Try upgrading your pads and REAR brakes (archive)

I have had M5 front brakes on my 535i since 1998. The kit I got had some trick stainless rotor hat covers. I think these were/are available from CNPR. I bought the setup from a guy who originally got it from Dinan, so maybe they have them, too. I took the car to Roebling twice that summer (1998), and I was outbraking everything in my group from 120MPH. It was 95F with blazing sun all four days. Those same rotors are still on the car with no signs of warpage and very little wear. The pads lasted all four days plus another 35k miles or so, and were replaced last week only because one of the calipers was beginning to seize.

My point is this: Try cooling the brakes better to keep them from warping. The hats take air from behind the rotors and direct it into the vents. Removing the backing plates will help, too. After two years of street driving, I've never had a problem with wet brakes unless I drove through a deep puddle.

Anyway, as for the upgrades, try Hawk HPS pads all around. I have them on my M3, and you barely have to touch the pedal to feel them slowing the car. Also get E34 rear calipers, either vented (M5/540) or unvented (525/530/535). Barry from bimmerworld installed the unvented rears on my 535i with Hawk HPS pads all around. He said it is one of the best stopping cars he's ever driven, and that includes many different race cars! I think my M5 has factory pads all around (lotsa black dust), and it doesn't stop for shit. The front brakes are 300mm with a huge swept area and four pot calipers. That's plenty. The E28 rear brakes, however, are a disgrace: 284mm with a tiny swept area and small caliper piston. E34 rears are only one piston, but it's much larger and the rotors are 300mm diameter. You get a huge increase in piston size and swept area. If you track your M5, then you should get the vented. Otherwise, you're just adding more weight and wasting money. The front brakes of a stock E28 M5 do about 88% of the work. That leaves you with severe nose-dive, more stress on the front suspension components, and greater heat build-up in the rotors. Upgrading the rears will bring that more toward a 75/25 split, which is closer to ideal for a front-engine car.

And here's some info that may dissuade you from "upgrading" your front brakes: Bigger front brakes weigh more. The larger rotors of the 750iL weigh about 24 lbs each! That's 100% unsprung weight, too. And that weight also sits an extra 12mm out from the center, which results in a greater polar moment of inertia.

So that's why I don't like to upgrade the front brakes. Do it if you want, but you'll only be shifting more brake work toward the front of the car. This will result in faster front balljoint, bushing, and tire wear, and decrease your capacity to trail-brake while entering turns.

Any comments are greatly appreciated.
James
james_535@yahoo.com
88 M5
88 M3
83 535i

Bimmerworld

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