Track brake tech primer

[DPE]

Swoope, what are YOU doing here? Good to see you though, regardless . Been awhile since my RX8 Club vendor days. Have you come over to the dark and dangerous side of American muscle cars too? Looks like an RX-8 track car in your sig. Probably what I should have done as I doubt there's a better car for track use out of the box for under $40k, but I just couldn't resist the V8 sounds and power even with a now-second-rate 4.6L.

Dave, 25-30 track events is 3 seasons for me in good times so my consumption rate on tires/brakes/hubs should be more than a bit less than yours . That, and I haven't a clue as to what I'm doing as far as driving a Mustang properly on track, so it'll take a little time to build back up to a decent pace I suspect. Or maybe just a couple events, but you know what I mean. Thanks for the tip on keeping understeer at bay to save front tires. I usually brake pretty hard and late and then trailbrake to point the nose at the apex (if I haven't already missed the apex), being used to FWD and AWD cars that don't necessarily like to turn (excluding the RX-8, which loved to turn). Probably have to be a little more careful not to overcook, but I can do that. From what I can tell being semi-sane on the street, the car is kinda numb (all stock) but seems to do what I ask it to do and is even relatively balanced compared to what I was expecting.

Sadly I'll have no camber adjustment for a little while, having just bought some GT500 wheels with tires and race pads from Carbotech and, well, the entire car in the past month, but once the money tree starts blooming again I'll do Konis and Steeda Sports along with at least Steeda upper mounts to get some more negative camber up front. Reminds me I still need to figure out ducting too; just no inexpensive, nicely integrated solution for the 2010s yet. I'll figure something out though, even if it has to be a touch ghetto in the near term.

Phil
2010 GT

 

[Swoope]

Swoope, what are YOU doing here? Good to see you though, regardless . Been awhile since my RX8 Club vendor days. Have you come over to the dark and dangerous side of American muscle cars too? Looks like an RX-8 track car in your sig. Probably what I should have done as I doubt there's a better car for track use out of the box for under $40k, but I just couldn't resist the V8 sounds and power even with a now-second-rate 4.6L.



Phil
2010 GT

doing research. did the same before the rx8. did 6 months before i got the 8.. guessing going to do 9 months here..

deciding between boss and gt. god i am going to miss 17 inch wheels! note my first car was a 66 mustang k model coupe. yep i wish i still had it.

if someone got the forced induction right in the rx8, doubt i would leave. or the mustang would be just a daily driver.

nice to see you hear.. so much more info and options with the mustang! lol

btw, dave great write! lots of great info, and very correct..


beers

 

[95CobraR]

Nice write-up, Dave.

.....and of course, brake ducting. Quantum Motorsports, Steeda, and Agent47 all sell ducting kits, and all of them work fairly well. If you're leaning towards the more hard-core end of the spectrum, though, you may want to roll your own. It'll save you some money, and give you more efficiency in cooling. Butler-Bilt inlets, QMS high-temp duct hose, and fabricated backing plates will let you get more airflow through the rotor, but too much of a good thing can be bad! At the really high-speed tracks, I have to tape off part of my inlets, since I can over-cool the brakes and actually drop the temps below the point where the initial bite is still good.

I've never experienced brakes that got "too cool" due to brake cooling ducts.

I would suggest that this is just as important as good pads, rotors, and brake fluid.

I've found that the ducts work well when aimed directly at the caliper (not on the rotor). It requires the largest diameter inlet and hose that you can fit. I've also found that the hose should be firmly located about 1" away for the caliper to allow the flow to escape while still pouring fresh air on the caliper.

Potential for pad knock-back. This occurs when there is play in the wheel bearing or major runout in the rotor, which causes the pads to be pushed away from the rotor surface.

Pad "knock back" can also incur when you use the curbs to help turn the car. The violent action of hitting the curb can push the pad back.

Most guys brake way too early before a corner. I believe in the "Hippopotamus Rule".

