Brake Overheating
10-22-2002, 02:18 PM
#1
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Brake Overheating
I have an '87 Carrera with relatively stock brake components, although I have added an OG Racing cool brake kit, cryo front rotors, ss brake lines, Super Blue fluid and track pads (currently PF 97). In addition I have removed the dust covers, as the car is almost exclusively used on the track for DEs. My problem is that I frequently encounter brake problems resulting from overheating. I have warped rotors and calipers (yes, calipers!) and consistently cook the rubber boot on the caliper pistons, allowing fluid to leak out onto the pads and rotors. Over the past couple of years, I have replaced the master cylinder, brake lines, front calipers and rotors, and still encounter significant heating problems. The problems occur on all types of tracks, from CMP (which is brutal on brakes) to Roebling (which is not), and with different types of pads (I've used Hawkes, Pagid Blacks and now Performance Friction). I seem to experience normal wear on all eight pads and I don't think my braking technique is that dis-similar from others out there. Has anyone else encountered similar brake problems with a 911 on the track? Any suggestions? Constantly rebuilding/replacing brake components is getting expensive!
10-22-2002, 02:35 PM
#2
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I ran an 87 Carrera for a couple of races and had the same brake issues. It does seem like you have done all you can to reduce cooking the brakes to no avail. One possible thing you could try is to remove the fog lights and let the brake cooling ducts pick up from there rather than scoops mounted low under the car. Short of upgrading calipers and rotors, brake management seems to be key.
HTH! <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />
HTH! <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />
10-22-2002, 03:14 PM
#3
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Patrick, I'd check your system to make sure the tubes aren't clogged with rubber chunks. Don't use those little piece of #$%@* vacuum cleaner scoops that zip tie to the bottom of the A arms. Run the 3" ducting to the front of the car. You want clean, high pressure air. Pop out the turn indicators or the fog lights or get an "under the stock bumper" RSR spoiler with the brake cooling openings. I'd run some kind of mesh over the opening of the hose, too. The OG system, which I assume is from the old Holbert molds should be plenty of cooling for Carrera brakes.
10-22-2002, 03:19 PM
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Patrick, just one more thing. The only caliper warping I've seen was on an SC being raced with silicon brake fluid. The fluid held up fine and just kept taking the heat. He destroyed the front brakes, but the fluid never boiled! <img src="graemlins/c.gif" border="0" alt="[ouch]" />
10-22-2002, 03:46 PM
#5
Race Director
Sounds like it's time for big reds for you!
You're probably bleeding your brakes after each session, so the fluid's probably fine.
Have your tried KFP pads? I like their Magnum (Gold) pads, since they are easy on the rotors. (But your ability may require more braking power!)
-Zoltan.
You're probably bleeding your brakes after each session, so the fluid's probably fine.
Have your tried KFP pads? I like their Magnum (Gold) pads, since they are easy on the rotors. (But your ability may require more braking power!)
-Zoltan.
10-22-2002, 04:09 PM
#6
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Patrick:
The problem is heat sink capability. For track use, the stock Carrera brakes just can't dissipate the heat generated by heavy braking. The rotors just are big enough. I know a guy who is an experienced track driver and instructor who does a lot of drivers ed in an 88 targa. He in one season, he rebuilt his calipers, then replaced them later in the year, in addition to replacing rotors quite frequently. He bit the bullet and installed 930 brakes.
When my 84 Carrera needed new calipers and rotors in 2000, since I was doing a lot of DE, I bit the bullet and installed 993TT brakes (all factory parts (including the rotors) accept for the adapters). I ended up taking the class bump up to E in Club Racing. The plus side is that I am still on the original rotors that came with the kit (though the fronts are about done). This is after 7 races, and lots of DE. No warped rotors. I change out the fluid after every other event.
I look at it this way, if I was still running on stock brakes, I would have gone through at least 3-4 sets of rotors and probably two sets of calipers so the big reds have paid for themselves.
The problem is heat sink capability. For track use, the stock Carrera brakes just can't dissipate the heat generated by heavy braking. The rotors just are big enough. I know a guy who is an experienced track driver and instructor who does a lot of drivers ed in an 88 targa. He in one season, he rebuilt his calipers, then replaced them later in the year, in addition to replacing rotors quite frequently. He bit the bullet and installed 930 brakes.
