Mr Kleen wrote:Overpowered front brakes can actually increase your stopping distances. a lot of the science behind building a good brake system is counter intuitive. Grassroots Motorsports and Car and Driver both ran articles about upgrading brakes in the past couple years.
There is some benefit to bigger front calipers and rotors. The initial bite and hold on larger brakes (such as Brembos) is noticeably better than on the stocks. If your trying to scrub 30-40 mph in a hurry the fronts do most of the braking (close to 85%). The larger fronts will make a big difference in that case. The problem lies in balance. In a straight line the larger will be better with all other things being equal (rotor thickness, venting, same pad material and wear, etc.) However, the difficulty comes from trying to balance front to rear bias, weight transfer as well as traction to the drive wheels. On a FWD car the fronts are pretty much all that matter. The rears can help keep the rear planted but by and large they are not doing a great deal to help "stop" or "steer" the car. A RWD it is far more tricky. An overly biased front braking system can cause a RWD car to become very tail happy in any braking situation as the weight transfers from rear to front. Add steering into the mix and it gets even more complicated. AWD cars are a mixed bag and there are very few hard and fast rules that will apply to all makes and models. The WRX is an interesting case in point, the Brembo package on the STI is significantly larger than on the 02-05 WRX. The front Brembos are 326x30 vs the WRX 294x24 (over 10% larger and 25% thicker) the rears are 316x20 vs. 266x10 (nearly 20% larger and twice as thick). Draw what conclusions you like. The STi may be more rear biased based on it's dif, and perhaps the larger rears help balance that.
In a write up some years ago in
Sport Compact Car when just a set of front Brembos were thrown on a 02 WRX against a 04 STi the braking distances were remarkably similar, and neither had issues with fade. They actually used the same wheels and tires to keep everything equal.
The
Car & Driver test only did front brake kits (2 Brembo, Stop tech, Prodrive and Hawk HP Plus pads) They all showed improvement over stock with the bigger kits having less fade. The Hawk pads were an impressive upgrade for $130.
I haven't read any specific brake tests that
Grassroots Motorsports did on the WRX. But I'd be very wary of applying a test of one car directly to another, especially if they are different drive set-ups. Even a STi to WRX comparison may not be directly applicable.
I am also reminded of the article I read back when the 06 WRX came out with the 4 pot / 2 pot set-up and one author thought that the new brake set-up may be nearly as good as the STi Brembos. Some months later he did a test by swapping the stock pads to a better grade (Axxis Ultimates IIRC) added some sticky UHP tires and ran it against a stock STi. The results were surprising. From 40-0 the WRX stopped shorter, from 60-0 they were even and at 80-0 the Brembos stopped slightly shorter. The author believed he had vindicated his claim and stated that he saw no reason to upgrade the stock WRX set-up to the Brembos.
At some point I will also grab a set of subaru 2 pot rears.