Brake Overheating
10-23-2002, 10:13 AM
#16
Rennlist Member
Jim Bell:
The shop that works on my car got my brakes from a place in CA. I think the name was RC something?. The kit uses Porsche factory rotors, not aftermarket, so you can get the rotors from anyone who sells factory parts. I have heard some stories of kits that use aftermarket rotors. I forgot to mention that I also installed a 23mm master cylinder.
Like I said, the initial costs were more, but over the long haul, the upgrade has paid for itself. For me, reducing the yearly operating costs was worth the bump in class.
JC:
The F class guys in Carreras (and C2s for that matter) that I know, do go through rotors. It all comes back to heat sink capability. The stock rotors just aren't big enough to dissipate heat.
The shop that works on my car got my brakes from a place in CA. I think the name was RC something?. The kit uses Porsche factory rotors, not aftermarket, so you can get the rotors from anyone who sells factory parts. I have heard some stories of kits that use aftermarket rotors. I forgot to mention that I also installed a 23mm master cylinder.
Like I said, the initial costs were more, but over the long haul, the upgrade has paid for itself. For me, reducing the yearly operating costs was worth the bump in class.
JC:
The F class guys in Carreras (and C2s for that matter) that I know, do go through rotors. It all comes back to heat sink capability. The stock rotors just aren't big enough to dissipate heat.
10-23-2002, 11:20 AM
#17
Burning Brakes
[quote]Originally posted by Carrera51:
<strong>
The F class guys in Carreras (and C2s for that matter) that I know, do go through rotors. It all comes back to heat sink capability. The stock rotors just aren't big enough to dissipate heat.</strong><hr></blockquote>
Absolutely! You will go through rotors but they are pretty cheap. Make sure all of the brake system components are in top shape. My point is that the stock components are adequate for racing and an upgrade is not strictly necessary to achieve the very fastest laptimes in these cars.
<strong>
The F class guys in Carreras (and C2s for that matter) that I know, do go through rotors. It all comes back to heat sink capability. The stock rotors just aren't big enough to dissipate heat.</strong><hr></blockquote>
Absolutely! You will go through rotors but they are pretty cheap. Make sure all of the brake system components are in top shape. My point is that the stock components are adequate for racing and an upgrade is not strictly necessary to achieve the very fastest laptimes in these cars.
10-23-2002, 11:27 AM
#18
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JC,
Thanks for the tips. I've got a track day coming up at Laguna Seca in a couple weeks, and I'll work on my braking! I'm also going back to Thunderhill, the "scene of the crime" where my brakes have overheated in the past, and will see if I can't improve...
Thanks again,
Dean
Thanks for the tips. I've got a track day coming up at Laguna Seca in a couple weeks, and I'll work on my braking! I'm also going back to Thunderhill, the "scene of the crime" where my brakes have overheated in the past, and will see if I can't improve...
Thanks again,
Dean
10-23-2002, 12:18 PM
#19
PatrickE:
One item not mentioned anywhere ( before you take the big plunge into larger brakes)..is the brake proportioning valve.
The 84-89 Carrera'a have a brake proportioning valve on the trunk floor next to the smuggler's box. Early cars use a 5/33 stamped unit ( size 5...brake power cut in half once 33 bar pressure is reached). you may be severely over-taxing the fronts, and may want to try for more rear-bias. Check your car now...are the front brakes particulary dirty and the rears fairly clean? That might be a hint. Go for a unit that has a higher pressure thresh-hold ( 5/50 ?), or like the cup cars...you may want to remove it entirely...but that may be TOO SEVERE...so be careful with this approach and step-up slowly.
As to technique...a fast, hard jab at the last moment is much better than gradually easing on more pressure toward the end of your braking zone. Upsets the car less, too, as you hit the apex ( less chance of nose "popping up" by instead braking hard sooner, and easing up before turn-in). Make sense?
Also, I never use the brakes on my last cool-down lap into the pits...even a quick jab on the brakes in pit lane can wreak havoc. I idle around pit/ garage lane and stop by pushing down on the clutch, turning the engine off..and as you coast to your final stopping point...simply re-engage the clutch slowly to stop the car. Brakes will get a LOT less heat soak !!
With doing all this, I haven't had a problem running DE's with my 85 Carrera at Watkins Glen.
--Wil Ferch
One item not mentioned anywhere ( before you take the big plunge into larger brakes)..is the brake proportioning valve.
The 84-89 Carrera'a have a brake proportioning valve on the trunk floor next to the smuggler's box. Early cars use a 5/33 stamped unit ( size 5...brake power cut in half once 33 bar pressure is reached). you may be severely over-taxing the fronts, and may want to try for more rear-bias. Check your car now...are the front brakes particulary dirty and the rears fairly clean? That might be a hint. Go for a unit that has a higher pressure thresh-hold ( 5/50 ?), or like the cup cars...you may want to remove it entirely...but that may be TOO SEVERE...so be careful with this approach and step-up slowly.
As to technique...a fast, hard jab at the last moment is much better than gradually easing on more pressure toward the end of your braking zone. Upsets the car less, too, as you hit the apex ( less chance of nose "popping up" by instead braking hard sooner, and easing up before turn-in). Make sense?
Also, I never use the brakes on my last cool-down lap into the pits...even a quick jab on the brakes in pit lane can wreak havoc. I idle around pit/ garage lane and stop by pushing down on the clutch, turning the engine off..and as you coast to your final stopping point...simply re-engage the clutch slowly to stop the car. Brakes will get a LOT less heat soak !!
With doing all this, I haven't had a problem running DE's with my 85 Carrera at Watkins Glen.
