Lost brake pedal on track day, Pad knockback?

When pedal goes to floor did you just ride it to the floor with minimal braking and come in the pits?

Did you go to floor and pump brake pedal and did you get brakes?

You are on street tires?

The big reds are the 993 calipers yes all 4 or just fronts?

Did you bolt red on without regard to master cylinder matching?

 

If that is the case, it likely wasn't the pistons pushed back/ pads spread. One stroke of the brake pedal should take up all the slack. The second push should have produced stopping force.

 

On the bright side, you have an excuse to go do another track day. You have to reproduce the problem to try the 'pumping the pedal' test!

 

I'll be waiting for my invite! I live an hour north of Tampa.

 

Knock back can and does happen with all cars on the track to some extent. You'll see most drivers tap the brake pedal with their left foot, even if not left foot braking, before coming into a brake zone to reset the caliper pistons.

From your description it looks like you overheated the brakes. While the brand and type of brake fluid is normally the culprit, there are lots of other factors that go into brakes overheating including, how severe is the brake zone, distance between braking zones, weight of the car, are you using traction control (which constantly uses the brakes), size of brake calipers, type of brake compound, etc.

Heat doesn't cause knock-back but it gets confusing because you don't get knock back unless you are driving fast which generates heat. So many times it can seem heat related. If you just cruise around the track you don't get overheated and you also don't normally notice knock back.

Knock back is generally caused by turns, vibrations and bumps. Sebring, for example, is notorious for knock back.

If you tap the brakes before a braking zone and it fixes the issue than it is knock back. If it doesn't than overheating is probably the culprit.

 

LV has the right answer.

You need to figure out which it is or even combo. Sometimes there are other less popular failures like failing master or leaking residual pressure valve or failing caliper seals. Problem is the next threshold brake failure could be your last. That means you check everything and go through entire system with shotgun approach Unless you can duplicate the problem safely.

were the calipers new? Yes = less desire to rebuild. Pulled off another car I would rebuild. Brake bleeding two man method is more reliable and better. Many don’t believe that. Pull residual pressure valve make sure it works. Test master does it hold pressure or slowly sink? Test booster too. Check wheel bearings. If you can feel any play they are bad and have larger runout under 3000lb car at speed. Consider improvements if you track, like regular bleeding schedule, better fluids motul 600, brake ducts, 2 piece floating rotors, stainless steel brake lines, higher heat capacity pads, and ti shield shins.

understand limit of solid rotor vs. improvement with a two piece vs. a true floating two piece rotor.

if none of that works you have to go with a better system like stop tech or see what Essex has and consider anti knockback spring in the caliper. Or you are stuck with left foot tap to set the pads before you get to the brake zone if the problem of knock back remains

You are not pushing the Car so should be well with in the capability of stock 355 system. There is some kind of fault for sure.

 

Is the brake fluid the same as what you used before? You probably already know wet boiling point is a key measure of how much heat various brake fluids can handle, so maybe look into a better one. Good luck figuring things out.

 

Rear brakes are rarely the issue for brakes problems except for bias issues. They do not normally manifest as the problems you are describing.

As FatBillyBob stated it can always be a combination of issues and that sometimes becomes a ***** to diagnose.

You can never compare street or autocross use to track use. Trust me - you can almost never replicate brake problems on the street that you experience on the track.

You might try getting temperature stickers for each caliper or have someone with a laser thermometer take your brake temperature the moment you get into the pits.

 

Try Moltul RB660 brake fluid. Also the street style Textar pads probably can’t deal with the brake heat like race pads can.

I haven’t driven FIRM...I’m a Sebring, Homestead guy....Id love to get a few lap at a FIRM though but hear it’s hard on brakes. Sebring is very hard on brakes...but Sebring is hard on everything.

 

Motul is good stuff, and I used it for a bunch of years before switching to Castrol SRF. That is what I use in my Porsche Cayman race car. Never have a fluid boiling issue.

That being said, my brake fluid gets flushed and replaced several times a year. The less variables you have the less things can go wrong.

Agree that race pads are needed.

 

Luigi I also come from the Porsche world and use to do a lot of Chin and PCA track days. Sebring is my home track. I am sure we've seen each other. Plus I know if you from Rennlist too.

I have a 488 now...I do less track events these days so I thought I'd get a Ferrari. I do want to take it to a Chin event and was planning on instructing and just running the Ferrari a few laps in the morning then after lunch session. Will be interesting to see how the Ferrari does compared to my 991 GT3 at Sebring

See ya!

 

Hey mdrums!

Yes, I am on RL a lot. Seems to be more activity over there than here but this is rapidly becoming a place I check.

I was at Sebring just a couple of months ago for the PCA race but it seems a million years ago at this point.

Next time I am at the track I plan on doing some laps in my 328 to see what it can do but I will never really track it. I'm sure you will have fun in your 488.

Hopefully we all get back to the track soon! Be well.

 

Just something to consider about SRF fluid. It is considered the best in that it won't boil. I never use it. Brakes are all about managing heat. It's your car's MV*2. So the faster you go or the heavier the car the more brakes you need. I want the worst part of my bake system to be my fluid. I want to use a mediocre fluid and still have all the brakes I need because I want the warning that a boiling fluid gives (the soft pedal) that I am approaching a limit on braking for that race. I want to have enough head room designed into my brake system so that I can use mediocre fluid. If on the other hand SRF never boils where is the next weak link in your system? Boiling fluid is a good thing. You have plenty of warning something isn't right.

