S197 Losing brakes during autocross

[drj2k1]

After a disappointing weekend autocrossing, I'm hopeful that TMO might be able provide some insight towards rectifying a brake system issue that has occurred twice now under the stress of autocross. For the second time under my ownership, my 2011 V6 PP has overheated its brakes during autocross resulting in the pedal dropping to the floor mid-run.

Previously in the the Fall of 2019 we were racing up in Fairfield on a 40 degree day, stock Mustang GT brakes (non Brembo) with OE Ford pads/rotors/fluid), two drivers sharing the car. Event field was pretty small and we were essentially put in a position where we were hot-lapping the car during the same heat. Began to experienced fade after 4-5 runs, let the car cool down in grid for a little then completely lost the pedal on the next run. Upon examination the brake fluid was blackened.

Following this situation we updated the braking system with centric rotors, Porterfield R4-S pads, and ATE Type 200 DOT 4 Racing Fluid. The brakes were strong in our first event in the car of this season, no noticeable fade and the brake issue was seemingly rectified. Fast forward to event #2 this weekend on a very fast course (again with a tight run group that had us hot lapping the car with two drivers) and we lost the brake pedal again after 6 runs.

Run Video with brakes:

Run Video without brakes:

I've never experienced or heard of brake failure like this in an autocross application before, but I think the real issue is lack of airflow to the brakes which is exacerbating the "small-ish" brakes on a 3400lb car. Ducting the brakes is more than likely the solution, but would take me outside out my classification.

Seeing as we are limited in our modifications to the braking system to pads and fluid, I've found myself at a cross-roads with the build of the car: find a solution to the brake system within the rules, duct the brakes and/or upgrade to Brembos (necessitating a move up to a big boy class like CAM), or sell it for a more competitive platform. Not exactly where I expected to find myself 2 events into the season.

My initial thoughts upon researching the issue on TMO are to re-flush the brakes with a higher temperature fluid like Motul 660F or Castrol SRF ($$$) and possibly utilize titanium shims on the pads (hardbrakes.com has a set for 05-06 mustang calipers that might fit).

Hoping that TMO might have some creative insight as to resolving this issue within the limited ruleset before I throw money at a solution that won't necessarily mitigate the braking issue. I want the car to be safe for my father & I to co-drive so we can salvage what is left of the 2020 season.

Thanks in advance,
J

 

[TMSBOSS]

You might try titanium “squeak” shims to help keep the fluid cool
An upgrade from the ATE would also be a good idea. Motul or Castrol both make fluids which should take More heat. I started with ATE and also boiled that fluid. Castrol fixes that problem for me
Good luck

 

[Boss4Me]

After a disappointing weekend autocrossing, I'm hopeful that TMO might be able provide some insight towards rectifying a brake system issue that has occurred twice now under the stress of autocross. For the second time under my ownership, my 2011 V6 PP has overheated its brakes during autocross resulting in the pedal dropping to the floor mid-run.

Previously in the the Fall of 2019 we were racing up in Fairfield on a 40 degree day, stock Mustang GT brakes (non Brembo) with OE Ford pads/rotors/fluid), two drivers sharing the car. Event field was pretty small and we were essentially put in a position where we were hot-lapping the car during the same heat. Began to experienced fade after 4-5 runs, let the car cool down in grid for a little then completely lost the pedal on the next run. Upon examination the brake fluid was blackened.

Following this situation we updated the braking system with centric rotors, Porterfield R4-S pads, and ATE Type 200 DOT 4 Racing Fluid. The brakes were strong in our first event in the car of this season, no noticeable fade and the brake issue was seemingly rectified. Fast forward to event #2 this weekend on a very fast course (again with a tight run group that had us hot lapping the car with two drivers) and we lost the brake pedal again after 6 runs.

Run Video with brakes:

Run Video without brakes:

I've never experienced or heard of brake failure like this in an autocross application before, but I think the real issue is lack of airflow to the brakes which is exacerbating the "small-ish" brakes on a 3400lb car. Ducting the brakes is more than likely the solution, but would take me outside out my classification.

Seeing as we are limited in our modifications to the braking system to pads and fluid, I've found myself at a cross-roads with the build of the car: find a solution to the brake system within the rules, duct the brakes and/or upgrade to Brembos (necessitating a move up to a big boy class like CAM), or sell it for a more competitive platform. Not exactly where I expected to find myself 2 events into the season.

