Scary brake fade/failure
07-19-2006, 06:56 PM
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Scary brake fade/failure
I have always been told CMP was hard on brakes. I got to find it out in person.
We only got two sessions on Saturday due to weather. Therefore, I half decided, half forgot to bleed my brakes Saturday night. (I had already bled the system on Thursday night) Well, 20 minutes into the first session on Sunday I came to the end of the long straight between 7 and 8 at about 110 mph. When I went to brake at the 3, the pedal hit the firewall with a resounding thud. No warning.
Went straight off. First through the grass, then into the sand trap. As I neared the edge of the sand trap and the start of the trees, I spun it left and came to a stop about a car length from the trees. About 5 pounds worth of sand came in the passenger window once the car got sideways.
About 15 minutes later, after the car cooled down, the pedal finally came back. We bled the brakes, got some air out of the front calipers, and I ran 5 problem-free sessions (we got some make-ups for Saturday).
What really got to me was the absolute lack of warning. I had used the brakes very hard at turn one. Then a slight tap at 4 and 5 because I was behind slower traffic. One would assume that the long straight would have given the brakes time to cool, but evidently the fluid had already gotten all it could take.
Even though the pedal was on the floor, a check of my track data shows that I was slowing, though only at about 0.3-0.4 G. Since I was expecting about 0.8-0.9 G worth of braking, obviously that wasn't going to cut it.
Anyway, my front calipers (which had changed from gold to maroon long ago) are now basically black.
I guess it is time for some ducting/further cooling up front.
Sean
We only got two sessions on Saturday due to weather. Therefore, I half decided, half forgot to bleed my brakes Saturday night. (I had already bled the system on Thursday night) Well, 20 minutes into the first session on Sunday I came to the end of the long straight between 7 and 8 at about 110 mph. When I went to brake at the 3, the pedal hit the firewall with a resounding thud. No warning.
Went straight off. First through the grass, then into the sand trap. As I neared the edge of the sand trap and the start of the trees, I spun it left and came to a stop about a car length from the trees. About 5 pounds worth of sand came in the passenger window once the car got sideways.
About 15 minutes later, after the car cooled down, the pedal finally came back. We bled the brakes, got some air out of the front calipers, and I ran 5 problem-free sessions (we got some make-ups for Saturday).
What really got to me was the absolute lack of warning. I had used the brakes very hard at turn one. Then a slight tap at 4 and 5 because I was behind slower traffic. One would assume that the long straight would have given the brakes time to cool, but evidently the fluid had already gotten all it could take.
Even though the pedal was on the floor, a check of my track data shows that I was slowing, though only at about 0.3-0.4 G. Since I was expecting about 0.8-0.9 G worth of braking, obviously that wasn't going to cut it.
Anyway, my front calipers (which had changed from gold to maroon long ago) are now basically black.
I guess it is time for some ducting/further cooling up front.
Sean
07-19-2006, 07:11 PM
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damn!
i had a brake issue going into that same turn at CMP i forget how fast i was running probably close 110 and there was a M3 infront of me that was slowing for the turn i go to hit my brakes and NOTHING HAPPENS! finally i pumped them a few times and it slowed but none the less scary.
i pull off the track to find that i wore my rear pads down to the backing plates in the first session and cooked my calipers to a nice and ugly burnt bronze!
but no off track for me. i only did that once at rockingham infeild and i swear there was slick spot on the track
was that your first time off?
i had a brake issue going into that same turn at CMP i forget how fast i was running probably close 110 and there was a M3 infront of me that was slowing for the turn i go to hit my brakes and NOTHING HAPPENS! finally i pumped them a few times and it slowed but none the less scary.
i pull off the track to find that i wore my rear pads down to the backing plates in the first session and cooked my calipers to a nice and ugly burnt bronze!
but no off track for me. i only did that once at rockingham infeild and i swear there was slick spot on the track
was that your first time off?
Last edited by **; 07-20-2006 at 02:39 AM.
07-20-2006, 11:56 AM
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That was my first "out of control" off. I had had 2 very uneventful off's before in my track driving experience (13 weekends) where I knew I was too hot for a corner and simply drove off and back on. No big deal. This, however, certainly felt like a big deal at the time. I'm glad I can talk about it now as being no big deal, but it was very close to being a bad one.
