tw1963

Interesting discussion. Just to add to the mix, in the Volvo 850 world there is a very common problem with brake vibrations. Opinions vary on causes with one school of thought being that the 'warped' rotors are being caused by incorrectly torqued wheel nuts.

Another good site for a bit of reading material on rotors and breaking in new pads.

http://www.pagidusa.com/Pagidusapassenger.htm

Cheers,

Terry

'85 928S

Jim bailey - 928 International

If you ever happen to be channel surfing and see a NASCAR race where they have a wheel camera you will see the rotors turning red hot on those tracks where they use a lot of breaking. The heat involved can be intense and most metals can be warped easily by uneven applications of heat. The fabrication on exhaust headers tubes the process of welding causes the tubes to bend (which is why X pipes sometimes need a little persuasion to mount up the the exhaust manifold ) even when held in a fixed jig the uneven heat cooling is virtually unavoidable. Metal is far less solid than most people think. I had a front brake pad delaminate and the steel backing plate in just a few laps at the track went from being a flat 4 by 3 inch 1/4 thick to an L shaped 4 x 5 of 1/8 thickness or so as it extruded under the heat and pressure of braking !

mpesik

[QUOTE=FBIII]If I'm not mistaken the early m6 and m5 BMW's had major rotor warping issues.

FBIII- Funny you mention that. I've owned an M3- E-30 and had the same problems, even with new rotors!

SharkSkin

No.

Yes(clean hub flange)

A straightedge can tell you if the rotor has gone "cone-shaped". To check for warpage you will need a dial indicator. A good setup to use for this would be a magnetic base that you can anchor to a fixed(non-floating) part of the caliper, then put the indicator on the braking surface of the rotor & slowly turn it. If a new rotor gives you an out-of-spec measurement here, it's probably not the rotor. You probably need to clean the hub flange surface that mates with the rotor in this case.

69gaugeman

As a supplier of gauging machines to the automotive industry I deal with the like of Bosch and TRW and the like. We supply machines to check out the dynamic properties of rotors. The pulsing of your pedal is a result of what is known as thickness variation (TV). That is how thick the brake plate thickness is as you measure it all the way around. The lateral runout (within reason) (which is what you would see if you put a dial indicator on the rotor and spun it around) is accounted for by the fact that the calipers float. What happens is that the natural lateral runout if excessive will contact the pad at the high point. This high point gets worn off and now the thickness at that point is smaller than the thickness around the rest of the rotor. This causes your pulsing pedal. So in fact using your brakes gently will have a tendancy to cause pulsing sooner. If you had a 1999 - 2002 jeep grand cherokee the brakes were made by continental teves and had a seal problem that did not cause the piston to pull back enough and caused this pulsing to happen in less than 20,000km. DCX changed to Bosch brakes as there was high warrentee cost involved. Having that knowledge I had the rotors and pads changed under warrentee 3 times in 3 years with 36,000km.

Point of this => use your Porsche as it was intended to be used. Big brakes for fast stops....eh!

Rod

Captain Tal

I recently had GT3 brakes with a custom aluminum hat installed. Very nice package but I soon experienced serious vibration under hard braking. I had the rotors turned and removed about 10/1000 from the surface of the rotor and the vibration disappeared.

I think this was the result of an improper bed-in process by the installer. The pad material was bedded in inconsistently across the face of the rotor and resulted in vibration.

fabric

Not the first time I've heard this. How do I convince my wife.

Daniel Dudley

Two other problems are partially rusted rotors and mismatched rotors. Don't Know what causes mismatch, but one rotor will always lock up first. turning will often but not always help this. Letting cars sit out without being driven can cause rust to form everywhere except under the pads. You can drve off the rust, but often those areas on the rotors become case hardened. this would no doubt contribute to uneven deposits. It is never a bad idea to drive a mile or so after heavy brake use. The so called cool down, not unlike first generation turbos.

Brent 89-GT

I think he is simply overstepping with that generalization. Not to knock the guy but "THE" authority? Stoptech is a relative newcomer to the high performance braking world, not that it makes him better or worse than Brembo, Alcon, Willwood but the authority? not in my book. There are just way to many applications to make a statement like that and have it be credible IMO. I have had both, pad material adhering to the rotors and I have warped some, actually seeing them on a lathe with a dial indicator. I don't want to go as far out on a limb as the Stoptech guy but frankly I think he is just plain wrong stating anything beyond the existence of pad material adherance as an alternative to the generalization of warping. To state that one or the other is the major cause of vibes is a shaky generalization.

FBIII

Well said Brent.

ew928

The old wives tale/internet lore I heard years ago was to drive
green pad/rotors gently for 50-100 miles. Then go out for a real
hard run with some good hard braking stops.
Is this a way to deposit pad material on the rotors evenly?

I'd liked to use my S4 brakes hard but hate the idea of pulling out
clumps of Hondas/GM/Fords/Nismo etc. from the rear bumper cover.

Ernest (NYC)