mjdavis

Not to start a debate or anything, but on a (somewhat) technical forum like this, we should try to avoid talking about "warped' brake rotors. Truly warped brake rotors is such a rare phenomenon that I doubt anyone on this forum (even the racers) has ever experienced it. Raising it as a possible cause for anything doesn't really help anyone with their problem.

Pad deposits on the other hand - we've all had that.

fpb111

Really?
Out of curiosity if not 'warped' what would you call rotors that have developed 0.020" run out that can be touched up true on a brake lathe?

Imo000

Pad deposit is rare I think. I've seen and had plenty of rotors that had a pretty good runout that was easily measure with a dial indicator.

mjdavis

Nothing rare at all about pad deposits. I bet that every member of this forum has had pad deposits at some point. It's almost impossible (for me) to avoid pad deposits with something like Pagid RS19s for example. The fact is that the conditions required to truly deform a properly installed brake rotor are so extreme that I think only large jet airplanes and the Space Shuttle (RIP) encounter it with any frequency.

I'll defer to the oft-cited Carroll Smith:

"...in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development programs in history - I have never seen a warped brake disc. I have seen lots of cracked discs, discs that had turned into shallow cones at operating temperature because they were mounted rigidly to their attachment bells or top hats, a few where the friction surface had collapsed in the area between straight radial interior vanes, and an untold number of discs with pad material unevenly deposited on the friction surfaces - sometimes visible and more often not.

In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures."

Edit: I realize that resorting to a third-party "expert" is a pretty lame form of discourse, but it seemed appropriate here.

DK570

Could it be related to the fluid? Today I was looking into what brake fluid to use for a flush, and found that viscosity can be very different between DOT 4 fluids. Cars with ABS should use a thinner fluid for quicker/smoother pulsing.

Imo000

"....... This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures." What exactly is this supposed to mean?!?! Very blinker fluid kind of sentence.

Capt. Obvious

I had a similar issue on my C4S with EBC pads. I attempted re-bedding them a few times and it didn't help. Finally, I took the took time to remove the pads and rotors one afternoon and gave both the pads and a good roughing up with 400 grit sandpaper.

Problem solved, and it only took about 45 minutes.

5CHN3LL

Maybe I just have crappy luck, but I've warped a rotor on two cars over the years. One was a Ford Tempo, so I don't think it was due to the massive speed I had to bleed off.

I do not think THIS thread is a case of warped rotor - still just sounds like ABS kicking in to me.

5CHN3LL

OP: One thing to remember is that when ABS is engaged, you are not stopping in the least possible distance. If you get to the point where ABS is engaged and then back off fractionally, so you are at the threshold of ABS (or nearly locked up on a non-ABS car), your braking distance is optimized.

This is even more evident in wet/snowy/icy conditions where the distance you slide with every pulse of the ABS system is increased.

Loading the brakes progressively (instead of "slamming" them on) is a better approach if you can manage it. This allows the front suspension to load, increasing the amount of grip for the front tires. If you slam on the brakes with no front-end load, there is less initial grip, so you will immediately begin to skid (or engage ABS).

ABS is a great solution in panic stop situations - in a non-ABS car, the car would begin to skid, causing the braking to be much less effective and also resulting in total loss of directional control. ABS is a lifesaver, but like many driver aids, it isn't the optimal solution for all situations.

rwiii

Thanks for that. I have only driven the car in inclement weather a few times. It is now my daily driver so I'm sure I'll get more of a taste for it. Yes when I felt it it was a panic stop and then I recreated it a few times. I don't make a practice of hitting them hard while tooling around.