Fluid: Ate Super Blue
Pads: Front - PFC 01
Rear - Carbotech XP-9
I have removed my dust shields. It's weird. The inner half of the calipers already seem to get alot better cooling than the outer half. All the discoloration is on the outer half. Therefore, I don't know how effective extra cooling would actually be.
I doubt I will be doing RA. Probably won't be on track again until Sept.
Sean
Fluid: Ate Super Blue
Pads: Front - PFC 01
Rear - Carbotech XP-9
I have removed my dust shields. It's weird. The inner half of the calipers already seem to get alot better cooling than the outer half. All the discoloration is on the outer half. Therefore, I don't know how effective extra cooling would actually be.
I doubt I will be doing RA. Probably won't be on track again until Sept.
Sean
07-20-2006, 12:25 PM
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Did you pump the pedal after it went to the floor?
Are you certain you had brake fade and not pad knockback? Was there a hard turn before this brake zone?
After hard cornering the hub flex in our cars pushes the pads outwards. I have to pump the brakes lightly with my left foot to get my pedal back sometimes after cornering. At thunderhill and Laguna Seca, we have hard brake zones after barreling down the front straight. I always make sure to pump my brakes back up before the brake zone into turn one.
Just a thought. I think I started a thread on this a while back.
Are you certain you had brake fade and not pad knockback? Was there a hard turn before this brake zone?
After hard cornering the hub flex in our cars pushes the pads outwards. I have to pump the brakes lightly with my left foot to get my pedal back sometimes after cornering. At thunderhill and Laguna Seca, we have hard brake zones after barreling down the front straight. I always make sure to pump my brakes back up before the brake zone into turn one.
Just a thought. I think I started a thread on this a while back.
Last edited by daveh; 07-20-2006 at 12:28 PM.
07-20-2006, 12:55 PM
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Oh yeah. I pumped it. The pedal went to the floor during every application for about the next 10 minutes after I went off. It was back to being rock hard about 15 minutes later.
There was a long sweeper before the straight, but it wasn't pad knockback. I have experienced it before (ex. at the end of the back straight at VIR after going through Oak Tree), and this wasn't it.
I got some bubbles out of the front calipers afterwards, so I boiled the fluid.
Sean
There was a long sweeper before the straight, but it wasn't pad knockback. I have experienced it before (ex. at the end of the back straight at VIR after going through Oak Tree), and this wasn't it.
I got some bubbles out of the front calipers afterwards, so I boiled the fluid.
Sean
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07-20-2006, 01:35 PM
#8
I does sound like you boiled your fluids. ATE is pretty good fluid. But, how old is it? When you bled, and topped it off, did you put in fluid from a sealed container? Since ATE comes in a bargain 1L can, it's not uncommon that folks keep it sitting around for months (I'm guilty of that). If your fluid is old, then you basically only have thermal capacity at it's wet boiling point.
I haven't flushed my fluids for a year. I should probably thank you for posting this, and getting me to flush it completely at least once a year. I'm using Motul, but have used ATE with no problems before.
I haven't flushed my fluids for a year. I should probably thank you for posting this, and getting me to flush it completely at least once a year. I'm using Motul, but have used ATE with no problems before.
07-20-2006, 01:37 PM
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Wow that sounds scary. I use motul fluid because it has a slightly higher dry boiling point than the blue stuff, but if you boiled it that bad I'm not sure it would have made a difference.
I also installed some ducting to keep my stoptech's cooler and am waiting for my titanium backing plates to come in.
Good luck.
I also installed some ducting to keep my stoptech's cooler and am waiting for my titanium backing plates to come in.
Good luck.
07-20-2006, 02:14 PM
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i do have to admit that the fluid wasn't fresh. it had been in my garage for about 9 months, so that is probably part of the issue.
the fluid i replaced it with on sunday after the incident was brand new. and it obviously had no problems (of course i probably never got back past 6/10ths for the remaining sessions).
sean
the fluid i replaced it with on sunday after the incident was brand new. and it obviously had no problems (of course i probably never got back past 6/10ths for the remaining sessions).
sean
07-21-2006, 05:27 AM
#11
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Sorry to hear about the off, but definitely glad you're okay.
I've learned that Motul, while having a higher boiling point, also absorbs water from the air more quickly/readily than most other high temp fluids, and thus needs to be changed more often. This might have contributed to your experience.
Again, glad you're allright. Having experienced brake problems myself (pad fade), I know how scary it can be.