--Wil Ferch
10-23-2002, 12:22 PM
#20
Race Director
JC,
Questions on Brake usage. I have 944 2450lbs & 150hp with stock brakes and cooling duct. No brake problems after cooling ducts were added.
With my car my approach to braking is not to "over-brake" the car. What mean is to no slow the car too much since with low-hp momentum is everything.
I usally try to roll onto the brakes frimly but smoothly rather than "stand-on-them" in any corner. The exception is pass attempts or emegenency manuevers. I feel that the rapid, but firm roll on of brake makes the car more stable under braking and prevents me from "over-braking" I also tend to roll off the brakes and often am turing the wheel while doing this so I am effectively trail braking.
Does this sould like the propper view of braking for good part life and good lap times?
Thanks
Questions on Brake usage. I have 944 2450lbs & 150hp with stock brakes and cooling duct. No brake problems after cooling ducts were added.
With my car my approach to braking is not to "over-brake" the car. What mean is to no slow the car too much since with low-hp momentum is everything.
I usally try to roll onto the brakes frimly but smoothly rather than "stand-on-them" in any corner. The exception is pass attempts or emegenency manuevers. I feel that the rapid, but firm roll on of brake makes the car more stable under braking and prevents me from "over-braking" I also tend to roll off the brakes and often am turing the wheel while doing this so I am effectively trail braking.
Does this sould like the propper view of braking for good part life and good lap times?
Thanks
10-23-2002, 01:05 PM
#21
Burning Brakes
[quote]Originally posted by M758:
<strong>Questions on Brake usage. I have 944 2450lbs & 150hp with stock brakes and cooling duct. No brake problems after cooling ducts were added.
With my car my approach to braking is not to "over-brake" the car. What mean is to no slow the car too much since with low-hp momentum is everything.
I usally try to roll onto the brakes frimly but smoothly rather than "stand-on-them" in any corner. The exception is pass attempts or emegenency manuevers. I feel that the rapid, but firm roll on of brake makes the car more stable under braking and prevents me from "over-braking" I also tend to roll off the brakes and often am turing the wheel while doing this so I am effectively trail braking.
Does this sould like the propper view of braking for good part life and good lap times?
</strong><hr></blockquote>
You technique sounds great and if it works for you keep it up! Your goal is the fastest laptimes you can attain. If you can manage your brakes and achieve this then you are winning.
I don't race a non-turbo 944, but those that do tell me that you can drive around many tracks with your foot on the floor almost the whole time and use the brakes only a few times per lap - so brakes should not overheat in this scenario. Of course this is an oversimplification but my feeling is that the 944 with competition tires has to be finessed with heavy right foot and very little bleeding off of speed with the brake pedal to get fast laps as you said.
<strong>Questions on Brake usage. I have 944 2450lbs & 150hp with stock brakes and cooling duct. No brake problems after cooling ducts were added.
With my car my approach to braking is not to "over-brake" the car. What mean is to no slow the car too much since with low-hp momentum is everything.
I usally try to roll onto the brakes frimly but smoothly rather than "stand-on-them" in any corner. The exception is pass attempts or emegenency manuevers. I feel that the rapid, but firm roll on of brake makes the car more stable under braking and prevents me from "over-braking" I also tend to roll off the brakes and often am turing the wheel while doing this so I am effectively trail braking.
Does this sould like the propper view of braking for good part life and good lap times?
</strong><hr></blockquote>
You technique sounds great and if it works for you keep it up! Your goal is the fastest laptimes you can attain. If you can manage your brakes and achieve this then you are winning.
I don't race a non-turbo 944, but those that do tell me that you can drive around many tracks with your foot on the floor almost the whole time and use the brakes only a few times per lap - so brakes should not overheat in this scenario. Of course this is an oversimplification but my feeling is that the 944 with competition tires has to be finessed with heavy right foot and very little bleeding off of speed with the brake pedal to get fast laps as you said.
10-23-2002, 04:50 PM
#22
The 84-89 Carrera used the p/v because of a mismatch in f/r piston sizes. As long as the correct piston sizes are used f/r there is no need for the p/v. Later cars have correct bias but use a p/v because ABS covers a lot of sins and so that the rears are used more in non aggressive braking situations, this evens the wear in f/r pads that is a concern to many owners.
As others have pointed out you need a larger heat sink(rotor)There are 2 larger sizes generally available for the front of your car
In the back use the 930 309x28 rotor. If the 993/S4 or Big Red is in the front then use a 964T rear caliper for best bias or a modified 993 C4S rear caliper for a little more front bias. If 930 front caliper is used then best bias is w/ a 930 rear caliper.
None of the above combos need a p/v though some people do like more front bias and do experiment w/ them. All of them should be used w/ a 930 23mm m/c. (the 930 calipers can be used w/ your stock 20.6mm m/c but its not optimal).
As others have pointed out you need a larger heat sink(rotor)There are 2 larger sizes generally available for the front of your car
- 304x32 930 spec
- 322x32 993tt spec
In the back use the 930 309x28 rotor. If the 993/S4 or Big Red is in the front then use a 964T rear caliper for best bias or a modified 993 C4S rear caliper for a little more front bias. If 930 front caliper is used then best bias is w/ a 930 rear caliper.
None of the above combos need a p/v though some people do like more front bias and do experiment w/ them. All of them should be used w/ a 930 23mm m/c. (the 930 calipers can be used w/ your stock 20.6mm m/c but its not optimal).
10-23-2002, 05:58 PM
#23
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Nice thread here. I've found lately that when I try to carry my speeds deeper into corners, and brake harder, I don't give my car time to settle sufficiently to get a good line through the turn, and my lap times suffer. You think you're going faster, but you end up going slower. Nothing like a hot lap system to tell you when you're doing the wrong thing...and wasting expensive brake pads. (I recommend Pagid Blacks)
