Bill Verburg

Running rotors hot, kills rotors, pads and tires

here's a set of Pagid blacks off a 964 Cup at Watkins Glen, you see the same heat distress as on yours. As I said when I do temps I've noticed PFCs tend to be at the high end of the range seen, 993 big reds and 996/7 Cups at the lower end, street 986/7, 006/7 at the high end, particularly in front

himself

FWIW, this was my old car, and as you can see from the pic above, temperatures do not appear to be high. I believe that cooling was more than adequate, and included brake ducts, internal air scoops, solid rotors, etc).

[edit] Also, as you can see above, the REARS are also chunking. The pads in the pics are the worst examples, but virtually all of the yellows I have used chunked to some degree, mostly on the trailing edge.

-td

Steve Weiner-Rennsport Systems

JMHO, but the best way to measure brake temps is by using the heat-sensitive paints on the circumference of the rotors. This gives you a MUCH better snapshot of your peak rotor temps; something thats directly related to peak pad temps.

If you have chunked all four corners, I'd say that your operating temperatures exceed the working range of the pads and you need either more efficient cooling or a larger rotor package that can dissipate the accumulated heat.

One really needs to see the results from using the paints before deciding on a "cure".

Bill Verburg

Steve is correct if you want to know absolute temps, I just do informal comparisons of my run group and friends run groups when we come off the track, it's way below the peaks but fine for comparisons. And clearly shows whats happening w/ various setups and pads, when you see 2 identical F class SCs but w/ different pads w/ equal drivers showing disparate temps some inferences can be made as to the pads effects

himself

IMO, it was the pads and not the setup. I find it difficult to believe that I was exeeding 1100 on the rotor side, but not getting any brake fade and not hitting over 350 on the caliper or boiling Motul 600. As anecdotal evidence, I have used my thermal temp gun on the rotors, and never registered over its max [968 F] - but this was always after a cool down lap. [FWIW, these are on sale at harbor freight right now for $30.]

Also, there was not much more I could do as far cooling is concerned. The car already had solid rotors, bigger brake ducts [GT3], and "forced" air ducted from the front of the car directly to the front rotors.

But then again, what do I know.

-td

Steve Weiner-Rennsport Systems

With all due respect, you'll never know your peak rotor temps without using that special paint kit.

Infared guns cannot show peak temps after you've driven into a pit or paddock to take the measurements,... While those are useful tools, they are not accurate for showing peak brake rotor temps and thats critical information.

Dwane

Are you worried, i am going to out brake you, when I get to run in your group?
Putting the pads on for the last event?
Is Nat going down with you in August?
later
Dwane

himself

Agreed on the temps, which is why I said anecdotal evidence. I have no doubt that you need special tools to get accurate readings. But I don't think you don't need perfect data for this scenario. That is, I still don't get how a 996 street car is somehow getting Pagid Yellow temps over 1100 (so that they chunk front and rear) - without encountering any other symptoms at the same time, i.e., no brake fade and no boiling fluid. Personally, I still think it was the pads. Maybe I got a bad batch, or they got wet, or they needed better bedding, or something else. But it was definitely not temperature. But we will never know, since the car is long gone.

FWIW, I checked my GT3 Pagid pads last night, and they also have chunks missing. IMO, GT3s have plenty of brake cooling - and I am also running solid rotors...

-td

AllanJ

Are you running the 996 Cup brake ducts or the regular GT3 ducts? Cup ducts are much better.

...and what rotors specifically are you using? "Solid" rotors to me means no internal vanes which is very doubtful in your case. You'd want them to be slotted too.

Cheers,

himself

Meh. I was using "solid" in direct contradistinction to cross drilled rotors. This terminology is probably incorrect, but with the clarification, I think most will get it. And "slotted" (to me) means slots on the face of the rotors, which is different from internal vents or vanes. In any event, I am running properly vented and slotted rotors by Deman. These are not cross drilled.