My initial thoughts upon researching the issue on TMO are to re-flush the brakes with a higher temperature fluid like Motul 660F or Castrol SRF ($$$) and possibly utilize titanium shims on the pads (hardbrakes.com has a set for 05-06 mustang calipers that might fit).

Hoping that TMO might have some creative insight as to resolving this issue within the limited ruleset before I throw money at a solution that won't necessarily mitigate the braking issue. I want the car to be safe for my father & I to co-drive so we can salvage what is left of the 2020 season.

Thanks in advance,
J

I have similar experience with fluid upgrade to from ATE and titanium shields. I finally had first track day this year and only brake change made from prior year was titanium shields and seemed to be directional improvement with fluid reaction.

 

[Norm Peterson]

Hoping that TMO might have some creative insight as to resolving this issue within the limited ruleset before I throw money at a solution that won't necessarily mitigate the braking issue. I want the car to be safe for my father & I to co-drive so we can salvage what is left of the 2020 season.

Thanks in advance,
J

In a previous life I was working a corner station when an off-course car was suddenly headed straight at us . . . good thing he was able to stop, else it'd have been a guessing game as far as the direction none of us went off in was concerned.

So I see brake cooling ducts as being a safety thing, perhaps even more in the spirit of safety than brake pad formulations being unrestricted or the "one sway bar" allowance. Brake cooling is allowed in the ST classes.


Norm

 

[Norm Peterson]

I have similar experience with fluid upgrade to from ATE and titanium shields. I finally had first track day this year and only brake change made from prior year was titanium shields and seemed to be directional improvement with fluid reaction.

I wonder if for the Street Category you'd want or need to get a clarification on those Ti shims. They aren't exactly OE or factory shop manual items.

That said, they should be allowed in the name of safety.


Norm

 

[Mad Hatter]

ATE brake fluid led me to have a serious Holy Crap moment..... SRF and ducts were a great fix

 

[Bill Pemberton]

No one has asked when you changed the fluid last? Sorry but losing the brakes is pretty rare in an Autocross , though like everyone else dump the Fluid and go with Motul or equivalent. There is also a chance there is an air bubble in the lines, too, and considering they are 9 year old rubber lines , in all likelyhood, you might consider a set of Goodridge Stainless steel brake lines ( that used to be legal in the Stock/Street Classes ).

Keep in mind brake fluid is very hygroscopic ( absorbs water ) and without getting into a ton of physics we all know water and oil don't mix. Lots of heat cycles , changes in weather, and lack of changing, can cause problems as the more moisture in the fluid the lower the boiling point. Over the years the number one cause I have seen in new folks losing their brakes is their lack changing the fluid. When I hear of guys going the entire year on track and never changing fluid I get very concerned , because one fast track and no recent change can mean meeting Mr. Wall. So again, when did you change your fluid last and are you on the original lines.

 

[drj2k1]

No one has asked when you changed the fluid last? Sorry but losing the brakes is pretty rare in an Autocross , though like everyone else dump the Fluid and go with Motul or equivalent. There is also a chance there is an air bubble in the lines, too, and considering they are 9 year old rubber lines , in all likelyhood, you might consider a set of Goodridge Stainless steel brake lines ( that used to be legal in the Stock/Street Classes ).

Keep in mind brake fluid is very hygroscopic ( absorbs water ) and without getting into a ton of physics we all know water and oil don't mix. Lots of heat cycles , changes in weather, and lack of changing, can cause problems as the more moisture in the fluid the lower the boiling point. Over the years the number one cause I have seen in new folks losing their brakes is their lack changing the fluid. When I hear of guys going the entire year on track and never changing fluid I get very concerned , because one fast track and no recent change can mean meeting Mr. Wall. So again, when did you change your fluid last and are you on the original lines.

Original Lines are still on the car and old fluid was flushed and bled with 2 bottles of ATE type 200 in April (only two events on the new brakes/fluid). Just doubled checked the SCCA street rules and no braided stainless lines are allowed on cars built after 1992.

 

[DaveW]

Man, there has to be something else going on.

Silly question, but you have traction and stability control completely turned off, right?

DaveW

 

[Fat Boss]

Wait, are you saying you don't have brake ducts on it yet?

 

[302 Hi Pro]

Man, there has to be something else going on.

Silly question, but you have traction and stability control completely turned off, right?

DaveW

Actually a good question b/c it’s so easy to forget to turn the nannies off every time you start the car, especially with multiple drivers.

