Result of switching to R-compounds

uwaeve · #1 08-21-2006, 12:51 AM

Enjoy. This happened on Saturday with the White Mountain chapter at NHIS. Car and driver are fine. Steward said he was fine with it, since it really wasn't my fault. I'm pretty happy with how it went, since I kept pumping and the pedal kept sinking. I even tried to turn since the tires weren't locked. Got me a little more road, but still drove off at 45 or so. Got my hand out to wave to the corner workers to let them know everything was fine. Got back on track, and limped to the pits, pumping the brakes pretty much constantly to get a pedal. The steward had to walk with the car for 10 feet or so because I had no pedal and was using the emergency brake to stop, and drifted right past him.

Moral of the story: if I'm sticking to R-compounds and planning to continue turning 1:23s, I will need to switch to SRF and/or flush before every day. $$$$$$. Certainly glad this didn't happen going into T3, as there are tires and Jersey barriers there instead of the rock farm that I found off of T9.

jstecher · #2 08-21-2006, 01:37 AM

Oh man those calipers just looked wrecked! I cannot believe two hundred degrees difference in them from just switching to R-Compounds. I know that Conan cooked his pretty damn bad two years back at BIR with the stock setup so I am just wondering if you arent getting enough cooling to those bad boys more so than the need to run better fluid. I think you are going to cook off even the best fluid in the market running at those temps repeatably.

What pads are you running as well? I have to imagine you are above the operating temp for most street pads if you are sitting at 536 on the caliper.

uwaeve · #3 08-21-2006, 01:57 AM

I'm running Carbotech XP10 up front, XP8 out back. Rotor temps never reach 1000 deg F, according to the paint I put on them. I'm not ready to run cooling ducts yet, so I may go to SRF for the time being. It's the R-compounds plus me getting more aggressive. They reached <410 at Tremblant on treaded R-compounds, now they're down to slicks and I was out with the big boys (RG1, right below instructors) at NHIS. There were a couple of tubeframe cars out in my run group, it was crazy.

JimLill · #4 08-21-2006, 05:01 AM

other remedies might include:

- remove backing plates
- add Takspeed or similar Ti shims

billy · #5 08-21-2006, 06:39 AM

Damn
It's really likely to be cooling at this point, no? You switched the pads and still boiled em. Where did you get the thermometer? I haven't had any braking issues (besides not using them) yet and I got the Tak shims to put in now also.

uwaeve · #6 08-21-2006, 07:53 AM

Pads weren't the problem. Pad fade is a high, hard pedal with no braking force. I boiled the fluid, which was a continuously sinking pedal.

If I go to cooling, I won't be eligible for the class I want to time trial in. An idea I'm toying with for next year...

JimLill · #7 08-21-2006, 08:12 AM

The Titanium shims keep the heat from transferring from the pads to the pistons and thus the fluid..........

Conan · #8 08-21-2006, 09:20 AM

Quote:

Originally Posted by uwaeve

I'm running Carbotech XP10 up front, XP8 out back. Rotor temps never reach 1000 deg F, according to the paint I put on them. I'm not ready to run cooling ducts yet, so I may go to SRF for the time being. It's the R-compounds plus me getting more aggressive. They reached <410 at Tremblant on treaded R-compounds, now they're down to slicks and I was out with the big boys (RG1, right below instructors) at NHIS. There were a couple of tubeframe cars out in my run group, it was crazy.

If your caliper temp didn't read above 500 deg F, then I doubt you boiled the fluid. What's the MOT on the Carbotechs?

uwaeve · #9 08-21-2006, 11:10 AM

Quote:

Originally Posted by Conan

If your caliper temp didn't read above 500 deg F, then I doubt you boiled the fluid. What's the MOT on the Carbotechs?

Based on the quoted accuracy of the temperature strips (+/- 2% of the F reading), the calipers could have been anywhere between 499.8° F and 525.5° F. The boiling point of ATE Super Blue is 536° F (dry) and 393° F (with ~3.7% moisture content).
Carbotech's quoted fade resistance for the XP10 compound is >1600° F, and the rotor paint tells me that the maximum temperature seen by the rotors is <1200° F. I don't know how much hotter the pad-rotor interface is than the rotor edges, however.

Pad fade is characterized by a high, hard pedal with reduced braking torque. The failure I had was characterized by a pedal that went to the floor a few times, was extremely soft, and felt like I was bleeding the brakes with a bleeder screw wide open.

Based on all the information I have, I'm sticking with boiling the fluid.

Quote:

Originally Posted by JimLill

The Titanium shims keep the heat from transferring from the pads to the pistons and thus the fluid.

This is why I test-fit the prototypes for Vizwiz's run of shims.

This may be a temporary solution, but I don't think shims or ducting is allowed in COM time trials SSGT class, which is where I might be headed next year. Looks like SRF and frequent flushes if I go that route.

JimLill · #10 08-21-2006, 11:44 AM

SRF will not solve all the potential problems. If things are really getting Hot-Hot... then the heat in the pistons will also cook your dust seals... so watch for that after any hot run too.