Just got back from Laguna Seca, where Julianne and I put 330 miles of track time on the M3. The car performed flawlessly, except for those damned ROTORS! First set warped in the first hour, and we just suffered thru the day until we could mount the rotors that I bought from Rich Bisevich (thanks again, Rich). Well, that set lasted about an hour, and now they are warped, too. I haven't heard from Rich, but last time I heard, HIS FLOATING ROTORS were warped as well!!!

Laguna is hell on brakes, that is clear. For example, you go into turn two going down a steep hill at the end of the front straightaway, going at least 90, more like 120 if you stay on it and don't lift at the crest, and have to bring it down to 65, double clutch into 2nd, and out of 2 at 60+. Then lots of brakes for 3, and then again 5. Some at 6, and TONS of binders before 8 (the corkscrew), unless you are Alex Zanardi (seeing it in real life makes you think that Zanardi really is nuts!). After rocketing down the hill from the corkscrew, you brake hard for 10, then almost stop for 11. I don't think that anyone there this weekend got thru it without warping their rotors.

I am now convinced that unless you really modify your stock M3 brakes, or even upgrade to something bigger, they will warp on a really tough braking track like Laguna. We have talked about pads (I was using Hawk Blues), and have talked about the floating rotors. Assuming that we have the correct race pads, and floating rotors, what else can we do to avoid rotor warpage? Terry Donahue said this:

Date sent:        Thu, 17 Oct 1996 00:15:47 -0600
To:               buckland_at_xmission.com, bmw-performance_at_xmission.com
From:             donohue_at_azstarnet.com (Terry Donohue)
Subject:          Rotor Warpage-corrections and updates

Send reply to: bmw-performance_at_xmission.com

Just a few additions to our earlier comments on rotor warpage and brake performance:

1. I've been running ducting on the M3 for 2 yrs, so this wasn't a recent improvement. The improvements in braking had to be a result of either the floating rotors and/or the Hawk Blues.
2. My ducting is extremely effective, where the hose goes right into the center of the rotor, and is well protected/baffled by the partially cutaway backing plate. I tested the system by directing a leaf blower at the front air dam, and the "spray" of air coming out of the vented rotors is really impressive. Think of what it is like at 100+ MPH. (snip)

Terry Donohue

Terry, I told you that I would do the ducting, but I didn't, and now I am paying. Please be specific about how you did the ducting, and I wil do it before Sears Point on Nov 16-17.

By the way, a mechanic who works on the Richie Hearn CART car helped me change rotors, and he said, "these air vents look great, but why didn't BMW put ducts from the front air dam to the center of the hubs?"

Further, he (the mechanic) said that my rotors were put on backwards!! The floaters are clearly marked left and right, but the original rotors are not. The vents on the outer edge must face BACKWARDS, to vent the hot air away, rather than forward, "to scoop up air." the design is to bring the air into the center, then it blows to the outside. Sounds obvious, but it wasn't to me or my (otherwise very competant Salt Lake mechanic), nor was it to almost every guy I posed the question to in the pits---at least half thought that the rotor veigns should face forward. If you are one of those, be forewarned. Check yours, lest they be on backward.

BTW, the second set of rotors were put on correctly, and they warped anyway!

So, here are my questions:

1. from whom should I buy the floating rotors, and how much should they cost? I talked to a well known West Coast tuner, who wants $395, plus 2 hours install. Sounds "a little steep."
2. Terry, please describe your ducting
3. any more suggestions?
4. has anybody gone to a whole new, bigger brake set up?

thanks for the imput,

Carl

Carl R. Buckland
1000 Boston Bldg
Nine Exchange Place
Salt Lake City, Utah 84111
801-531-6686
Fax 531-6690
E Mail buckland_at_xmission.com