BRAKES
By Gary Phillis April 2004
Background: Lap times from 70-90 seconds, 4 heavy braking zones per lap, 5300ft. elevation with low humidity = no time or air to cool brakes = Trouble!
Racing is very hard on brakes. At all Colorado racetracks there is no high-density humid air to carry away the heat. Brakes work by changing your forward motion into heat. To keep the brakes working that heat needs to be dissipated quickly. In Colorado that is hard to do. Most of us do not have the option of the large European Racing Trucks of carrying 100 gallons of water to cool the brakes. (Maybe the Hotruck??)
What can you do?
- Get real racing brake pads
- Get high temperature brake fluid
- Add ducting to get lots of air to the front brakes
Real racing brake pads are a must at any time trials event. Street pads will overheat and probably go away on your second lap right when you want to brake for turn 1. You will at that point get a rapid education on the utility of the escape road. Check out the cherry red front rotors of this STS Integra for an example (and this was a cold November day):
At the race track you will need pads that can handle at least 1000 deg. F temperatures. See above picture.
From a welding handbook:
COLOR |
TEMP °F |
|
Faint Red |
900 |
|
Blood Red |
1050 |
|
Dark Cherry Red |
1075 |
|
Medium Cherry Red |
1250 |
|
Cherry Red |
1375 |
|
Bright Red |
1550 |
I think you get the point that brakes get hot at this track! At these temperatures your stock pads will literally melt. Especially after a 30 minute lapping session.
Lots of Solo2 people like Carbotech pads, and they are now making some high temp pads: http://www.carbotecheng.com/
Cobalt Friction also makes both endurance and road racing pads designed to last a long time at high temperature. http://www.cobaltfriction.com/
Porterfield sells a large variety of pads and will make pads for any vehicle. Andy Porterfield is a long time SCCA Guy and current BOD member. Note the R4S will not last at Second Creek, but the R4 pad is used by a lot of Club Racing folks in the region. http://www.porterfield-brakes.com/
Real racing brake pads are not cheap, but then neither is your car. Most of the regular Time Trials folks have a set of real race pads that are switched in just before the event, and then go back to street pads for everyday use.
Most modern cars have a thin stainless steel plate between the brake pads and the caliper. This is a heat shield that helps block the transfer of heat from the hot brake pads to the caliper piston and the brake fluid beyond. If you don’t have such a shield, make one. Some folks use two of them to make a better thermal barrier. Stainless steel is a good thermal barrier.
HIGH TEMPERATURE BRAKE FLUID
Ok now you’you've got real racing pads that can handle higher temperatures and you boil your stock brake fluid. What to do? Try one of the following high temp brake fluids. The Dry and Wet boiling points indicate whether there is water in the brake fluid or not. Brake fluid absorbs water. This lowers the boiling point as indicated in the chart. So the Dry boiling point is just before you open the brake fluid container. When you open the container the brake fluid starts absorbing water from the air. Luckily in Colorado we have fairly dry air. But brake fluid water absorption means that you should bleed you brakes just before you go to the track. Watch the Club Racers bleed their brakes the morning of the event, and after qualifying just before the race. They want that max temp Dry boiling point.
HIGH TEMP BRAKE FLUID COMPARISON
| Brand | Castrol SRF | ATE Super Blue | AP-600 | AP-550 | Wilwood EXP | Wildwood 570 | Performance Friction Z-Rated | Ford Heavy Duty | Castrol LMA | Motul 600 |
| DOT Rating | 4 | 4 | 3 | 3 | 3 | 3 | 3 | 4 | 4 | |
| Wet Boiling Point | 518° | 382° | 410° | 284° | 417° | 284° | 284° | 284° | 311° | 421° |
| Dry Boiling Point | 590° | 536° | 590° | 550° | 600° | 570° | 550° | 550° | 446° | 600° |
| Compatable with other fluids? | Yes | Yes | NO | Yes | Yes | Yes | Yes | