[Ryephile]

After cool-down and parking in the paddock, my IR gun was showing 670F on the rotor hats and 450F all around the front caliper.

I ordered some Alcon caliper temp stickers to verify the caliper temps, but it'll be a bit until the Camaro's next track day.

[MatthewAMEL]

Those are great temps and much lower than I would have suspected.

I was 700+ in my Focus ST. I haven't used the gun on the 1LE yet.

[glamcem]

I will see if I can order some sort of thermal paint. TrackReady1LE mentioned that the DBA already has the thermal paint on it. If they don't last more than 4-5 events I will most likely install the DBAs very soon and report back

[Ryephile]

Originally Posted by MatthewAMEL

Those are great temps and much lower than I would have suspected.....

Ahh, no sorry I can't agree with that. 450F caliper after cool-down lap means it's way over that during hot laps, and that puts it squarely in the "too hot" category.

The rotor is also clearly overheating and/or is bad alloy, given the checking/crack marks.

[Th3Beast]

Originally Posted by MatthewAMEL

Those are great temps and much lower than I would have suspected.

I was 700+ in my Focus ST. I haven't used the gun on the 1LE yet.

Small world. I was seeing 700-730 on the rotor surface after two cool down laps in my '15 Focus ST. I even did DIY air guides that attached to the control arms to help. I never did get them to fade them with Hawk HP+ pads in there even at those temp. The factory caliper paint and outer piston dust protector are another story lol.

With my 1LE, I was seeing about 640 on the rotor surface and 330-350 on the caliper with my IR gun last time out on the track a couple weeks ago. That was after a good cool down lap. One session my front brakes were still smoking when I got back to my parking spot after my cool down... had to jump back in an keep driving her around lol. I'm still running stock pads FYI. I did a good bed-in procedure the day prior and they worked great on track.

[glamcem]

I don't have the temp indicator paint but notice the white 1LE letters? They're not white anymore more like yellow, the caliper paint is also a bit different now (orange-ish) compared to rears

[MatthewAMEL]

Originally Posted by Ryephile

Ahh, no sorry I can't agree with that. 450F caliper after cool-down lap means it's way over that during hot laps, and that puts it squarely in the "too hot" category.

The rotor is also clearly overheating and/or is bad alloy, given the checking/crack marks.

I'm just learning all this stuff, but I was getting 700F+ on the rotor after cool down. I just realized you mentioned caliper.

Is it better to measure the caliper temp than the rotor temp? I was using rotor to get an idea of what temps the pads were seeing.

Caliper give you fluid temp?

Thanks.

[Ryephile]

Originally Posted by MatthewAMEL

I'm just learning all this stuff, but I was getting 700F+ on the rotor after cool down. I just realized you mentioned caliper.

Is it better to measure the caliper temp than the rotor temp? I was using rotor to get an idea of what temps the pads were seeing.

Caliper give you fluid temp?

Thanks.

No worries. The thing about rotor temps is an IR gun usually won't pick up an accurate temp because of the reflectivity of the rotor. You really need to do temp paint on the rotor. With an IR gun, the closest you can get to accurate temps is the rotor hub (on a 2-piece), and the caliper, maybe the pads if the IR gun can get line of sight. Maybe best case is if you have a bunch of transfer layer on the rotors that make them less reflective.

In any case, the resultant condition of the rotors and pads will generally indicate how hot they get. The reason for the checking/cracking is the very high temperature swing above ambient. The iron grows so much that when it cools the shrinkage forms the cracks.

The fluid temp will vary depending on where it is in the line. At the reservoir I IR'd 120F, but it'll be closer to the caliper body temp inside the caliper. This is why it's so important to run a good brake fluid with a high wet boil temp.

[Th3Beast]

Originally Posted by Ryephile

No worries. The thing about rotor temps is an IR gun usually won't pick up an accurate temp because of the reflectivity of the rotor. You really need to do temp paint on the rotor. With an IR gun, the closest you can get to accurate temps is the rotor hub (on a 2-piece), and the caliper, maybe the pads if the IR gun can get line of sight. Maybe best case is if you have a bunch of transfer layer on the rotors that make them less reflective.