 

[TMSBOSS]

“Just doubled checked the SCCA street rules and no braided stainless lines are allowed on cars built after 1992.”

No braided lines. So, will the Boss brake lines work? Can they be made to work? They are not braided, just stiffer.

Ford Performance Mustang BOSS 302 Brake Line Upgrade M-2078-MB (05-14 Mustang GT; 11-14 Mustang V6; 07-12 Mustang GT500) - Free Shipping

FREE SHIPPING! Improves Braking. Improve the braking of your Brembo equipped GT with Ford Racing low expansion rubber brake lines from AmericanMuscle. These are

www.americanmuscle.com

Under $100.00.

Listing says 11-14 V-6

 

[drj2k1]

Man, there has to be something else going on.

Silly question, but you have traction and stability control completely turned off, right?

DaveW

Good question Dave,

Usually my father does the first run with traction off/stability on to warm the tires. After his run, we swap drivers, and I shut everything off and it stays off for the rest of the heat. I wonder if the residual heat from built up from the first run with the nannies on is significantly contributing to the problem...

Ordered 2 liters of Motul RBF today to refresh/bleed the system as well as new Ford brake lines to take another variable out of the equation. Next event is July 26th, planning to log brake temps with an infrared thermometer to see how hot things are getting before making any major changes.

Anyone know of any sources to get titanium shims for base GT 2 piston calipers?

J

 

[xr7]

So would it violate the rules if you happened to cut some holes in the facia and if you happened to fashion some sort of deflector mounted on the suspension, ala Vorshlag, that would direct air at the brakes. No ducting involved. Just some good old boys logic for stretching the rules.

Vorshlag S550 Brake Cooling Deflector Kit

Vorshlag has offered "ducted hose" style brake cooling backing plates, inlet ducts, and tubing for a number of cars for many years. This is how you cooled the brakes for track use for many decades. Well there are issues doing that, namely the corrugated hose have some serious flow restrictions...

vorshlag-store.com

 

[Boss4Me]

Good question Dave,

Usually my father does the first run with traction off/stability on to warm the tires. After his run, we swap drivers, and I shut everything off and it stays off for the rest of the heat. I wonder if the residual heat from built up from the first run with the nannies on is significantly contributing to the problem...

Ordered 2 liters of Motul RBF today to refresh/bleed the system as well as new Ford brake lines to take another variable out of the equation. Next event is July 26th, planning to log brake temps with an infrared thermometer to see how hot things are getting before making any major changes.

Anyone know of any sources to get titanium shims for base GT 2 piston calipers?

J

OP Mustang worked for me, a TMO sponsor

 

[blacksheep-1]

my V6 road racer has basically the same setup and rules package, and it's been road raced without issue for years by Heinricy, Rezzatano and Marsh,( all SCCA national champions) if they haven't smoked the brakes on a road course, I don't understand why you would at an autocross. The brakes are bone stock no ducting, braided steel lines, with Hawk pads and AP brake fluid.


Something is not functioning correctly, maybe your Power brake unit, or the antilock.
It might even be massive heat soak, but I have a hard time believing that, when you come off the course, maybe take a run through the paddock and let them cool down a bit

 

[Dave_W]

Watching the second video, it looks like you slow down fine for the right at 0:29 (and the previous turns), but are on the throttle a bit too long before the next left and shoot past the turn-in. I'm not saying overheating the brakes isn't possible in this scenario, but it seems more likely (if you were hard on the brakes there) that the ABS went into "ice mode" or maybe the ABS pump cavitated some old fluid. I've also heard of some stability systems getting confused when both brakes & gas are applied, or more accurately, defaulting to "save the car & driver" mode.

In both videos, there's a lot of noise like gravel in a tin can, and I'm not sure if it's wind noise or sand & tire marbles. If it's sand & marbles, that could be another factor for ice mode on the ABS.

Do you left-foot brake? Are you riding the brake? Or applying gas & brake at the same time? I had an issue in a previous car when I was learning LFB where I'd lose the vacuum assist on the brakes under part throttle, and it felt like the brakes suddenly stopped working. If you LFB and were on the brakes before the right at 0:29, then got back on the gas hard without letting off the brakes much, you might have lost vacuum assist for that next left hander. I have no experience with this in Mustangs, just throwing out ideas.

