes. The Cayenne calipers I am not sure of, as I don't have the piston diamters, but next to a GT2 caliper they are quite a bit smaller. To that note, the stock master cylinders on our cars are notorious for going bad, so replacing with a larger M030 unit wouldn't be out of the question for me just as a preventative measure.

My opinion that if you are not satisfied with the pedal feel of big reds, you will hate the GT2 brakes more. They are meant to be raced, and have A LOT of clamping force. The big reds are old techonology though, and if you look at it that way, they are outdated. If you are going to be buying new OEM parts, spend the money and purchase modern techonology. As for the 996 TT brakes, Ian Klass has a one off kit. I don't know much about it, but have seen them in person, and they look good. The stock TT is a monobloc 4-pot design, using the identicle sized piston diameters as the big reds, so that seems like a very good option.

DrRon

The current brake setup is pretty much standard, with drilled discs, and plenty of air to and from the discs - the Pagid Orange blocks take about 1.5 laps (approx. 4 miles in racing use) to heat up, and then usually last well for the race distance distance (approximately 20 laps) - a very slight fade sets in after 8 or 9 laps, and this is particularly noticeable when - coming from a straight where we can hit about 135 miles per hour, we need to come down to about 65 mph. Hitting the brakes at the 100 meter mark is ok for the first so many laps, but this gradually needs to increase (don't ask how I know - gravel pit) to about 110-115 meters, sometimes 120, in order to scrub off enough speed.

The impression I have is that we cannot get the wheels to lock up - we run with ABS, and it will never activate at the end of the straight. Compared to the RS's and RSR's, we need to be on the brakes about 20 meters sooner - so, under ideal circumstances where they have no fade, and brake as hard as they can, we typically lose 30-40 meters of topspeed travel before that turn. So looking for harder braking and completely fade-free - bigger calipers should be primarily responsible for the first, and those and bigger discs for the second. The fact that we should be upgrading the turbo next, mand will thus carry more speed on the straight, makes it more important that we look at the brakes.

whakiewes - that is very interesting information about the use of the GT2 brakes on the beetle, confirms that they should be able to achieve what we want. We realised that we need a much bigger master cylinder, to drive the much bigger calipers - the car is full race only (not sure the national police wants to see a be-winged 951 on the roads...).

Everybody - I hope the above clarifies what we want to achieve - strictly racing issues, for normal road use the standard brakes should be just fine....and the offer that we have is very tempting.

Eyal 951

I was wondering if cayenne brakes can be used. I looked at them on a cayenne the other day, and, like many of us have thought before "I wonder if those would fit my car"
Go for the GT2 brakes if you have a good deal.
~Eyal

whakiewes

The Cayenne brakes will work same as the GT2 brakes. Just like all Porsche kits, the mounting holes are identicle to GT2, Turbo 4-pots, etc... If you are REALLY intersted in one for your 951, I can arrange to have several 3-5 kits made at a slight discount. I am interested in one myself, and I have been discussing talking to Marcel at HPA and having him make me custom brackets. The only downside is due to the size of the calipers, and needed rotors, 17" wheels are miniumum, and unless you update to the 88+ fronts, you will need 10-20mm spacers depending on wheels.

DrRon,

The clamping for on GT2 brakes is obviously quite phenominal. Infact, comparing a GT2 in which I rode in today, to a 360 Stradalle, it makes the 360 feel like a kids toy. I am not sure what your rear setup is, but after driving my girlfriends audi with the Cayenne brakes up front ONLY, the braking is very front biased. The back end gets VERY twitchy under threshold braking. In racing situations, you can't have this happening, unless you wish to ruin yours, and several others weekend. If you are looking for an ideal brake setup, I would attempt to use 996 TT calipers. The are the same one-piece design, but utilizing the square area of 4 pistons vs. 6 pistons, you can find better rear brakes for less and still maintain a balanced brake setup. I feel that with 996 brakes, you should have MORE than enough power to lock up the brakes, but locking up the brakes is also very bad. Any racer knows that fade is the enemy, so I think that you should be fine with 996TT calipers, Steel GT3 rotors with custom hats, and a good set of pads. Brake fluid is also a concern when upgrading brakes, so finding the highest boiling temp fluid, with the best feel is also key to a good brake setup. Also with the 996TT calipers, you have a much larger choice of brake pads. Those, followed by a big red rear or possibly stock 996 rears should setup the car nice. Then again, you shouldn't be relying on ABS in a race, threshold braking is the key...the point just before an impending lockup, but not activating ABS...that is the place where braking performance is optimized. ABS units can fail in a race, resulting in an off-track excursion; too many off-track excursions in one season can result in probation in the next season. Ask me how I know .

Wes

DrRon

hey Wes,

Agree - lock-up is not what you want, and neither is ABS cutting in. The ABS on our car actually works quite nicely - you can brake very hard before it cuts in, and the only times you can feel it working is when one side of the front becoms light (in slow corners with a bit of a camber, and braking into the corner). We have debated whether to have a switch to disable the ABS - nice to have it in the wet (we live in Holland!), could do without it in dry, and definitely do not want ABS when you spin the car).

The set that we were offered is a complete GT2 set - front and rear calipers and discs, and would require custom brackets, master brake cylinder and bias valve - what made me start this thread is that the asking price is probably lower than what a set of Cayenne calipers and suitable discs would come to.

In terms of wheels we should be fine - we run 18", 235 front, and 275 rear - may need to get wider tyres to increase the braking surface....

Keep the advice coming - we need to make up about 6 seconds on a two minute lap to catch up with the 993 RSR's (I know, a smoother and quicker driver might do the trick....) and the GT3's are a little below that.

On your girlfriend's Audi - would a brake bias valve help out?

BTW you drive some nice cars! BMW with over 400hp, GT2, Stradale....