In any case, the resultant condition of the rotors and pads will generally indicate how hot they get. The reason for the checking/cracking is the very high temperature swing above ambient. The iron grows so much that when it cools the shrinkage forms the cracks.

The fluid temp will vary depending on where it is in the line. At the reservoir I IR'd 120F, but it'll be closer to the caliper body temp inside the caliper. This is why it's so important to run a good brake fluid with a high wet boil temp.

Great info! Do you think bringing the rotors up to temperature a little more gradual would help things? Maybe taking an additional warmup lap?

[TrackClub]

Here's a good link that de-mystifies the brake temps as commented by the pros from Wilwood and Pagid. Note the comments on street vs race pad operating temps, how best to measure them and importance of choosing a right pad.
http://cartechstuff.blogspot.ca/2016...tures.html?m=1


To me brakes are like tires: you can gain pace by running slick but they may cord in 2 days. With brakes you can use an aggressive race pad but it will wear out fast and eat your rotors faster. It is always a compromise.

OTOH it seems stock brakes are pretty good and Provoste even uses them with slicks. So no reason to be overly concerned it seems albeit the above advice to use a good fluid is obviously a must.
Beyond that, one can experiment with perhaps a better pad, or a disk, or both. Just don't expect miracles with 3747lb car

Brake temps (and all the other temps) will depend on one's driving level, style, track, ambient, humidity, traffic vs clean air, etc.
All discs/rotors will develop heat check micro cracks. The key is to monitor them and once they get too wide or start running towards the edge then it is time for a new set of rotors lest it could split.

It is important to cool thing down properly, especially if one doesn't get a full lap to do so. Regardless and as a rule of thumb I've been using oil temp as an indicator. If after my cool down lap oil is above about 212F then I'd go for a ride in an empty paddock or access lane etc until the temp dipped below it. Then park in my spot trying to coast in and use as little brakes as possible. NEVER use a parking brake as it will warp R Rotors. Then after 10mins or so, I'd roll the car half a tire length to reposition calipers to the opposite side of the rotor (use a wheel stop). That's about it.

Always inspect your pads, rotors, tires and wheels after each stint plus hot tire pressures. Re-torque your wheels after they cool down. Check oil. You're done. HAVE FUN!

[Ryephile]

Originally Posted by Th3Beast

Great info! Do you think bringing the rotors up to temperature a little more gradual would help things? Maybe taking an additional warmup lap?

Glad to help.

No, it's the peak temp that causes the rotor cracking. With better ducting, the temp would be lower and the thermal expansion would be less.

Incidentally, when I had my car up on jackstands yesterday, the inboard rotor faces have much less graining/spidering than the outboard faces. Based on that the brake ducts are getting more air to the inboard of the rotor and the outside is relatively hotter. This makes me wonder if we'd see the same asymmetry with the dba rotors with their different vane design.

[TrackClub]

Originally Posted by MatthewAMEL

Those are great temps and much lower than I would have suspected.

I was 700+ in my Focus ST. I haven't used the gun on the 1LE yet.

I'd agree especially given the weight of the car and a hot shoe driver

[glamcem]

I have 3 other events on my calendar this month (12th at the Ridge, 20th at the ORP and 24th at the Ridge again) so will be reporting about the rotors.

I wonder if using low tq pads was the cause of the rotor wear in Ryephile's case but he did mention his looked similar after the second event. I could only do one full event and two half events so far meaning it may be too early to come to a conclusion.