When my 84 Carrera needed new calipers and rotors in 2000, since I was doing a lot of DE, I bit the bullet and installed 993TT brakes (all factory parts (including the rotors) accept for the adapters). I ended up taking the class bump up to E in Club Racing. The plus side is that I am still on the original rotors that came with the kit (though the fronts are about done). This is after 7 races, and lots of DE. No warped rotors. I change out the fluid after every other event.
I look at it this way, if I was still running on stock brakes, I would have gone through at least 3-4 sets of rotors and probably two sets of calipers so the big reds have paid for themselves.
10-22-2002, 04:28 PM
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I'm with 51,
It sounds as though you're ready for a big brake upgrade. I also went to TT front and c2 Turbo rears, just changed the front Pagid orange pads after 28 track days, no fade. Best upgrade I've made to date. I have front brake ducts forcing air to the center of the rotors for additional cooling as well. Crescent City Porsche in New Orleans has pretty good prices on calipers and rotors, speak to John. FYI
My brake setup works very well, so well that I disconnected the brake booster.
BTW, you'll need to run 17" wheels to clear the big reds.
good luck !
It sounds as though you're ready for a big brake upgrade. I also went to TT front and c2 Turbo rears, just changed the front Pagid orange pads after 28 track days, no fade. Best upgrade I've made to date. I have front brake ducts forcing air to the center of the rotors for additional cooling as well. Crescent City Porsche in New Orleans has pretty good prices on calipers and rotors, speak to John. FYI
My brake setup works very well, so well that I disconnected the brake booster.
BTW, you'll need to run 17" wheels to clear the big reds.
good luck !
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10-22-2002, 05:59 PM
#8
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Have you tried or heard of anyone trying one of those systems that actually mists water onto the brakes or into the brake ducts to help cool the rotors? If you are racing it would be a shame to get bumped up a class due to larger brakes, if you are doing DE that is probably the easiest option.
10-22-2002, 06:09 PM
#9
Burning Brakes
Patrick,
You're probably not going to like this response, and forgive me if I'm making some presumptions. But, the problem sounds like you are not using your brakes properly - specifically you are overusing your brakes. This is a common track driver's problem. You see the stock Carrera brakes are used in Class F club racing cars and those racers record very fast laptimes yet they use the same brakes and they don't get overheated. If I am correct you should revisit some instructing on the track to see where you could make more efficient and less use of the brake pedal.
You're probably not going to like this response, and forgive me if I'm making some presumptions. But, the problem sounds like you are not using your brakes properly - specifically you are overusing your brakes. This is a common track driver's problem. You see the stock Carrera brakes are used in Class F club racing cars and those racers record very fast laptimes yet they use the same brakes and they don't get overheated. If I am correct you should revisit some instructing on the track to see where you could make more efficient and less use of the brake pedal.
10-22-2002, 08:55 PM
#10
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JC - any particular advice or ideas about how, specifically, one misuses the brakes to cause overheating? I'm having brake-fluid-boiling issues in my '86 Carrera now that I am turning faster lap times. Before I start down the long, expensive road of replacing brake parts, I'd like to make sure that I, as the driver, am not the primary cause of the issues.
Is this typically from braking too long and not hard enough (i.e. not threshold braking?) or from braking where one just should not be braking? I'm running very competitive lap times in PCA Time Trials, so I don't think I'm just riding the brakes around the track...
Advice, ideas, thoughts appreciated.
Thanks,
Dean
Is this typically from braking too long and not hard enough (i.e. not threshold braking?) or from braking where one just should not be braking? I'm running very competitive lap times in PCA Time Trials, so I don't think I'm just riding the brakes around the track...
Advice, ideas, thoughts appreciated.
Thanks,
Dean
10-22-2002, 09:24 PM
#11
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Howard and 51,
I have an '87 930. Where did you get your TT brake kits? My one concern is being locked into having to buy a rotor from one manufacturer at a hefty price if I buy from a vendor. My buddy has 13" rotors on his Mustang, but can only get them from "that one place". Will the TT kits and adapters allow you to use factory rotors? Are all kits equal?
I just killed a set of new front rotors in 300 track miles over two days. I have the front brake cooling kits with the ductwork going to the front air dam. Plenty of air going in, but I still cooked 'em. Of course my speeds have gone up (150mph) while my times have come down to the very low 1:40's at Road Atlanta. So maybe it's time to think about some Big Reds? TIA
Jim
I have an '87 930. Where did you get your TT brake kits? My one concern is being locked into having to buy a rotor from one manufacturer at a hefty price if I buy from a vendor. My buddy has 13" rotors on his Mustang, but can only get them from "that one place". Will the TT kits and adapters allow you to use factory rotors? Are all kits equal?