Once you are comfortable at a track, you should pick a corner with run-off area or a gravel trap. Then when you see your normal braking point, you should count one hippopotamus before braking. After you see how well this works, you do "one hippopotamus, two hippopotamus".

Just don't go beyond three hippopotamus.

 

[SoundGuyDave]

Nice write-up, Dave.


I've never experienced brakes that got "too cool" due to brake cooling ducts.

I've found that the ducts work well when aimed directly at the caliper (not on the rotor). It requires the largest diameter inlet and hose that you can fit. I've also found that the hose should be firmly located about 1" away for the caliper to allow the flow to escape while still pouring fresh air on the caliper.

Thanks, man! I have to tape over part of the brake duct inlets on mine at Road America, where the 145+MPH LOOONGGGGG straights drop the pad/rotor temps well under the 450* minimum temp required for my pads to really bite and start slowing the car down. For the typical "club track" of around 10-12 turns in 2 miles or so, no biggie, but going into T1 at RA hot, and hitting the pedal and feeling like there's no bite to the brakes can be a bit unnerving. After I taped up about 1/3 of the inlet surface area, there was still enough temp in them so that when I hit the pedal, the brakes bit and the car started slowing immediately. Much more consistent pedal pressure also leads to more confidence to go in deeper and harder... Directing the airflow into the hub of the rotor does a few things, first being to cool both the rotor itself (thorough the vanes) as well as the hub and bearing assemblies. If you're actually cooking the calipers themselves (as opposed to overheating the pad/rotor interface, which transfers to the caliper), then run a second duct, but you have GOT to keep the rotors cool. They're your primary heat sink for braking energy.

Pad "knock back" can also incur when you use the curbs to help turn the car. The violent action of hitting the curb can push the pad back.

A couple of things: First, you have to be fairly lightly sprung to keep the car from getting all out of shape if you're curb-hopping. That said, what I think you're experiencing is not the inertia of the pad itself pushing in the pistons, but compliance in your spindle and bearings under the impact causing the rotor to momentarily run off-center and push in the pad and the pistons. Same effect, same result, differing cause. Solution would be to LFB a touch right after the curb to reseat the pistons. Better solution would be to stay off the curbs, and figure out what needs to get tweaked to get the car to rotate...

Most guys brake way too early before a corner. I believe in the "Hippopotamus Rule".

Once you are comfortable at a track, you should pick a corner with run-off area or a gravel trap. Then when you see your normal braking point, you should count one hippopotamus before braking. After you see how well this works, you do "one hippopotamus, two hippopotamus".

Just don't go beyond three hippopotamus.

If I did that, I would start braking somewhere like 60' past the far edge of the track!! Honestly, I agree, most people DO brake far too early, and too softly. Proper braking technique is to rapidly depress, but not slam the brake pedal down until you start getting indications of lockup or ABS activation, and then start easing off the pedal to maintain that edge-of-lockup threshold as the car slows. Once that has been mastered, start monitoring the engine RPM at track exit, where you finally open the wheel completely. Move your braking point closer to the corner in increments of 25' or so, until you see a drop in engine rpm. That means that your last braking point was too far in, and you wound up blowing the corner, thus having lower exit speed. Move the braking point back out 15-20', and compare RPM again. Then move the braking point inward in 5' increments, and you'll eventually find your PERFECT braking point. Please note, however, that until you can hit your marks (brake point, turn-in point, apex, throttle pick up, and track out) with real consistency, it's not as productive as it could be. As Sam Strano put it, it's much better to go into a corner 5mph too slow, than 1mph too fast. To that I will add that my method requires neither a good runoff area or gravel, and will not actually wind up with you having an "off" at all.