Another good read from the Corvette forums that X25 shared with me (link : https://www.corvetteforum.com/forums...post1589999617

Bite.
The majority of people think a high bite is good. Again Brakes are not the same as horse power, More is NOT better. We are trying to build a balanced system, not a monster. I’ve heard the Wilwood rep at events talk about “huge bite”. I have beef with wildwood FYI. Another time for that story. High bite does have its place but road racing is not it, allow me to explain. Bite will be reflected as a spike on a dyno graph. It’s the characteristic of the pad when it first comes in contact with a rotor. The pad compound and rotor slot profile will affect the pads Bite. Generally manufactures have their own bite characteristics. So a hawk dtc-60 will have a similar bite as a dtc-70, same goes for PFC and for Padgid. When picking out pads you want to find a pad with soft bite. “Why?” you might ask, and I will tell you. This initial application of the brakes is the only time you can be vigorous on the pedal. If you have a pad with softer bite you can really jump on the brakes. It will help keep the tires cohesion with the track. A higher bite pad will have a greater tendency to lock up a tire and flat spot it, flat spots cost money. The pads that have soft bite are the higher priced pads the pro’s use. Brands like PFC, Padgid, and Project Mu. Brands that have a very high initial bite I recommend for drifters. These are the people that want to very easily lock up a system. Brands for them are wildwood and hawk.


Mu, Torque, coefficient of friction.- all the same thing.
Tq of the pad happens during the deceleration process. This is the time while the brake is applied. Tq is the pads bread and butter. This is where people like to get themselves in trouble. Remember this isn’t horsepower, more is not better, and less won’t make the car easier to drive. When I give classes I start out with a question, I ask “what stops the car”. 90% of the time People shout out “the brakes”, I say “WRONG!! the tires stop the car”. It’s a cheap move, but it quickly gets my point across. For picking out a pad we want to match the TQ/Mu levels to the tire being used. The big mistakes I see are, using too much TQ FOR THE TIRE, too little TQ FOR THE TIRE (see a trend?), not balance the system. The PFC 05 compound is a ultra-high torque race pad. Example: on a corvette with the 05 compound matched with a set of BFG rivals or Hankook RS3 they would smoke the tires regularly. That car would also lose all Modulation (covered later). The pedal would turn into a light switch (off/on). This is the main reason Mu numbers are not published. Brake manufactures don’t want you running out buying the top shelf, and having a chassis that can’t take it. For those pads I would want to see a good amount of downforce, a big +285mm slick tire before I could recommend them. On the opposite side of the coin too little tq. I see this a lot with track noobs, and people that are a bit timid. The noobs sometimes just don’t know any better and just run street pads. The people that are timid think that a lower tq pad is better for someone who is learning. Low Tq pads that get overpowered by the tire can very quickly melt an entire braking system. Low Tq pads have a tendency to leach heat into braking components. A lot of time when I have customers that are boiling their fluid, they will have a pad that has too low of tq. Again we need to match the pad to the chassis. Generally padgid yellows and PFC 01 is a good combination for a normal track driven corvette.
The final issue I see is balance. The single most important thing you can to increase braking performance is to balance your system. An example story. I had ordered a bbk for my car. All big brake kits come with crap $2 pads. unknowing I took those pads to a track day and proceeded to smoke the hell out of them. I had an autocross the next weekend so I ordered up a set of HP+ for the front only. Took them out and beaded them on the street, everything felt fine. A reminder that I had cooked Chinese pads in the rear of the car. I line up at the autocross for the start, I charge down a good size straightaway, I reach for the brakes and got nothing but smoke. I locked the front tires and proceeded to fly off the track and into a berm. What happed is I increased the Tq of my front brakes somewhere in the 100% range, but the rears where completely lacking. I increased the TQ but decreased the overall performance of my chassis. When buying race pads don’t forget about the rears, they are 50% of your system.

Modulation
You will feel modulation when you lift off the pedal, it’s the release characteristic. This characteristic is the most noticeable. It’s also the most dependent on the chassis! Another short story. In 2010 I was racing in the 24hours of lemons. We had a ford escort with 205 (tiny) falken 615k. the owner called up Porterfield and just ordered the most expensive pads they had for that car. Going into turn 1 the brakes where strong, very strong but all the time I made in brakes, I lost when I couldn’t keep up the momentum. Entering the turn the modulation was a light switch it went from 100% on to 100% OFF. Forget about trail braking, that would be impossible. What effects modulation? The pads will have their own characteristic, generally an over tq pad will kill modulation. So it’s very important to have the correct compound.

[TrackClub]

Yep another great read. It is all about balance. Thx for posting it Cem.