The downside to what I want in a brake system is usually weight! For more capacity that might mean a bigger rotor and more rotating mass or a bigger caliper, or bigger brake ducts adding more drag as examples. So the winners engineer at the limit. The more money at stake the more on the limit they go, the more risk is taken. I'm just a long time club racer with a day job and take no risk.

 

OP-
What you described doesn't sound like knock-back. Knock-back is fixed after a quick hit of the pedal.

Side note: knock-back is much more likely to happen after aggressive curb strikes and on thinner brake pads (due to more piston travel). Start track days with fresh pads.

To me sounds like brake overheating. I would change/bleed fluid, start aggressive track days with new pads (new pads have more material to absorb heat than thinner pads) and always a fresh bleed to insure a firm pedal. This should be done every time before tracking a street car. Brake overheating and fade happens on most street cars during aggressive track sessions-- usually first presents itself after the hardest high speed brake zone on the track. It can be dangerous so its good you caught it.

The most important thing is to be aware as a driver as soon as you first feel a longer brake pedal and/or soft pedal. A soft pedal from overheating can quickly become a a pedal to the floor braking incident if you dont notice the early signs. When you first feel it happening you need to immediately back off and slow down to let them cool and preferably come into the pits. For diagnosis, on track give it some pumps and see if that immediately brings the firm pedal back or if it is a slower progression to a firm pedal.

Street cars, including Ferrari's have no/poor brake cooling and the brakes overheat easily. I have driven my 458 at 2 tracks (Sebring and PBIR) and it happened at both (and I would start with fresh pads, high temp fluid, bleed). The 458 has the same brake system as the 458 Challenge car (which wont have this issue), but the Challenge car has brake cooling ducting (as all race cars do) that specifically directs air over the the brakes to cool them and street cars dont have this.

We get soft pedals all the time on my race cars but only in practice after many sessions and we know it is time for new pads and a bleed. For races we always start with those so its rare to happen in a race ubnless htere is a system failure.

If you want to be safe, have your master brake cylinder checked out as well. Brakes are just too important on track not to make sure everything is tip top.

Congratulations on the hard and aggressive braking, that means you were having fun!

BTW brake overheating/brake fade is likely what killed this guy at PBIR: http://gm5-lkweb.newscyclecloud.com/news/20190628/lawyers-blame-instructor-killed-in-crash-for-lamborghinis-brakes-failing
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KY1e, what pads are you using on the 458?

 

I dont remember what pads I used. I tracked it then bought race cars (due to this and other safety issues) and once I got race cars I never tracked my Fcars or any street car again. At the time I'd have Ferrari do a pre track service and put in new pads, high temp fluid/bleed.

After T7 at Sebring my pedal would get very soft and a couple times was soft enough it went to the floor into T10 where car slowed but I had to go straight onto the run off. At PBIR in the Summer I got brake overheat alarms and would have to end session and let them cool.

I overheated the Fcar brakes so badly at Sebring in the Summer that I changed the surface of the CCM's. Only had 8% wear but had to get all new rotors because they became rough and were tearing thru pads quickly. After that I bought a race car and started racing. It kept progressing (last year did 40 races in IMSA/SRO/Crevantic 24hHour Series)

 

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A similar thing happens to steel brake systems when the wrong pad is overheated on track. We see this with street pads used on track. You can get pad transfer as a smear of overheat pad compound embedded on the rotors. This causes judder. You can sometimes scrape it off with a more aggressive pad to clean it off or sometimes you have to turn the rotors or just trash can them. The worse thing is a newbie not understanding what is now wrong with the brakes because they seem to sort of stop ok. Overheated pads can actually chunk and pieces fall off unknown by the newbie and can lead to a total brake failure. A streetcar can have a 200+ mph top speed and brakes capable of slowing the car but pounding repeatedly on a track at around a 100 mile average speed can often be just too much for the brake system.

this is a failed stock 2019 mustang GT OE pad stock brembo big brakes 20 minute session 1 track day to test the car only 200 miles on the chassis at WSIR a not brake intensive track. The pad is burnt and pieces chucked off. This is an unsafe pad.

 

Ky1e, Sebring is my home track...been tracking there since 2005....most Chin but a lot of PCA too. My idea is to do a Chin day as an instructor and do just a morning session and 1 after lunch. Just to have a little fun in my 488 to open it up and see what it feels like in the corners a little. Definitely not going to run it like I use to run my Porsches. I had read hear that stock pads won't last and to use at least Pagid RSC1 pads. I do not want to get back into shaping pads around just for a couple of fun sessions at a track event. I will definilty switch to Motul RBF660 fluid though.

 

The Fcar can handle Sebring for a normal tracking session but I admit I was going all out and it was Summer.

 

It’s not pad knock back. As mentioned above, the pedal comes back on the second pump, because the pad is literally bumped/knocked away from the piston. This happens for me when I drive up on certain curbing aggressively, and it’s always in the same places. The pedal goes “Long” but just until the piston/pad are again married.

I have unfortunately extensive experienced with soft/long/no pedal (though not in a Ferrari) and at some track you can drive around heating related issues, but I don’t advise it for track days because if you lose brakes entirely, you can hit someone’s car. Be careful.