I just killed a set of new front rotors in 300 track miles over two days. I have the front brake cooling kits with the ductwork going to the front air dam. Plenty of air going in, but I still cooked 'em. Of course my speeds have gone up (150mph) while my times have come down to the very low 1:40's at Road Atlanta. So maybe it's time to think about some Big Reds? TIA
Jim
10-22-2002, 09:47 PM
#12
RL Technical Advisor
[quote]Originally posted by Patrick E:
<strong>I have an '87 Carrera with relatively stock brake components, although I have added an OG Racing cool brake kit, cryo front rotors, ss brake lines, Super Blue fluid and track pads (currently PF 97). In addition I have removed the dust covers, as the car is almost exclusively used on the track for DEs. My problem is that I frequently encounter brake problems resulting from overheating. I have warped rotors and calipers (yes, calipers!) and consistently cook the rubber boot on the caliper pistons, allowing fluid to leak out onto the pads and rotors. Over the past couple of years, I have replaced the master cylinder, brake lines, front calipers and rotors, and still encounter significant heating problems. The problems occur on all types of tracks, from CMP (which is brutal on brakes) to Roebling (which is not), and with different types of pads (I've used Hawkes, Pagid Blacks and now Performance Friction). I seem to experience normal wear on all eight pads and I don't think my braking technique is that dis-similar from others out there. Has anyone else encountered similar brake problems with a 911 on the track? Any suggestions? Constantly rebuilding/replacing brake components is getting expensive!</strong><hr></blockquote>
Hi Patrick:
I'm sorry to hear of your brake problems,....unfortunately, you are in good company. These cars are just too heavy for their heat dissipation capacity when used on the track.
The only effective solution is installing larger brakes that can dissipate that heat faster that you can generate it,.....
To this end, you have many options and I'd suggest two, based on our experiences:
1) For 15" or 16" wheels, you cannot beat the 930 rotors & calipers installed on all 4 corners. You will need the Turbo 23mm MC and that's included in a good brake kit.
2) If you wish to use 17" or 18" wheels, then the Big Red Twin-Turbo brakes will do the job very handily. You will need the 23mm MC here, too.
Part of the payback of using such large brakes on these lighter cars is the extended rotor and pad life you get with much reduced brake operating temperatures. I won't even touch on the confidence level you enjoy, so equipped,....
For Jim Bell,....Most of these kits do not use proprietary components and with rare exception, one would not confined to one supplier for replacement parts.
<strong>I have an '87 Carrera with relatively stock brake components, although I have added an OG Racing cool brake kit, cryo front rotors, ss brake lines, Super Blue fluid and track pads (currently PF 97). In addition I have removed the dust covers, as the car is almost exclusively used on the track for DEs. My problem is that I frequently encounter brake problems resulting from overheating. I have warped rotors and calipers (yes, calipers!) and consistently cook the rubber boot on the caliper pistons, allowing fluid to leak out onto the pads and rotors. Over the past couple of years, I have replaced the master cylinder, brake lines, front calipers and rotors, and still encounter significant heating problems. The problems occur on all types of tracks, from CMP (which is brutal on brakes) to Roebling (which is not), and with different types of pads (I've used Hawkes, Pagid Blacks and now Performance Friction). I seem to experience normal wear on all eight pads and I don't think my braking technique is that dis-similar from others out there. Has anyone else encountered similar brake problems with a 911 on the track? Any suggestions? Constantly rebuilding/replacing brake components is getting expensive!</strong><hr></blockquote>
Hi Patrick:
I'm sorry to hear of your brake problems,....unfortunately, you are in good company. These cars are just too heavy for their heat dissipation capacity when used on the track.
The only effective solution is installing larger brakes that can dissipate that heat faster that you can generate it,.....
To this end, you have many options and I'd suggest two, based on our experiences:
1) For 15" or 16" wheels, you cannot beat the 930 rotors & calipers installed on all 4 corners. You will need the Turbo 23mm MC and that's included in a good brake kit.
2) If you wish to use 17" or 18" wheels, then the Big Red Twin-Turbo brakes will do the job very handily. You will need the 23mm MC here, too.
Part of the payback of using such large brakes on these lighter cars is the extended rotor and pad life you get with much reduced brake operating temperatures. I won't even touch on the confidence level you enjoy, so equipped,....
