dsb2695

I asked this question a few years ago and the reponses seemed as though this was unique to mine, but I thought I'd try again.

I am running stock rotors, Hawk HP Plus pads, stainless lines and Motul fluid.

I run very agressively (is there anyother way). I never have had an issue with pedal fade but have issues with brake fade on the rears. It seems to be only the rears. Last year at the Dragon after a run down US28 from Fontana Village to Deals Gap I actually had the rears smoking.

From years of auto crossing and track events I know this doesn't hurt the pads. They are made for this kind of punishment.


I've had-on other not so hard runs-this same problem of over heating the rears.

Just wondering again, if anyone else has this problem. I have wondered if I may have a bad porportiong valve which is allowing too much bais to the rear. I know this car has understear issues and so I am replacing the rear sway bar to a stiffer bar, it seems this car is hard to use the brakes to set the car into a corner.

rob.ok

What happens when you engage ABS? How did you burnish the pads and rotors? Were the rotors new?

I seriously doubt that there is a bias problem. If you have too much rear bias, then it would be very easy to detect. When the brakes are at operating temp (not over....which should be your first 2 hot laps) the rears will engage ABS before the fronts and under threshold breaking the rear will wiggle quite a bit and possibly upset the car. If your trail braking with too much rear bias, the rears will lock up or at least slip more and allow the car to rotate better (if its too much your gonna rotate right into a spin). Too much rear bias under trail braking will not cause the car to understeer, in fact it's an effective way to get the car to rotate.

Generally track guys will use a less aggressive rear pad. Using the same pad front and rear on the s2k can create a situation where the rears have more bias simply from the initial bite and torque curve of the pad compound. This can make it difficult to drive like I mentioned. However, there are some that prefer more bite in the rear to help rotate the car. If your running a very aggressive rear pad in comparison to the initial bite and ramp of the front pads. They can get very hot, but generally will not start to fade until the fronts give out and shifts even more of the braking forces to the rear. At which time they will most likely fade as well. I think its pretty rare for us to fade the rear pads first in any given situation.


IMO HP+ is not the best pad out there. They don't get up to temp quick enough for autocross and they fade badly within 2 laps on track (which is still more abuse than anyone could throw at them on the streets). For track events I would suggest you start out with CarboTech XP10 & XP8. For street use just stick with the OEM pads and slow it down.

This is what HP+ looks like after only four session on track with street tires. The chalky white residue is a mystery to me.



-Rob

dsb2695

Thanks Rob for the info.

I have had a few guys make the same suggestion about a less agressive pad on the rear.

As for trail braking I'll use this method on a track to help with the understear but not on the street. It's tricky to learn and control so I don't risk it on street driving.

When I put the Hawk pads on I used the factory rotors but did have them turned so they were clean. Unfortunately, doing this at home and not at a track make it a little difficult to bed-in. You try your best to follow the proper proceedure but even getting out of the city into open roads can be a challenge.

As for what happens when the ABS engages, it seems the fronts are engaging before the rears. I know this doesn't make sense as factory's always setup the other way. Just as they design cars to have some understear. Easier for the average driver to correct!

CarboTech seems to be what many others are recommending now. I think I may give them a try. My only concern with the stock rears is, and I've had this happen, is the compond used to mate the pad to the plate can't stand much more than everday driving heat and if subjected to repeated hot laps will separate.

On a side note, I noticed from your pictures on various tracks but note the roll cage is still to come. Does Buttonwillow etc, still allow this?

rob.ok

I've run the Carbotech pads and can testify that they are true race pads and they will not crumble. You should not daily drive on them as it's simply a waste of money. Daily driving on race pads will eat up the rotor and wear out the pads about 3-5 times faster than a normal set of street pads. It's best to have two sets of rotors and pads; one for track use and one for street. In the end you actually save money.

I actually prefer Cobalts products but if you ave never used a serious track pad then the best place to start is Carbotech.

Most of California's tracks still allow the OEM roll hoop on track. I have a feeling that that will change soon though as street s2ks are running lap times faster than most spec racers. I did get my safety gear installed...you can see it towards the last pages in my build thread.

BTW you always want the fronts to engage ABS first. If the rears are engaging it first then there is a problem (generally with bias through use of too aggressive of a rear pad compound or suspension settings).


-Rob