Gang,

I like what Hunter has said about the big brake upgrade but remember this. He is talking about a Porsche here. Yeah you could genalize some of it to apply to an M3 but not all of it. What about the upgrade to a BIg Brake Kit? On a Porsche, why would you want to upgrade. It is like Greg said in that the 928 uses the calipers of a 993 Twin Turbo. I cannot fathom why someone would want to upgrade but I know that people do. I have the Porsche kit on my car and I can tell you that the car feels well balanced during braking at the track and on the street. As for a 928 being similar in weight to our beloved M3's it might be but there are some major differences that can affect this braking balance. One of them is that the 928 is lighter in the rear than our M3's causing more of a need for a biasing kit. One thing that you have to remember about the M3 and the Porsche is that the M3 has a braking deficiency on the track and the Porsche does not. The M3 loves to cook the brakes after a couple of laps. Put on a brake kit and now your problems are fixed. There are plenty of people running one kind of brake kit or another on their cars, and most of them have never had a problem out of them. They also do not have the problem of cooking the rotors again. Do this if you want to see what the difference is: Take a pyrometer and measure the temps of the M3 brakes and that of one of the Big Brake Kits. If you are lazy then you can trust Neil Miller as he has already done this. His findings is the the stock brakes were somewhere in the mid to high 700 degree range and the M3 with the Porsche kit on the front was in the high 200 degree range. Now tell me which is bad for our cars. Now I also know that this does not mean everything as there are other examples we need to get a firm conclusion here. I do have them but I can tell you that the Porsche kit is the best engineered kit on the Market. The rotors, calipers and pads were all designed by Porsche, the company with the best brakes in the business. What else do you need to say about that!! Now we can benefit from this engineering on our cars thanks to Quido and Movit.

Seth Thomas
www.m3power.com

Gang,

Re brake postings recently, the Porsche Club of America's Panorama magazine has unusually excellent articles about preparing vehicles for the track, and over the past 6 months in particular there have been two articles which were very informative. I suggest that anyone interested in these contact the PCA to either get a membership or at least reprints of these articles. I'm sure I can't quote the article verbatim to the digest, but I think I could give you a few key points the author of the latest article, titled "Braking Systems, Technology and the Track". As someone on the digest pointed out about a year ago, Porsche brakes are perhaps the best production vehicle brakes on the planet (although the Brembos on Ferraris might be a very close second). However, given the weight of production cars, even Porsche brakes often fail in near-racing situations. As background, the author has experience putting his 928 on the track, which is comparable in weight to our M3s (at 3,400 lbs), so I think some of his comments might be worth noting.

1. Re stainless steel brake lines, apparently non-DOT approved lines do not have strain relief ends which would allow the connections to flex (SS brake lines are very rigid compared to the factory rubber lines, which bend by themselves and don't need strain releifs). The author says that he has seen more than one of these types of failures, and apparently race teams replace these regularly. He suggests either DOT approved lines or keeping the stock lines.
2. Re pads, the author runs PF90s on the street (although he doesn't mention the rattling I get when I put them on my M3 for track use). Just another data point. Although there have been uncountable posts re the "best" pad for the track, he adds mentions that going to full race pads will allow the pads to put severe thermal stress on the other braking components (most importantly the rotors). For example, he tested pads with an CART style compound which required only two laps to generate enough heat to crack the rotors. But there's no doubt that street pads (that is, softer compounds) do not help, either -- he cites a test of one street pad which, after 20 laps, was worn from new to backing plate.
3. Re rotors, after putting in ultra high performance (and fresh) brake fluid and good track pads, the stock rotors now are that much weaker than the rest of the system and thus that much more prone to failure. One tip he gives is that new brake rotors need to be "bedded" [my quotes] in just like the pads; 150 to 200 miles of regular driving before tracking the car helps put the rotors through some heat cycles which apparently are needed to further heat temper the cast iron rotors. Otherwise the rotors wear much faster.
4. Re big brake kits, the author says that in some of his tests, upgrading the front brakes alone can lead to MORE front brake failures (!?). As I have questioned re big brake kits, the author states that when the brake balance is disturbed (by adding more braking torque on the front, for example), the front now starts to do a lot more of the work, and the rear is underused. Porsches apparently have fixed pressure regulators on the master cylinder or ABS unit which can be quickly swapped out to readjust the front/rear brake balance. For example, the author, after upgrading the front brakes on his 928GT, removed the 18 bar (265psi) rear limiter and put in a higher unit (they range from 18 bar to 55 bar, the higher for more rearward weight bias and thus more rear brake bias). By doing so he says that the difference between front and rear rotor and pad wear was reduced, and the heating of the front brakes was greatly reduced, along with stopping distances and changes in pitch. I have always wondered how you can get by with installing huge Brembo rotors up front on an M3 and then expect to have proper, efficient braking balance. According to this guy, you can't, and the adage "most of the braking work is done by the fronts", while true, doesn't really address whether the car is stopping efficiently or safely (if additional pitch is introduced).

An excellent example of why brake balance front to rear is key is Michael Schumacher's wreck at Silverstone. Pictures in German magazines clearly show that when his rear brakes failed, the front tires were locked and worn through the cords, while the rear tires were in perfect condition -- he didn't have rear brakes, and his car wouldn't stop. Clearly your M3 doesn't depend upon its rear brakes as much as Schumacher's Ferrari, and if you lose half your braking system you'll crash too, but the fact remains that you can't ignore front/rear brake balance after making brake modifications.

Given that some have posted recently that they buy $100 sets of front rotors, it seems to me that replacing 6 sets of rotors every season is more cost effective (over 5 years) than buying a $3,000 big brake kit, which its extremely expensive rotors which will need to be replaced every two years anyhow. One of my acquaintances in Germany knows some insiders at BMW Motorsport, and one of my goals while I'm here is to come back to the US with the absolutely best braking system available for my M3/4. I'll let you know how I make out.

Hunter
1998 M3/4, PF90s at all four corners on the track, and polyellipsoids at night.