For Jim Bell,....Most of these kits do not use proprietary components and with rare exception, one would not confined to one supplier for replacement parts.
10-23-2002, 12:27 AM
#13
Burning Brakes
Dean,
What exactly does it mean to use the brakes less? Here are some thoughts:
1. The brakes are not an on-off switch. Brake pressure is applied very quickly but not like a square wave.
2. Every corner does not require maximum brake pressure.
3. The most important part of the corner is the exit. Everything that occurs before the exit is done to maximize the exit speed.
4. You must be at full throttle at the apex or hopefully before. You must squeeze onto the throttle between the turn-in and the apex so that you are always at full throttle by the apex.
5. You must learn to trail brake for many corners that call for it. That means trailing off the brake pedal after the turn-in. The way you come off the brakes is very important. It must be a ramp off, again not a square wave.
I hope these tips help. It would be nice to have a ride with someone who has similar lap times in a similar stock Carrera but who does not have brake problems and see what they are doing.
What exactly does it mean to use the brakes less? Here are some thoughts:
1. The brakes are not an on-off switch. Brake pressure is applied very quickly but not like a square wave.
2. Every corner does not require maximum brake pressure.
3. The most important part of the corner is the exit. Everything that occurs before the exit is done to maximize the exit speed.
4. You must be at full throttle at the apex or hopefully before. You must squeeze onto the throttle between the turn-in and the apex so that you are always at full throttle by the apex.
5. You must learn to trail brake for many corners that call for it. That means trailing off the brake pedal after the turn-in. The way you come off the brakes is very important. It must be a ramp off, again not a square wave.
I hope these tips help. It would be nice to have a ride with someone who has similar lap times in a similar stock Carrera but who does not have brake problems and see what they are doing.
10-23-2002, 01:16 AM
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Jim,
I didn't buy a "kit", I pieced it together. Calipers from Crescent City Porsche, rotors from Vertex, the adapter brackets for the front from Wrightwood Racing ( Steve Weiner is a distributor) and I made the brackets for the rear and modified the calipers by milling the lobes off and drilling and taping 3 new mounting holes. It's a tight fit on the SC trailing arms. Your 930 will be a little easier to upgrade.
good luck !
I didn't buy a "kit", I pieced it together. Calipers from Crescent City Porsche, rotors from Vertex, the adapter brackets for the front from Wrightwood Racing ( Steve Weiner is a distributor) and I made the brackets for the rear and modified the calipers by milling the lobes off and drilling and taping 3 new mounting holes. It's a tight fit on the SC trailing arms. Your 930 will be a little easier to upgrade.
good luck !
10-23-2002, 04:00 AM
#15
The big leap to big reds or 930 brakes means a serious dollar commitment. Probably a minimum of $2500, multiply by 2.5X if 17" wheels are needed for add'l clearance.
You seem to have done all the necessary upgrades shy of bigger brakes. We've found that borderline brake fluid boiling may be minimized by using Ti Brake Shields. These insert between the pad and the caliper piston and effectively insulate the piston, seals and brake fluid from brake heat; but only up to a certain point. If you're creating so much rotor-warping heat, then these shields will do little to prevent that. Perhaps a look at a brake system upgrade or, as some suggest, your braking technique might be in order. As others have said, there are plenty of fast 911s using stock calipers/rotors. Maybe a different combination of driving technique and braking might save you some $$.
Sherwood Lee
<a href="http://members.rennlist.org/911pcars" target="_blank">http://members.rennlist.org/911pcars</a>
<a href="http://www.seinesystems.com" target="_blank">www.seinesystems.com</a>
You seem to have done all the necessary upgrades shy of bigger brakes. We've found that borderline brake fluid boiling may be minimized by using Ti Brake Shields. These insert between the pad and the caliper piston and effectively insulate the piston, seals and brake fluid from brake heat; but only up to a certain point. If you're creating so much rotor-warping heat, then these shields will do little to prevent that. Perhaps a look at a brake system upgrade or, as some suggest, your braking technique might be in order. As others have said, there are plenty of fast 911s using stock calipers/rotors. Maybe a different combination of driving technique and braking might save you some $$.
Sherwood Lee
<a href="http://members.rennlist.org/911pcars" target="_blank">http://members.rennlist.org/911pcars</a>
<a href="http://www.seinesystems.com" target="_blank">www.seinesystems.com</a>