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Date: Tue, 24 Aug 1999 23:37:51 -0600
From: "Carl Buckland" <>
Subject: [E36M3] Re: PF90 question (Rambling)

Kirk says:

>I just finished my first track event with some PF90 pads. While I
>experienced no fade and really good wear, I did run into the *are
>the rotors warped or is it the pad* issue.

Neil says:

>PF90s really REALLY don't like slotted rotors. So I use my
>slotted former track rotors for the street, and plain ones for the

I completely agree. The red goo that PF 90's leave on the rotors needs to flow smoothly over the rotor surface. Slots and cross-drilled holes seem to fill up with the stuff. I have had less warpage with plain stainless steel rotors that I have had with cross drilled, gas slotted, or cross dressing rotors.

Euro floaters are fine, but not worth the extra money, IMHO.

I use the cheapest rotors that I can find, and change them as often as I hear the slightest shudder. I clean them with brake cleaner (also good for cleaning the balancing weights off your rims), but by the time that they are really goo'd up, they are heat fractured (clearly visible), and starting to warp, anyway, so I throw them behind the garage with all their lost Brothers before them and replace with the now really cheap OE Brembo's. With rotors now cheaper than pads, why bother with the *horror* of warped rotors? They can ruin a whole weekend. Bad brakes is 1/3 of a bad car (brakes/tires/power). BTW, buy an extra set of rotors and take them to the track every time. If you don't need them, you will be the Prince of Goodness to the guy or gal who does. Ask your mechanic how to change them. After the first time, they are easy; easier than pads.

I get my OE style Brembos from BMP for less than $100 for a set of fronts. Rears seem not be be an issue. Your local supplier probably has something similar. Slotted rotors are cool looking, I guess, but I do agree that they are hell on soft pads, and aren't worth the extra money that they cost. For once in my rant, I will say "go stock(like)."

I do have to add this. I prototyped some rotors that were made out of some space age materials, and then heat treated before being machined, and they did DEFINITELY last longer. For the normal track junkie, I don't think that they were worth the (substancial) extra cost. Cooling off the rotors every 20 to 30 minutes does wonders. BUT, if you you need your rotors to work for hours on end, like in endurance racing, I would say that these special rotors are definitely worth it. Private email me if you really need to step up to the plate for these.

One more thing.......two people driving the car on one weekend, combining too much heat and different driving styles, can wreck havoc on a set of rotors. Kirk L., you said that you and Terry have been sharing the car. Julianne and I do as well. I can tell you that the weekends that I have the car alone, or that she drives it more exclusively (like when I am most teaching), and the car, therefore, is driven more by one person or the other, the rotors do much better. It is when we share the car that we have the most problems.

Part of the explanation is simple; the brakes simply get hotter, and never have a chance to really cool off. The other part is more baffling; I think that her STYLE of driving, or *braking* I should say, is so different than mine, that when we hand-off the car, we are handing-off a set of brake rotors that are "set up" for *us,* not the other person. Jule is more gradual; starts braking earlier, over a longer period of time. I, on the other hand, wait until the last moment, and squeeze the life out of the pedal. Each style generates different heat, over different time intervals, and probably different pad material dispersion. I am, I am sure, full of shit, but this is am idea that has held my interest for some time. Anyone have any scientific thoughts on this? ( I can mix a scientifically perfect martini. that is as close as I get the pure science).

Carl Buckland

today, on the way home from work,
I tore a tendon in my elbow trying to
solve a big oversteer exercise. My
wife had no sympathy.

Date: Wed, 25 Aug 1999 00:04:14 -0600
From: "Carl Buckland" <>
Subject: [E36M3] PF Z-rated High Perf. Brake Pads

I also agree with Pest's (get a new handle, Bro'!), take on the PF Z's. I have them on the car now, with the same rotors that I used on the track the past few weeks; they have not disrupted the PF 90 material smoothness, and they are incredible street pads. They work well with very little pre warming, and will last through a hard canyon drive. BUT, you can warp the hell out of your rotors with Z pads, or ANY "high performance" stock pads, if you aren't careful. they are "high perf" because they STOP you, RIGHT NOW. they are NOT rated to take a lot of *continuous* heat.

For high performance driving that even remotely resembles law abiding behaviour, they will work fine, but if you really push them HARD, like you would a PF 90, you may not have fade, but you will likely warp your rotors from massive heat build up. Street pads, even PF Z rated, have a lot of mass, and have metal backing plates. All of this amounts to a big heat sink. Just like track pads, they need a periodic cooling off period, but more often.

As an esoteric side note, autocross pads, such as the Hawk Y- 5's, have pluses and minus's similar to those of the PF Z-rated's. They require very little heat to work at optimum efficiency, but they work because they are so soft. They are also extremely dirty, and can't take ANY heat. Try to make several hard stops, and you will warp your rotors in 5 or less tries. I know. But keep them in their heat range, and they will throw you through the windshield.


Date sent:              Tue, 24 Aug 1999 21:31:55 -0400

From:                   pest <>

To: BMW Performance Digest <> Subject: Re: PF90 question
Send reply to: pest <>

> For those of you who don't want to change out your rotors for each track
> event (me!) you can keep that pad material (transfer layer) in good
> condition by using PF Z-rated pads on the street since they also create
> a transfer layer on the rotors. The judder problem comes from changing
> back and forth between pads that are laying pad material on (say PF90s),
> and pads that are wearing it off (say stock).
> Curtis

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