I was reading up on brake fluids recently, and there's a new-ish DOT 5.1 standard out. This is NOT the DOT 5 that should never, NEVER, ever be used in a street/track car. DOT 5.1 has the same chemistry and dry & wet boiling points as DOT 4, but with thinner viscosity at low/moderate temperatures. Supposedly it's meant for modern ABS systems with small orifices that can have problems with thicker fluids. Prior to DOT 5.1, some brands were specifically marketing a "DOT 4 low viscosity" fluid and DOT 5.1 now puts a formal specification around that. However, some track forums were arguing that while DOT 5.1 may be a good all-weather street fluid, regular DOT 4 can/should still be used on a full track day, as DOT 4 & 5.1 will thin to about the same viscosity at higher temp. I'd argue that's true at the caliper, but not necessarily true at the ABS pump.

PS - How'd the Konis feel? Where did you end up on them?

 

[Bill Pemberton]

Read the rules carefully, but doubt you can do brake ducts , but for an autocross this should not be necessary. Lots of areas to check , but it is confusing because there really is not a reason they should overheat at an autocross. How do the pads look all the way around?

 

[drj2k1]

Watching the second video, it looks like you slow down fine for the right at 0:29 (and the previous turns), but are on the throttle a bit too long before the next left and shoot past the turn-in. I'm not saying overheating the brakes isn't possible in this scenario, but it seems more likely (if you were hard on the brakes there) that the ABS went into "ice mode" or maybe the ABS pump cavitated some old fluid. I've also heard of some stability systems getting confused when both brakes & gas are applied, or more accurately, defaulting to "save the car & driver" mode.

In both videos, there's a lot of noise like gravel in a tin can, and I'm not sure if it's wind noise or sand & tire marbles. If it's sand & marbles, that could be another factor for ice mode on the ABS.

Do you left-foot brake? Are you riding the brake? Or applying gas & brake at the same time? I had an issue in a previous car when I was learning LFB where I'd lose the vacuum assist on the brakes under part throttle, and it felt like the brakes suddenly stopped working. If you LFB and were on the brakes before the right at 0:29, then got back on the gas hard without letting off the brakes much, you might have lost vacuum assist for that next left hander. I have no experience with this in Mustangs, just throwing out ideas.

I was reading up on brake fluids recently, and there's a new-ish DOT 5.1 standard out. This is NOT the DOT 5 that should never, NEVER, ever be used in a street/track car. DOT 5.1 has the same chemistry and dry & wet boiling points as DOT 4, but with thinner viscosity at low/moderate temperatures. Supposedly it's meant for modern ABS systems with small orifices that can have problems with thicker fluids. Prior to DOT 5.1, some brands were specifically marketing a "DOT 4 low viscosity" fluid and DOT 5.1 now puts a formal specification around that. However, some track forums were arguing that while DOT 5.1 may be a good all-weather street fluid, regular DOT 4 can/should still be used on a full track day, as DOT 4 & 5.1 will thin to about the same viscosity at higher temp. I'd argue that's true at the caliper, but not necessarily true at the ABS pump.

PS - How'd the Konis feel? Where did you end up on them?

Dave,

Looking at the brake failure video, my father lost first the brakes at the entry to the left sweeper at 0:23. I agree that he was definitely carrying too much speed into that section, but his lateness coupled with the brake pedal going soft pushed him way outside and off course (he should've been on the left of the 4 cone wall). We've been having some technical issues with the new solo storm software and didn't have it up and running at the event, I wish I could see the braking data on this run.

Metlife does has some marbles on Lot J where we were running, but I'm not sure if this triggered ABS ice mode. We don't left foot brake, so that didn't play a factor in this scenario.

Going to try the Motul RBF600 in the car for this year, never had an issue with ATE Type 200 in any of our other cars, but this is also the heaviest car we've autocrossed.

BTW: Ran the Koni's at a quarter turn off full stiff up front and a half turn off stiff in back. You're insight was spot on, the car was much more composed especially under braking/faster transitions

 

[drj2k1]

Read the rules carefully, but doubt you can do brake ducts , but for an autocross this should not be necessary. Lots of areas to check , but it is confusing because there really is not a reason they should overheat at an autocross. How do the pads look all the way around?

Bill I'm in agreement with you and BS-1, something isn't right. Not going to throw money at the car with ducting and whatnot if an underlying issue is still unsolved. Fluid and brake lines should be here Friday, will pull the brake pads out this weekend when I swap the new lines and see if they glazed like the factory ones or not.