Rainmaker, If you are looking for a real improvement in braking, I will work on the assumption that you:
a) drive the car hard on the street,
b) drive the car in a calm manner on the street, but hit the track on the weekend
c)live in a mountainous area, or one with super curvy,fun roads. (If you live in flaaaat Chicago where I grew up, I urge you to DRIVE WEST !! : )
Taken as a whole, the stock S4 Hp2 brake system is a high performance setup that has several drawbacks for people who "exercise" their car. The first is that the rotors are quite easy to warp in hard driving.The second is that the caliper has a fair amount of flex to it which makes for a grabby feel . Light brake modulation becomes difficult because of this grabbiness. The third problem is that the OEM pads are very expensive to replace.
The poor rotors are the real downfall to the system. Rotor choice is extremely important. As rotors heat up they hit a threshold where thay cannot shed heat anymore, thus your braking suffers immediately. Rotors are what keep you stopping no matter if the caliper flexes from the effort.
Using stock calipers with aftermarket rotors and lines is a band-aid solution that only partially cures the problem you WILL encounter if you take your car on the track or drive it hard on the street. Remember that the B5 S4 weighs in at the scales around 3600 (portly) pounds. These brakes are not stopping a Miata !
I don't buy the argument for a second that people don't drive their car "hard enough" to justify a big brake kit, or what dramaticstatic advises,
"They actually make your car slower with increased rotating mass and may make your stopping distances on the street longer because of the way the car proportions its brake bias. If you're not overcoming the grip of the tires you could go larger but make sure you upgrade the back somehow as well as the front and try to keep everything in proportion."
A kit such as a one piece cast 4-piston Alcon caliper and double heat treated 332 mm rotors weighs LESS than a stock setup and outperforms it by a mile. A well designed kit like this will keep brake bias in check and requires NO rear upgrade to be effective or "balanced". Brake kits are not randomly parsed to any available automobile. Caliper construction, rotor sizing, pad choices are carefully planned in many cases. The same cannot be said for something like a Porsche 993 "Big Red" caliper being foisted onto an S4. Think where the engine and weight lies in each car and you can see why a kit designed for an S4 is the optimal choice. An aftermarket BBK will stop your car depending on the pad choice and the heat in the system, exactly as the stock one will. The difference is that heat treated rotors with stiffer calipers will evacuate heat consistently better than any stock system on the same car. Suggesting that a big brake kit will make the stopping distance longer can only apply to a setup that is cold and has race pads in it at the time, as race pads need heat in them to become effective. (reference: European Car, February 2004, S4 Shoot-Out, brake-off page 44) I am not meaning to imply that the cars brought to magazine shoot outs are "regular" cars, but that you cannot easily spend too much money on great brakes !!!
I would suggest you take a serious look at an Alcon 332mm BBK kit which can be ordered during a promotion that Avalon Motorsports is having right now on suspensions and calipers. The 4 piston caliper is lower profile than most of the competitor's kits; the calipersand the 332mm rotor can clear most 18" wheels without a problem. Most 18" wheels can actually fit over a 355mm Alcon kit.
The 332mm kit is only $2200.00 right now, and can be combined with a two piece floating rear 298mm rotor for only $3000.00
I invite anyone with brake questions to call us to speak about different setups that can be had for the S4 or any other car. I also wish to invite anyone to visit the Denver AUdi club and participate in a club drive at Second Creek Raceway or on our scenic mountain drives.
Many seriously equipped cars at the track have suspension and brake mods and stock power. This can be a recipe for a great performing and not hugely expensive mod plan for an S4 owner.
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