96GS#007

I'm assuming you have PDR? If yes, the ride height data will just show you dive (and approximate downforce with the right math ). Since you don't have ride height data, no biggie. What you want to look at is longitudinal Gs By looking at the negative Gs.....which is braking....you can compare the SR21s to other pads you've run. Whichever pad has the most (and most consistent) negative Gs implies that whatever pad had those measures was the best regarding braking performance (since all else was the same). If it turns out the SR21s had the best data, then what happened is you found the next weakest link. If you other pads had the best data, then that says the SR21s 1) don't perform as well as other pads and 2) they take their toll on other parts (ie rotors and calipers) which is a colossal "lose / lose"

AHP

No PDR in this car, regrettably. All I have is video and lap times via Track Addict with a 10hz external GPS receiver. While Track Addict displays longitudinal Gs in the friction circle, it doesn't show a G value like it does for lateral Gs so longitudinal is probably just estimated.

I can tell you that with the SR pads my lap times were a little over 1 second off my normal pace for the conditions on the best laps. A few days later with a cheap set of Powerstop Track Day pads I was right back at my normal pace in even hotter weather. And a few weeks after that with a fresh set of tires and another set of Track Day pads I set a PB in humid 85° that was 2.5 quicker than my best on the SR pads, and in the afternoon in 97° was running consistently 1 second quicker than my best on the SR pads.

I think they're a good option for the right setup, just not my setup.

BrunoTheMellow

perhaps you’re braking too early on the stronger pads and slowing down too much. The track day. Pads may have Been keeping you from overbraking

X25

That's exactly what I thought, too, when I read the comments. That happened to me as well before I got used to pads with high bite. You need to just feather these pads most of the time, which is an uneasy feeling at first...

AHP

Yeah, that may be some of it. Frankly I haven't done a detailed sector by sector analysis since I'm not seeking a solution to running this pad. I consider it an A/B test and the output was these pads are a mismatch for me.. I was hesitant to even get into the lap times but it's the only objective data that I had.

96GS#007

I ran the SR21 pads this past Thur. I was only out for 1 session for about 20 minutes....105* air temp and 150* asphalt takes the fun out of things but I wanted to capture some tuning data.

Quick observations....
- These pads are grabby mf'ers when you apply **and** release the brakes. Very digital
- For the 20 minutes in high heat, they held up well. No signs of fade
- Can't comment on rotor wear since it was only 1 session but having said that, I saw no indications of abnormal deposits or wear starting to occur. This and $2 will get you a cup of coffee.

I'll likely be back out in August and see how they wear over a full day and see how quickly I catch on to their application and release characteristics before I decide if I like them or not.

romandian

does it really work like that? the energy dissipated by the brake system on an average is given by the power of the engine. if you brake too much you are slower at the beginning of the next braking action. no? am i missing something?

(the temp of disc and caliper maxes out several seconds after end of braking, up to 25 sec for the caliper.)

X25

If you overslow, you'll have to run the engine longer to get back to max stable speed before the next turn starts, and it all repeats. Since you spend more time putting more energy to the system, you end up increasing the load on brakes, too.

Not every track, and not every corner would allow this, but this definitely can happen : )

romandian

im sceptical physics would agree with that, but not really sure either.

X25

Check out the carousel, T6 at this track. You're limited to around 65 MPH (depending on your car and line) going through the carousel. However, most cars hit more than 100 MPH after the turn prior, T5. You can somewhat drop your speed to 65 MPH and start T6, OR you can overbrake and drop your speed to 30-40 MPH, and then quickly get back to 65 MPH by adding speed with your engine. The second scenario will undoubtedly add more heat to the brakes, even though you're turning most of T6 and post T5 about same speeds...

I hope this helps : )

romandian

i dont have any experience in analyzing a track and i know there are different ways to attack a turn. my point, however, is that the thermal inertia of the brake components is greatly underestimated. the paint will reach max temp half a minute after you get off the pedal (as mentioned above). so in the end it averages out and the demand on the braking system is given by the output of the engine. of course you can overheat a certain component (pad surface) momentarily.

(im, btw, just thinking out aloud here.)

theamxguy

Anyone have any idea when the SR 21 will be available in the Wilwood 6620 shape?

romandian

also, looking up braking energy, the velocity term is: v1*2-v2*2 (second power). so e.g. for a deceleration from 110→60 compared to 100→30 the energy is only 7% higher.

X25

Why did you choose 110 in first, and 100 in second? 100 --> 30 is almost 43% more energy dissipated compared to 100 --> 60. In a system where thermal runaway can make or break things, it's huuuge.

Again, it depends on the track, but you can dump a lot more energy with different driving styles or by slowing a bit more than needed. The physics, as you called it, is obvious, and so are the experience we have at the track: we see that happening all the time..

Note: I'm not suggesting anything about the OP's actual situation; this was hypothetical.

romandian

110 because the car was accelerating longer (in round numbers). how do you come up with 43%? (110^2 - 60^2 / 100^2 - 30^2 = 1.07)

sorry if this is going off the track.

X25

This thread is going way off track, sorry OP.

The whole point in that example was that you cannot always go faster by next turn; acceleration is not the only thing that limits you after all. If you use 100 for both, you'll get to my number.

a_ahmed

So I finally got my C5 back.

Installed EBC 2 piece Z06 rotors and cadillac brembo calipers and SR11 front pads. I have in the rear the stock C5 calipers and rotors with powerstop z26 pads.

I only drove it in the evening and not too crazy, but for anyone wondering for streetability, no noise, descent starting torque, with a few harder stops, stops much harder, I'm excited. I think the rear will need to be upgraded however, it nose dives but someone might say its spring rate too but I have descently stiff front (coilovers) I think the fronts are braking harder which makes total sense.

Just thought I'd finally share.

romandian

do you know about the spring change in the "proportioning valve" for more rear bias?

PLapping12

Glad you are getting to try them out finally! Appreciate the feedback on street manners, while not designed for the street its always interesting to hear how they behave in that scenario.

You are correct that that set up will be heavily front brake biased and most likely just get worse as the rears heat and fade.

I ran a similar set up while we were doing some testing on our endurance car due to time frame, and I started locking the fronts up because the rear was giving up the ghost. Relying on the front to slow the car too much. That was a BMW and i think the c5 does active brake bias so may not be so prevelant.

If you start activating a lot of abs that's probably what's happening to you, just a heads-up! Hope you enjoy the SR series!

96GS#007

Just adding to this. I ran the SR21/SR11 setup this weekend at Eagles Canyon. 107* out, so it was a scorcher!

The pads are definitely "grippy" which it's going to take some time to get used to. They're nearly an on/off switch when engaging the brakes so I kept over-braking. This was also my first time running the 2.7 CW layout so that certainly influences things as well. I need to look at the PDR data and see what my braking g-forces looked like.

The pads wore very well and I'm not seeing any undo wear on my Girodisc front or rear rotors. I hope to be back out again in a few week.