Last point is that by doing the threshold braking at the absolute last possible instant, you have ZERO margin for error. All it would take would be a tiny amount of glycol down on the track, a fraction of a second's hesitation in brake application, slightly higher than normal tire or brake temps, or any sort of traffic, and you are NOT going to have fun trying to recover. No margin means having nowhere to go unless things go perfectly. How much margin you allow yourself is dependent on a lot of factors, one of them being how readily you can replace the car...

 

[pcdrj]

A couple of things: First, you have to be fairly lightly sprung to keep the car from getting all out of shape if you're curb-hopping. That said, what I think you're experiencing is not the inertia of the pad itself pushing in the pistons, but compliance in your spindle and bearings under the impact causing the rotor to momentarily run off-center and push in the pad and the pistons. Same effect, same result, differing cause. Solution would be to LFB a touch right after the curb to reseat the pistons. Better solution would be to stay off the curbs, and figure out what needs to get tweaked to get the car to rotate...

If I did that, I would start braking somewhere like 60' past the far edge of the track!! Honestly, I agree, most people DO brake far too early, and too softly. Proper braking technique is to rapidly depress, but not slam the brake pedal down until you start getting indications of lockup or ABS activation, and then start easing off the pedal to maintain that edge-of-lockup threshold as the car slows. Once that has been mastered, start monitoring the engine RPM at track exit, where you finally open the wheel completely. Move your braking point closer to the corner in increments of 25' or so, until you see a drop in engine rpm. That means that your last braking point was too far in, and you wound up blowing the corner, thus having lower exit speed. Move the braking point back out 15-20', and compare RPM again. Then move the braking point inward in 5' increments, and you'll eventually find your PERFECT braking point. Please note, however, that until you can hit your marks (brake point, turn-in point, apex, throttle pick up, and track out) with real consistency, it's not as productive as it could be. As Sam Strano put it, it's much better to go into a corner 5mph too slow, than 1mph too fast. To that I will add that my method requires neither a good runoff area or gravel, and will not actually wind up with you having an "off" at all. ...

Great stuff Dave. Taking notes here.

 

[DPE]

I tend to use brake markers rather than hippopotimi (plural?), but not all corners have markers of course so perhaps I will try that. Might use an animal like 'bird' though; much quicker to say .

In all reality, for someone in my shoes not trying to eke out the last tenth, it's probably moot. I do brake very late and typically pretty violently compared to most track day folks, and I usually make up a ton of time on people under braking. However, I'm not racing and am just out having fun, so I try to leave a bit of margin. Once I find a reference point (be it a brake marker or a pavement seam or what have you) where I can brake hard and trail brake into a corner and get a little rotation but not be on the hairy edge, I usually stick with that and focus on locating an apex. Good info though, should I develop some bravery.

Swoope, you will indeed miss 17" wheels. The good news is there are some really good 18" Brembo-clearing wheel options for the Mustang that aren't too expensive, but there is no getting around how expensive (relatively) the meaty 18" tires are. Part of the deal. And my 2 cents, get a regular GT 5.0. With the discounts they have on them you can get a Premium with Brembos and your choice of gear for a good $10k less than a Boss. And you'll have a nicer car to drive around day to day, and be able to add Boss power and Boss handling for a LOT less than the $10k difference. Plus, for a car that'll see the track, there's that chance of all going wrong with no insurance coverage and you'll want to be in the cheaper car if it does . I'm sure others may think otherwise, that's just what I think.

And last, related to the OP, Ford Racing appears to have released a brake cooling kit for around $250 that hooks up to the 2010+ CS/Boss airdam where the foglights go. So get said airdam for around $250 (you can swap it with your OEM GT airdam so no paint required) and the new brake cooling kit for the same and you have a nicely integrated solution for the 2010+ cars. Not cheap at $500, but not absurd either. I'm pretty confident the Quantum Motorsports kit would also hook up to the CS/Boss airdam, so there's a little money to be saved there. Planning on going this route as soon as the parts are available. First track day (assuming good weather) is April 1st for us up at MAM near Omaha; looking VERY forward to it....

