Brake failure strategies
06-23-2018, 02:33 AM
#1
Burning Brakes
Thread Starter
Brake failure strategies
The tragedy at Mosport got me thinking about this again, but I didn't want to sidetrack that thread. My question to the more seasoned racers out there is, aside the need to have a mentally-practiced brake failure strategy for every corner on the track, what should that be? Obviously if there is available runoff,
it's a matter of getting to it without wiping out the corner workers. But what about no runoff
turns like Laguna T11 or Sears T11? I assume one would just try to get the maximum deflection angle possible on impact? Maybe put the car into a spin to get some friction slowing and roll the dice vs. certain frontal impact? What if it happened entering Laguna T8? Better to go straight into the tires or to steer left and fly into the abyss?
it's a matter of getting to it without wiping out the corner workers. But what about no runoff
turns like Laguna T11 or Sears T11? I assume one would just try to get the maximum deflection angle possible on impact? Maybe put the car into a spin to get some friction slowing and roll the dice vs. certain frontal impact? What if it happened entering Laguna T8? Better to go straight into the tires or to steer left and fly into the abyss?
06-23-2018, 08:57 AM
#2
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Mglobe should post his MX5 Cup COTA brake failure video here
I gently left foot tap the brake pedal before every brake zone on every track. Not only does it get rid of any pad knockback, but I tells me whether I'll have brakes
I gently left foot tap the brake pedal before every brake zone on every track. Not only does it get rid of any pad knockback, but I tells me whether I'll have brakes
06-23-2018, 08:59 AM
#3
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The number one thing is to implement strategies that lessen the likelihood of this occurrence.
One of If which is to, with your left toe, tap the pedal once or twice before the big brake zones to make sure you have pressure.
So many failures have nothing to do with hydraulic failure but are the result of hub bearings going bad or other “pad knockback” causes. The driver goes to the brakes and there’s nothing there, but if they hit it again, it pumps up (because the vehicle is in a straight line) and the brakes work. Good habit. Every pro I know who has experienced failure does this automatically.
Second is have a plan. When Mario Andretti was asked how many straights there are at a track, he said, “an infinite number.”
Also, back in. Better head and neck support.
One of If which is to, with your left toe, tap the pedal once or twice before the big brake zones to make sure you have pressure.
So many failures have nothing to do with hydraulic failure but are the result of hub bearings going bad or other “pad knockback” causes. The driver goes to the brakes and there’s nothing there, but if they hit it again, it pumps up (because the vehicle is in a straight line) and the brakes work. Good habit. Every pro I know who has experienced failure does this automatically.
Second is have a plan. When Mario Andretti was asked how many straights there are at a track, he said, “an infinite number.”
Also, back in. Better head and neck support.
06-23-2018, 05:08 PM
#4
The only time I watch NASCAR on TV is when they're at the Glen, and when they show in-car footage you invariably see all of those guys pumping the pedal all over the track as Dave and Peter have stated.
Myself, I alleviate the need for that practice by not braking whenever possible
Gary
Myself, I alleviate the need for that practice by not braking whenever possible
Gary
06-23-2018, 06:59 PM
#6
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06-23-2018, 08:08 PM
#8
Three Wheelin'
Can we do that in street gt3 and rs cars on trackdays too ? I mean, isn't there some electronics going bananas when we apply throttle and brake together ? I recall threads about brake problems with left foot brakers that had slight overlap in throttle and brake applications. Doing the brake tap check wouldn't be too dissimilar to that ?
06-23-2018, 08:22 PM
#9
Originally Posted by bccars
Can we do that in street gt3 and rs cars on trackdays too ? I mean, isn't there some electronics going bananas when we apply throttle and brake together ? I recall threads about brake problems with left foot brakers that had slight overlap in throttle and brake applications. Doing the brake tap check wouldn't be too dissimilar to that ?
06-23-2018, 08:54 PM
#10
Rennlist Member
With modern Porsches, you have about 2/3 of a second before the computer cuts the ignition. All you really need is a momentary toe tap to make sure there is a bit of resistance I.e. Brake pressure. Much less than 2/3 of a second
06-23-2018, 09:41 PM
#11
Pad knockback is a problem but not a brake failure mode. The brakes are there, just you either anti-knock back before the brakezone or pump at the brakezone to get your full pedal back. Racers should be able to feel the result of knockback as they build speed and know what braking zones will require anti-knockback efforts. The side-effect might be some minor security that you might have brakes but really a racer wants to take up the knockback but not slow the car so you really aren't "testing" for brakes. If you actually are testing for brakes before the brakezone you are slowing the car. Pros are bending stuff more and opening up tolerances so have more knockback to deal with at higher limits. That's why you can be fine on the street but have knockback suddenly appear on the track. So the pro wants 100% pedal so he has to take up the slack but he isn't braking. He still has no idea if he will have a brake failure like a line popping off or a master cylinder seal blowing out or a rotor explosion.
I think the best mitigation for brake failure is to have headroom in your brake system and select the right compromises in brakes before you ever get on track. But lots of headroom is more weight. You are at limits if you need big cooling ducts, SRF fluid, and a post session bleed and "need" anti-knockback measures with pad and rotor changes after a weekend. That is a system that will fail you. Sometimes rules give you no choice. You want head room like it is OK if a plastic bag gets stuck in your left cooling duct. Your rotors survive multiple weekends even over a year. You got a good system when you can use the cheapest autoparts Dot3/4 and be fine or just bleed before your race weekend and never have to touch your system. Then if you use the best fluids and bleed often and take care of the brake system it is even less likely to fail.