FWIW, cup ducts are nothing more than really expensive shovels and ground scrapers

-td

DWS964

OK I am going to jump into this discussion with my own request for "read my pads". I recently installed Pagid Oranges in my 93 964 C4 for DE's. First time at Road America, and then on Putnam Park, and back at RA. The pics below show the pads after the last visit to RA - the first pic of the fronts showing chunking and a lot of wear. These had been used in only 8 DE sessions at Putnam Park and 8 sessions at RA, since new. The second pic of rears shows less chunking, but still not "pretty". These had been used on the front at RA for 8 sessions, and Putnam rear 8 sessions, and rear at RA 8 sessions.
First, I know I have a lot to learn, and am probably using the brakes too much - not enough finesse. Even though the evidence might be that the pads/rotors were running hot, I had zero problems with boiling the fluid - I am running fresh Motul600.
I put the pads in before the 6 hr drive from IN to Road America for the Nord Stern DE. I noted a large amount of dust after the "commute" to RA. I "assumed" that the bedding-in would be completed during the first session on the track. I also noted a developing pulsing in the rear brakes after a few track sessions - and I assume this was from uneven deposits. I also drove with the pads all week while at the KIC, and then for the drive home.
We drove in some very heavy rain during the week. The comments about keeping them dry makes me wonder.
Ideas on why I had such high wear rates, and "chunking"? My rotors do not show much additional wear.
I recall reading that prior to bedding in, the pads may operate by "abrasion" until the material is transferred to the rotor surface and then the pads operate by "adhesion". Is this why my pad wear rate was high?
Or is it due to using Oranges, when Craig and others were trying to convince me to use the "economy" of Pagid Yellows?
Thanks for all the help, as always.

Turbodan

I am no expert. I used the orange on my 993 and loved them they lasted a long time. You must be smooth on these and either fully on or fully off of the brake with these pads. It looks like you may have not done this. but they don't look that bad just a lot of wear over 8 sessions.

Steve Weiner-Rennsport Systems

Brake pads "chunk" when the binder that holds the material all together fails under excessive heat and that same level of heat accelerates pad & rotor wear.

There are many reasons this can happen that include:

1) Wrong choice of pads.

2) Insufficient cooling.

3) Braking technique.

4) Insufficient rotor mass to dissipate the accumulated heat. This is exacerbated with additional grip of DOT-R type tires that puts a LOT more thermal stresses on the brake system. Using larger rotors (with matching calipers) reduces operating temps.

When the front brakes show heat stress while the rears look good, indicates too much front brake bias and that can be aleviated in several ways. One easy way is by using different pad compounds on the rear.

Your brake "engineer" is supposed to help you choose the appropriate pad for ones' application, taking into consideration your tires, vehicle weight, power, track configuration, what kind of cooling you have (if any), rotor and caliper setup, and driver skill levels. Its oftentimes not a "one-size-fits-all solution.

In some cases, measuring peak rotor temps helps one make the correct choice of pads and this is especially important, given the cost of these things,....

sig_a

In some cases, pad compound or manufacturer defect isn't always the cause of premature wear or disbondment. One cause could be incorrectly aligned pistons after caliper rebuild of older ATE's with twin pistons. Not sure that's the case with any models beyond real 911's.

I have had good luck with Pagid orange front and rear. Also black front and orange rear with a great deal more initial bite. Light weight 15 inch wheels with DOT slicks also add to brake component life.

Bob Rouleau

On my 996 GT3 I went through front rotors rather quickly until I went to cup brake ducts and RS 19 fronts with RS 14 (black rears. As Steve suggests above, the Black pads in the rear improved brake bias and made the rear rotors do more of the work. With 50 odd track days per season, I was able to do a full season on two sets of pads and one set of front rotors. Previously I would go through front rotors in about 12 days!
The rotors needed replacement because of cracks which exceeded the spec.