Phil

 

[Shotokan1509]

How are the GT500 Brembo stock lines, soft & squishy needing stainless replacements or are they upgraded too?

 

[RedMosesSC]

Good read, great write up. Right on Dave.

 

[Defiance GT]

How do u guys like ebc. Im putting on the blue which is the first full track pad that has cold temp braking

Sent from my DROIDX using Tapatalk

 

[95CobraR]

I have to tape over part of the brake duct inlets on mine at Road America, where the 145+MPH LOOONGGGGG straights drop the pad/rotor temps well under the 450* minimum temp required for my pads to really bite and start slowing the car down.

I am very impressed that you use a pyrometer to gauge rotor temps. Is it a laser or probe meter (or a data system on board the car)?

I've raced RA about eight times (mostly, at the Kohler Challenge).

How do you note rotor/pad temps? Do you come in the pits and do a quick measurement? Or do you have a data system that downloads temps from the car sensors' extra computer?

Yes, there are three straights at RA:
1) The main straight goes into T-1. It's a fast turn. no problem here.
2) The Morainne Sweep into T-5 is very fast (it's downhill).
3) The rear straight is very difficult. If you go through The Carousel (T-9 and T-10) perfectly and through The Kink (T-11) wide-open, and through Kettle Bottoms, we find Canada Corner (T-12) to be a problem.

Last point is that by doing the threshold braking at the absolute last possible instant, you have ZERO margin for error...

That is true. Yet, at RA in those three turns, there is a big gravel trap at the end. RA has a roll-back at these turns. They'll pull you out without losing a lap.

I would never recommend hippopotamus braking in The Boot at Watkins Glen. There is just one good gravel trap there. The rest is pure guard rails. One mistake there, and you car is slapping some major hard armco.

 

[SoundGuyDave]

I am very impressed that you use a pyrometer to gauge rotor temps. Is it a laser or probe meter (or a data system on board the car)?

Neither, actually, just experience, experimentation, and consultation with my friendly neighborhood Hawk rep. Jay Andrew is not only factory-trained, but he's an American Iron racer, and runs the brake tech seminars at the Midwest and Great Lakes NASA region events. He's a wealth of information about braking and braking systems. Oh, and he drives Mustangs! (andrew-racing.com)

All that said, and admitting to no hard data, there's no other reasonable explaination to the phenomena involved... open ducts, no initial bite, but 150-200' into the braking zone, they're back up to normal. Restricted ducts, and the initial bite is there, no pad fade anywhere on track, and bleeding is prophylactic in nature, rather than to remove boiled fluid.

I've raced RA about eight times (mostly, at the Kohler Challenge).

How do you note rotor/pad temps? Do you come in the pits and do a quick measurement? Or do you have a data system that downloads temps from the car sensors' extra computer?

Jay has done some IR temps on my car, not at RA, but at Blackhawk, and we've seen regular readings in excess of 950*F ducking into the hot pits with no cool down. Jay's best (educated) guess is that I'm seeing an additional 150* or so while in the braking zone, which explains why my car just loves the DTC compounds, but eats up the less aggressive ones in a hurry.

Yes, there are three straights at RA:
1) The main straight goes into T-1. It's a fast turn. no problem here.
2) The Morainne Sweep into T-5 is very fast (it's downhill).
3) The rear straight is very difficult. If you go through The Carousel (T-9 and T-10) perfectly and through The Kink (T-11) wide-open, and through Kettle Bottoms, we find Canada Corner (T-12) to be a problem.

My following narritive is based on data from my last session up at RA. The session in question was the second session of the weekend, while I was still working on a couple of things, and had a 260lb instructor and 40lbs of seat and harnesses in the passenger side of the car. Despite all that, and running it around 85-90%, the best lap was a 2:42.588, just a tick under two seconds off the TTB lap record of 2:40.630. Oh, and it was on a set of Hoosier R6 rubber with 12 heat cycles on them and one showing cords... Following the described lap, I blew the slave cylinder during the 5/4 downshift into T1, and that ended my weekend. Getting around with no power to plant the rear was... intersting...

