Brake rotors warped - anyone else?

[DZeckhausen]

Originally Posted by obiwan

After a hard stop, if you sit still with your foot on the brake, it bakes the heat into the rotors which will induce the warpage. Kick it into neutral and take your foot off the pedel.

Leaving your foot pressed down hard on the brake pedal following a long, hard stop may cause a judder problem, but not because of rotor "warpage." What really happens is that you bake a pad "imprint" on your rotor. If the rotor is hot enough, like when you come in to the pit after a few fast laps, you can actually bond the pad material to the rotor and delaminate the pads.

High speed driving (race) instructors always tell their students to take a cool-down lap before coming into the pits, then put the car in neutral or park and stay off the brake pedal until the rotors cool off.

The baked on pad imprint can act like the grain of sand in an oyster. Over time, additional pad material will build up on this spot until you start to feel vibration under braking, due to the thickness variation.

Bottom line: the advice is good. But the underlying physics is different than what was described.

[Northern Rider]

Dave, I followed your bedding process on Friday. I wasn't experiencing any real problems on my 300C other than the pedal feel was softer than I prefer.

It really works! Pedal feel is much better.

The real proof came on the weekend. A buddy of mine just bought a 2003 Porsche 911 cabriolet C4. We were detailing it on Saturday when I suggested he get to a track and do driver's school. I said I'd go as well to brush up.

Well, the next thing I know, 3 of us pile into my 300C (the Porsche was too small to hold us all) and we head up from Ottawa to LeCircuit at Mount Tremblant. The Rolex endurance series was already running and we wanted to see some of it. The drive normally takes 2 hours and the road up into the mountains is rough in places and has lots of tight twisties - more than a few, off camber.

The first section was freeway with the lazer lads out collect tax money. My buddy was complaining he should have taken the 911 - we're gonna miss the race - yada yada...

Off the freeway - on to the twisties - esp turned off - time to test the bedded in ceramic pads. As you know Dave, it's all about exit speed.

Hard into the corners; brake late - small drift to overcome understeer; power on coming out. What a blast!

We picked up a 5 series bimmer who climbed up our tail coming out of a village. then we hit the real tight twisties and whoop-de-doos. The last image I had of the bimmer in my rear view was him over the centreline frantically sawing his steering wheel - out of control.

My brakes were awesome. Hardly any fade, good modulation - I could predict the rate - and they never let me down.

We made the track in 1 hour and 33 minutes. the 300C really does need a grab handle for the front passenger. Got to watch those awesome Daytona Prototypes and the GT3 guys bang it out.

Thanks for the tip, Dave. You rock!



(LEGAL DISCLAIMER: THE ABOVE NARRATIVE IS PURELY FICTIONAL.NR DOES NOT CONDONE ROAD RACING; DRIVING OVER THE LEGAL LIMIT; OR ANY OTHER POLITICALLY INCORRECT BEHAVIOR. NR RECOMMENDS THAT SENSIBLE PEOPLE WILL DRIVE A PRIUS OR TAKE PUBLIC TRANSPORTATION. OR BETTER YET, SURROUND YOUR BODY WITH BUBBLE WRAP, GET IN BED AND PULL THE COVERS OVER YOUR HEAD)

[HEMEEE]

Originally Posted by Northern Rider

(LEGAL DISCLAIMER: THE ABOVE NARRATIVE IS PURELY FICTIONAL.NR DOES NOT CONDONE ROAD RACING; DRIVING OVER THE LEGAL LIMIT; OR ANY OTHER POLITICALLY INCORRECT BEHAVIOR. NR RECOMMENDS THAT SENSIBLE PEOPLE WILL DRIVE A PRIUS OR TAKE PUBLIC TRANSPORTATION. OR BETTER YET, SURROUND YOUR BODY WITH BUBBLE WRAP, GET IN BED AND PULL THE COVERS OVER YOUR HEAD)

Love the story... love the disclaimer MORE!!

[HaTaX]

Have the same pulsing problem... It's really bad around 65mph when I apply them even lightly... Didn't think the C had ceramic pads so I assumed warpage....

I've used "premium" pads in the past to eliminate these problems before and am guessing that a nice bed in session will fix my problem... Time to find a nice quiet road to do some beating on.

I'll try it out and let you know what happens...

[albow]

I am having the feel of rotors needing turned as well at only 15,000 and less than 5 hard stops. I have never experienced rotors wearing out faster than pads, so I was really disappointed and afrid I was going to have to spend money or fight with the dealer on this. I will definitely try the bedding test when I get a chance. Thanks to Zeck for the info.

[LWOOD]

Well as a follow-up, I was able to somewhat reduce the shuddering upon light braking at lower speeds but by 25,000 miles it had gotten worse and became excessive. i took the car to an independant mechanic who works on some of my other vehicles. He put the rotors on a mirometer and some other too that measures run out and determined both fronts were warped. I ended up having them resurfaced because he couldn't get a set of new ones. We did do for a high performance aftermarket ceramic pad. My brakes are great 6 thousand later. The pulse was aking me miserable. Now it's like driving my C brand new again. The brakes, tires and alignment have set me back some change, but now the car it sorted the way I want it.
If you guys are having problems at 15-16k like I did, don't let them knock you around...make the dealer do it free.