I had several concerns about this kit, when I decided to use it:

1. How heavy it is compared to a true big-brake kit?
2. The rotor is only 25mm versus 30-32mm for a big-brake kit, which means less mass and smaller vents for cooling. Would the rotor warp from overheating?
3. Would it fit under my 16" wheels?
4. What would happen to pedal travel and pedal feel?
5. How will braking be affected?

Not surprisingly, the A8 rotor weighs 3-4lbs more than the other brake rotors. The extremely light Porsche caliper helps make up for it, though. Overall, I drop 2lbs per side by going with the BIRA kit, however more of the brake mass is rotating mass. In comparison, a true big-brake kit with two-piece rotors and aluminum hats would probably lose ~8-10lbs per side, and the rotating mass would be part of that reduction. So, one of the trade-offs of the BIRA kit is a smaller reduction of unsprung weight than a true big-brake kit would afford. Since I am still losing weight overall while gaining a significant increase in braking power, I am satisfied with this cost-performance trade-off.

My second question has to do with the width of the rotor, 25mm (versus 30-32mm for a full-on big brake kit), and the resultant cooling (or potential lack of cooling) effects that may occur. So far in my testing I have not had any noticeable problems with the rotors, and that includes several 90-30mph stops in quick succession and also several 60-0 stops in a row. The brakes worked beautifully each time and had no fade at all, but I have not yet driven with these brakes on the track, so I plan on monitoring them carefully at the next event. Again, the smaller width rotor is one of the compromises of a less expensive system.

My third question involved fitment with my 16x7.5" ET35 TSW Hockenheims. Unfortunately, my fears were realized when I found that the Hockenheim design did not have enough RADIAL clearance for the caliper. Axial clearance to the spokes was fine, but the Hockenheim has an especially large internal "lip" which just barely rubs on the caliper. To run the Hockenheims, I can use 8mm spacers to clear the caliper. Instead, I chose an alternative method, buying a set of urS4 16x8" ET40 wheels which also clear the caliper and provide the additional benefits of greater width and lighter weight. It seems that many 16x7.5" ET35 wheels do fit, and my Hocks are an anomaly.

Based on my calculations, the BIRA system should have reduced pedal travel and required slightly higher pedal pressure to actuate the brakes. This result has proven correct, and I am very happy with the pedal feel. The brakes actuate after very little pedal movement, and the pedal pressure required to activate the brakes is not nearly as light and numb as before. They are still not as wonderfully tactile as my vacuum-based Coupe GT, but I am no longer bothered by the pedal as before. Please note that these results may vary by car, as the single-piston conversions may require slightly more initial pedal travel until they bite. I have no direct experience to comment with, though.

Lastly, how would these brakes improve (or reduce) performance and usability on the street and track? After driving with the brakes for two weeks, I can say that I like the brakes immensely. If I had to use one word to describe these brakes, it would be "modulation." With the G60 brakes, I could lock the brakes or not, and that was it. On the 4-piston setup, I can actually get the front tires to howl right on the threshold of lockup without going over the edge...and this is at 80mph! The brakes are extremely powerful and very easy to modulate, and should really help on the track.

And what are my reservations? Well, the biggest concern I have is the extreme frontward bias that the braking system experiences. This is not the best for maximum braking in a car without ABS. Some people have added an adjustable bias valve to compensate, but I may try larger rear brakes first. Perhaps the ABS-based cars are not as affected by this problem. The other concern I have is the price and availability of different brake pad compounds, however that has been alleviated somewhat by Paul Weston & the pads he offers. I am currently running the stock Porsche Boxster pads, which are EXTREMELY dusty and squeal a tiny bit at very low speeds. I do not mind the squealing, but the dust is horrendous, so I may switch the pads in the near future.

One note on fitment of the bracket, I did have to grind some metal off of one bracket to fit one of my struts. Both brackets fit the other strut perfectly, so I believe it must be something about the manufacturing tolerances of the strut. The metal I had to remove was in a non-critical area of the bracket closest to the CV joint, and I felt comfortable with the mod. I doubt that any of the newer cars would have the same problem.

So what is my overall judgment right now? I am very happy with this brake setup, especially given the sub-$1K price I paid for it (my thanks to Didi @ Carlsen for some great prices). For my car and my budget, it was absolutely the right choice. I could certainly have paid more money and gotten a few more benefits, but this setup gives me all the braking I can possibly use on my car and I still have $$$ for other things like suspension. Plus, they look _really_ cool. ;-)