T1: In at 138mph, with massive tire shake, had to brake early@ 0.80G and run a rim-shot to allow space for a car coming out of the pits. Speed down to a miserable 60mph at "apex". Got a good exit, though, so the rest of the lap was salvageable.
T5: In at 133mph, pulled 0.89G doing the 4-3 and 3-2 downshifts, and ran through at 44mph pulling 1.26G, and got a good exit, getting on the power hard right at apex.
I fought a bit of a push condition through The Carousel from the extra weight, and sort of took it easy through The Kink (1.18G at 109mph), not wanting to push through and contribute any silver paint to the wall...
T12 (Canada Corner) was a 130mph entry, braking at 0.94G and trail-braking for 80, on the power and then just touched 1.06G apexing at 54MPH. I run a slightly different line through there, sacrificing a touch of speed here to get the setup I want for what used to be the Billy Mitchell bridge turn (T13). I also remember blowing that corner a bit, not hitting the apex cleanly.

If we break it down this way, the braking energy involved is more apparent:
T1: 138 down to 60: Panic stop from 89mph. This follows a 3025' straight.
T5: 133 down to 44: Panic stop from 78mph, following a 3888' straight.
T12: 130 down to 54: Panic stop from 76mph, following a 2736' straight.

All of this was done carrying an off-center 300lbs of ballast, on fairly worn-out tires, with traffic. This cost me an easy 3-5mph through each corner.

Now, let's compare that to Blackhawk Farms, where I have a personal best lap of 1:20.728. Distances given are brake-off to brake-on, just to scale it to the straights at RA. TRACK MAP

T1: 113mph down to 58 at 0.82G, through at a touch over 1.10G. 1227' to the T3 braking zone.
T2: Flat-out at 1.15G and 95mph.
T3: 98 down to 63 at .76G with trailbraking, apex at 1.10G. 532' later:
T3d: 86 down to 50, 0.80G trailbraking, apex at 1.09G. 436' later:
T4: Tap the brakes to plant the front tires (.38G, 66 to 58), apex at 1.25G. 1222' to the T6 braking zone.
T5: No brakes, just a lift (75 to 73mph), 1.29G apex on the sweeper.
T6: 0.83G braking 99 to 53, 1.10G apex. 1814' later:
T7: 0.92G braking, 111 down to 47, pulling 0.75G through the T6a kink immediately preceding the braking zone. 1542' to the T1 braking zone.

Given that all happens in 80 seconds, there really isn't that much recovery time between braking events. If you factor in "good air," for the ducts, though, it gets worse. There are only four segments on the track that I'm not pulling AT LEAST 0.50G lateral, which means the car is not head-on into the airflow, but at some sort of (slip) angle.

T2-T3: 147' under 1/2G, then a 35mph panic stop.
T5-T6: 134' under 1/2G then a 46mph panic stop.
T6-T6a: 520' under 1/2G then a 64mph panic stop.
T7-T1: 1482' under 1/2G, then a 55mph panic stop.

That means a total of 2283' of actual straight per lap. That's less than the distance between The Kink and Canada Corner at RA.

My braking package is pretty well set up for tracks like Blackhawk, which can turn pads into cinders in a heartbeat. I had a intermediate-level student that burned through two sets of (NAPA) brake pads in 80 minutes. All I'm saying is that I may be getting a bit too much cooling at a track like RA.

EDIT: Hippopotamus discussion:

Yet, at RA in those three turns, there is a big gravel trap at the end. RA has a roll-back at these turns. They'll pull you out without losing a lap.

I would never recommend hippopotamus braking in The Boot at Watkins Glen. There is just one good gravel trap there. The rest is pure guard rails. One mistake there, and you car is slapping some major hard armco.

