Hi All,
I realize there is already a thread on warped rotors, but this one is for people who drive this car on track. I've just returned from two days at Watkins Glen and can categorically state that ther is a significant problem with the Evo's front brakes. Prior to the Glen, I got new rotors. I had the cryo-treated, I brake-trued them, I drove stop and go for 200 miles bedding in the race-pads, and then did 20 100+ to 60 mph slows gradually increasing the brake pressure. This was the most thorough bedding process I have ever done. The rotors warped after half a day at the track and this was in the rain! I am now convinced there is a design flaw in the front brake design that is causing this. I forgot to add that my dustshields were removed and I have the brake windguides. The judder was so bad by day two that I had to sit out the last two runs for fear I would damage other components in the front suspension. The wheel shook so violently in the braking zones that my helmet would shake giving me trouble seeing at turn-in. I'm not sure what to try next, but I did notice that I had to re-torque the wheels after each session. Since this is all that holds the front rotors in place, I wonder if this could be part of the problem. I was torqueing to 85 ft. lbs. If you knew me, you would fully appreciate the gravity of a situation that would force me to sit on the sidelines at the Glen.
Cheers,

 

I had one other thought. I'm going to disconnect the ABS and see what kind of brake bias this car has. Could be that there is way too much braking up front.
Cheers,

 

Could the rain be what warped them?

 

If your going to be doing that kind of racing I would suggest endless for your brake up grade. calipers, rotors, pads, and lines. front and upgrade the back with rotors, pads and lines.

 

Usually in the rain you actually end up using the brakes more than in the dry, so it's not uncommon to see brakes get treated the absolute worst in the wet, plus and deep puddles if you're lucky enough to get such conditions on track, only add to the chance of rapid cooling and warping from often the highest temps.

In the rain you often still achieve about the same speeds in the straights, but you end up having to brake even more to slow down even more for the lowered tracation in the rain.

We're you driving a wet line or dry line in the rain? I was wondering how much the AWD would help sticking to the dry line in the wet.

Sorry to hear about the brake problems, I blew my calipers up and caught them on fire on my ZX3 a few weeks back at the Motorsport Ranch.

 

At the Glen, the wet line is almost the same as the dry line, the concrete is very grippy. You don't use the brakes any where near as hard in the rain as in the dry. The rotors were properly bedded and they do not hold up. End of story for now.
Cheers,

 

What kind of times were you running? What were your impressions of the handling, grip, and acceleeration in the rain?

 

How does the rotor surface look? I attached a picture from the StopTech web site. I have had rotors look like this and felt vibrations as bad as you describe! Do yours look like this? As explained on their web site this is caused by pad material unevenly deposited on the friction surfaces. I have also seen pad imprints on the friction surface as well, and that does cause a vibration too. I am very interested to here back from you on the condition of the friction surface.

Later,
Bob

 

I will have lateral runout data this friday. I am familiar with the Stoptech site. The rotors look like there could be some friction material issues but as I stated, the bedding in process was thorough. I didn't bother taking lap times but in the rain there was no one faster. In the dry, the car stays with a well driven C5 and pulls away from an equally well driven E46 M3.
Cheers,

 

just being the devils advocate here-

you did run the car slowly after your on track sessions to let the brakes slowly cool down right? didnt just come off the track and park the car immediately after running it?

 

Brakes were cooled in the paddock. Like you, I know all the standard ways to avoid this problem but the rotors are not cooperating. If I haven't cooked the front hubs from the judder, I will true the rotors and try a less aggressive organic pad up front.
Cheers,

 

FWIW, I used to warp the rotors on my DSM with almost every trip to the track. The judder you described is very familiar to me. The car was shaking so badly one time that I drove home (and for the next couple days) using only the handbrake until new rotors arrived.

Eventually I realized my particular problem was due to my lack of attention while torquing the lugnuts. I'm not saying that's the issue here, but in my case that was definitely the problem. This was back when I was first getting into DSMs and I knew even less than I do now. I used to just grab the torque wrench, set it to 85 ft-lbs and go at it. Well, let me back up. I used to just hit the lug nuts with an impact wrench set to full high and call it close enough. Well, actually, let me go back even further. When I *first* started, I used to just grab the 1/2 rachet and 22mm socket and tighten "real good".

As you can see, I had no idea what I was doing and the results were horribly warped rotors with every trip to the track. My current technique may be a bit of overkill, but after learning my lesson so painfully, I feel justified. And I've not warped a rotor since, so I can't be that far off.

I now "sneak up" on the final lugnut torque setting. I start out with a "firm" twist on all the nuts that holds the wheel in place. Then I get out the torque wrench and set it to 45 ft-lbs. I torque all of them to that setting, then go around and check that they're all still at that setting. If some of them were already at that setting or beyond (i.e., requiring no turns to reach 45 ft-lbs), I loosen them all up and start over. I then go to 65 ft-lbs and repeat the two cycle process. I then go to 85 and repeat again. Yeah, that's like 30-40 torques per wheel, but damn it, I ain't warping another rotor just because I was feeling lazy while putting the wheel on.

I only mention this because you had mentioned having to re-torque your wheels periodically during the event. I'm not suggesting you did anything wrong, but if they were loose for whatever reason, then that may have well contributed to your problem. In my case, inconsistent torque on my lugnuts were definitely a contributing factor in my warped rotors.

Thomas Dorris

 

The only thing I can add to that is to initially torque the wheel off the ground, and then check it again on the ground. I can only imagine that the loosening of my lugnuts after a session is heat or judder related. What a tragic flaw in an otherwise super platform.
Cheers,

 

wtz,

sorry to hear about your brakes. you did not mention what kind of rotors you are using. i used to have this same problem also but have since changed to endless rotors with top secret pads and they held out after more than 10 trips to the track.

you might also want to check your suspension. if you only get the judder under heavy breaking (i.e. when the nose dives) something could be wrong there. this is not likely but does not hurt to check.

 

What pads were you running? It has been my personal experience that rotors do NOT warp, but the shudder feeling is actually pad material transfering unevenly onto the rotor. This is mainly due to poor quality pads, or overheating brake pads.

The amount of strees required to phisycally warp a rotr would instead crack it. Cast iron is brittle.

Read this: http://ww.stoptech.com/whitepapers/w...otors_myth.htm