Brake brand is not an issue but brake capacity for the application. But there are some brands like AP who understand the race compromises and might be able to set you up with a better system than another brand seen mostly on hot streetcars that rarely hit the track.
Some SS brake lines are not DOT. It is very hard for a SS line to pass the DOT whip test that rubber easily passes. Stoptech for example makes their own SS lines and they are DOT.
If your friends all have severe pad taper with 4 pot calipers consider going to a 6 pot. That reduces the taper and knockback.
use tempilaq indicator paint to make sure you select the right pad in the right operational range to prevent pad damage
Inspect pads for faults before installation and be mindful of install errors like incomplete piston imprint on backing plates due to piston dust boot entrapment.
Having friends race the same car with similar equipment you start to see the failures and you can get in front of failures by having a plan for replacement and service. When is the last time you rebuilt your calipers?
Prior to 2010 we had a huge problem getting the stock brakes to live. Our petitions for aftermarket brake upgrades fell on deaf ears. One year a driver was airlifted out because of brake failure. Finally, we were given brakes and the knee-jerk so severe that I went from changing rotors every weekend to system with such capacity I change rotors every other year! So stay on your sanctioning bodies and keep after them for your safety.
I think the best mitigation for brake failure is to have headroom in your brake system and select the right compromises in brakes before you ever get on track. But lots of headroom is more weight. You are at limits if you need big cooling ducts, SRF fluid, and a post session bleed and "need" anti-knockback measures with pad and rotor changes after a weekend. That is a system that will fail you. Sometimes rules give you no choice. You want head room like it is OK if a plastic bag gets stuck in your left cooling duct. Your rotors survive multiple weekends even over a year. You got a good system when you can use the cheapest autoparts Dot3/4 and be fine or just bleed before your race weekend and never have to touch your system. Then if you use the best fluids and bleed often and take care of the brake system it is even less likely to fail.
Brake brand is not an issue but brake capacity for the application. But there are some brands like AP who understand the race compromises and might be able to set you up with a better system than another brand seen mostly on hot streetcars that rarely hit the track.
Some SS brake lines are not DOT. It is very hard for a SS line to pass the DOT whip test that rubber easily passes. Stoptech for example makes their own SS lines and they are DOT.
If your friends all have severe pad taper with 4 pot calipers consider going to a 6 pot. That reduces the taper and knockback.
use tempilaq indicator paint to make sure you select the right pad in the right operational range to prevent pad damage
Inspect pads for faults before installation and be mindful of install errors like incomplete piston imprint on backing plates due to piston dust boot entrapment.
Having friends race the same car with similar equipment you start to see the failures and you can get in front of failures by having a plan for replacement and service. When is the last time you rebuilt your calipers?
Prior to 2010 we had a huge problem getting the stock brakes to live. Our petitions for aftermarket brake upgrades fell on deaf ears. One year a driver was airlifted out because of brake failure. Finally, we were given brakes and the knee-jerk so severe that I went from changing rotors every weekend to system with such capacity I change rotors every other year! So stay on your sanctioning bodies and keep after them for your safety.
06-23-2018, 11:03 PM
#12
Rennlist Member
Can we do that in street gt3 and rs cars on trackdays too ? I mean, isn't there some electronics going bananas when we apply throttle and brake together ? I recall threads about brake problems with left foot brakers that had slight overlap in throttle and brake applications. Doing the brake tap check wouldn't be too dissimilar to that ?
06-24-2018, 10:54 AM
#13
Three Wheelin'
I do a brake check before every major braking zone. But from my own experience, a quick tap doesn't always let you know of a brake failure. I had a brake failure a number of years ago on my 914/6 racecar. I did a brake check like usual on the straight just before my brake failure at the end of the front straight at Lime Rock. I will never know whether the brake check felt "fine" because the brakes hadn't failed yet, or because the brake check was a light enough tap that I couldn't detect the brake failure. In my case, a bridge line failure on one of the front calipers. The front brakes seemed to be essentially not working when I got to the brake zone, but perhaps gave enough pressure to not be detectable when I did the brake check ...
06-24-2018, 02:40 PM
#14
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FBB, we're not talking about the usual "pad knockback" here, we're talking about when everything's good and the then it isn't...
If a hub bearing failed or the fixing nut came loose, it would allow the rotor to wobble and you could have no movement for the whole race and the one time you go for the brakes, not only are they not there, they can't be quickly pumped up because the rotor's wobbling around loose in the upright.
That is alot of what I see, that and bleeder nipples coming loose, banjo bolts coming loose, lines abraided and then cut or bursting hydraulically...
If a hub bearing failed or the fixing nut came loose, it would allow the rotor to wobble and you could have no movement for the whole race and the one time you go for the brakes, not only are they not there, they can't be quickly pumped up because the rotor's wobbling around loose in the upright.
That is alot of what I see, that and bleeder nipples coming loose, banjo bolts coming loose, lines abraided and then cut or bursting hydraulically...
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06-24-2018, 03:43 PM
#15
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Just when I figured out how to heel/toe you want me to do this?!
Actually, my coach has been after me to do this for pad knockback forever but I can't seem to get in the habit. Next DE I am going to have to give it a try.
Actually, my coach has been after me to do this for pad knockback forever but I can't seem to get in the habit. Next DE I am going to have to give it a try.