I can't in good faith recommend that anybody even consider using the gravel traps in an effort to improve their driving on-track... Too many bad things can happen in them, and realistically, they're there to save your life in the event of something just going horribly wrong, not catch the car while you're trying to push the braking envelope. Late braking can save you a few hundredths if you pull it off, but it will cost you tenths, seconds, or even minutes if you botch it. Then there's this:



The bottom line for me is that EVERY car is faster on asphalt than it is in the grass, dirt, or pea gravel... Plus, if you get in the gravel, you'll NEVER get all of it out of car, no matter HOW hard you work at it! Don't ask me how I know

NASA will be up at RA in October, you should come play with us! If you have a comp license (SCCA?) they'll port you right in, assuming correct safety gear. If you don't have the comp license and/or safety gear, come run TT with us, it'll be a blast having some more old iron on track with the newer cars! PM me if you have any Q's or issues getting registered up.

 

[knownukes]

I like DTC70's up front and DTC60's in back. Make sure not to mix pads on the same rotors.

+1 I run the same setup and never get even a soft pedal with an 800+ hp car.

 

[fordrocks]

Great useful information here.

 

[DusterRT]

This would probably be a good supplement to Dave's insight:

http://www.s197forum.com/forum/showthread.php?t=39915

 

[almost heaven]

Awesome analysis Dave! Thanks for sharing, as always.

 

[Sky Render]

This thread should be a sticky.

 

[RolloTomassi]

I don't know anyone who can't put things more clearly for us rookies than you Dave.

One thing I might add is a note on practicality. If you are running air ducts on a daily driver, be sure to cover them up if it's raining. The last thing you want is to go through a puddle and have purposefully directed water to the back of your rotors.

Not like I've had that happen or anything...

 

[Sleeper_08]

Yesterday I was at a presentation by a brake material supplier representative on their brake pads to an audience primarily of Porsche owners. Their pad materials are used extensively in race cars.

In one of the very first slides he stated in bold red lettering "Brakes don't stop cars, tires do" thus reinforcing what Dave says above.

In the presentation and subsequent Q&A a few other things came out that are relevant to our cars
1) DOT 4 fluid is a must for track use and it needs to be changed and/or bled based on your use of the car. Proper pads for your style of driving and brake cooling will improve track performance.
2) if the stock system is capable of kicking in the ABS on the tires then BBK's will not stop you in a shorter distance. They benefits they can provide are more heat absorption capacity, better quality components and a better pedal feel
3) drilled and/or slotted rotors are not required for today's pad materials
3) don't let your pads get too worn as doing so results in more heat being transferred to the calipers and fluid as the pad material acts as a heat insulator. This is more beneficial with ceramic based pads materials than iron based pad materials
4) running track pads on the street is not necessarily a bad thing, if you can live with the squeal. Even though the pads are operating well below their design temps on initial application the combination of their overall performance and the high performance street tires we run means that under panic braking you more more likely to get hit from behind than hitting the person in front. Especially if you are focusing on your driving and leaving enough distance from the car in front, which we all all do Disclaimer - the pad material you choose to run is up to you and you are responsible for your choice.

 

[pcdrj]

Here's another source of info I've used in the past.

http://www.stoptech.com/tech_info/tech_white_papers.shtml

 

[argonaut]

Here is a link to the article I love to trot out when someone waxes on about how their brand new BBK stops their street car so much better than the OEM system. Its a test done by Zeckhausen racing comparing stopping distances of several different brake systems (OEM base, OEM track, ST 332mm and ST 355mm). Scroll to the bottom and look at the table of summary data. The data backs up exactly what this whole thread is stating - the stopping distances (100 - 0) between the various systems are almost a wash. But the rotor temp differences are large - proving once again that big rotors don't stop the car any better but they do provide the other benefits of durability, resistence to fade, etc.

http://www.zeckhausen.com/Testing_Brakes.htm