I've learned that Motul, while having a higher boiling point, also absorbs water from the air more quickly/readily than most other high temp fluids, and thus needs to be changed more often. This might have contributed to your experience.
Again, glad you're allright. Having experienced brake problems myself (pad fade), I know how scary it can be.
07-21-2006, 06:02 AM
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When checking the boiling point of the brake fluid, most manufactures list a dry boiling point and a wet boiling point. Look at the wet boiling point. Since it is impossible to keep moisture out of the braking system, it is the wet boiling point that is important. You will notice some brake fluids have very high dry boiling points but lower wet boiling points than other fluids. I would recommend going to the Castrol SRF, it has the highest wet boiling point of any fluid available. Its expensive but worth it. I have never had a problem boiling fluid in any of my racecars using SRF.
Also, you should change the fluid more than every 9 months. I would recommend a heavy bleed after every track day. This will keep the fluid continually fresh.
Also, you should change the fluid more than every 9 months. I would recommend a heavy bleed after every track day. This will keep the fluid continually fresh.
07-21-2006, 11:10 AM
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the fluid in the car was fresh, as far as the car was concerned. like we are getting at now, the fluid was probably 9 months old, and had been opened before. i'm sure it just sat there sucking in moisture and waiting to let go on me.
when i put in the brand new stuff (opened just before pouring it in), everything worked great.
when i put in the brand new stuff (opened just before pouring it in), everything worked great.
07-21-2006, 12:47 PM
#14
Originally Posted by ALong
When checking the boiling point of the brake fluid, most manufactures list a dry boiling point and a wet boiling point. Look at the wet boiling point. Since it is impossible to keep moisture out of the braking system, it is the wet boiling point that is important. You will notice some brake fluids have very high dry boiling points but lower wet boiling points than other fluids. I would recommend going to the Castrol SRF, it has the highest wet boiling point of any fluid available. Its expensive but worth it. I have never had a problem boiling fluid in any of my racecars using SRF.
Also, you should change the fluid more than every 9 months. I would recommend a heavy bleed after every track day. This will keep the fluid continually fresh.
Also, you should change the fluid more than every 9 months. I would recommend a heavy bleed after every track day. This will keep the fluid continually fresh.
The time I spend bleeding (and sometimes flushing) could easily justify the price of SRF.
Why haven't I gone with SRF? Well, I'm not quite convinced that you can go a full season (assuming 12 track days) without bleeding it. I'm just relaying experience from other DE folks on other forums. Also, I'm not sure if SRF is compatible with our brake system; is it Along?
07-21-2006, 03:50 PM
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I'm uploading the in-car video to Google now. I'll post it. I was scared for you man. You went a LONG way off track. I know you were going fast going toward turn 8.
07-24-2006, 12:15 PM
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Here's the video of the brake failure. Keep in mind I was 2 cars back, but you can see most of the off. You can't see the final resting spot with the car sideways due to the dust cloud.
http://video.google.com/videoplay?do...37840046&hl=en
Also, here's a video of a whole afternoon session.
It's 15 minutes:
http://video.google.com/videoplay?do...08702060&hl=en
http://video.google.com/videoplay?do...37840046&hl=en
Also, here's a video of a whole afternoon session.
It's 15 minutes:
http://video.google.com/videoplay?do...08702060&hl=en
07-24-2006, 05:02 PM
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thanks, levent.
at least it looks cool. you can't even really tell there is a car there.
it appears that i left skid marks on my way off. must have been from my rear tires, as all the air came out of the front calipers so it must have been the fronts that weren't grabbing.
also...what's funny about the full session vid (which is a couple of sessions after i had gone off) is how early and conservatively i am braking, just in case it happened again. really slowed me down.
at least my car sounds great the little while you are behind it.
sean
at least it looks cool. you can't even really tell there is a car there.
it appears that i left skid marks on my way off. must have been from my rear tires, as all the air came out of the front calipers so it must have been the fronts that weren't grabbing.
also...what's funny about the full session vid (which is a couple of sessions after i had gone off) is how early and conservatively i am braking, just in case it happened again. really slowed me down.
at least my car sounds great the little while you are behind it.
sean
07-24-2006, 05:06 PM
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Yes, you could hear your exhaust over mine. It was fun playing at CMP. We'll have to do it again. You going to Road Atlanta? I'll be there, but I'll be taking the old RX-7 in HPDE 2 instead of the RX-8 in HPDE 3.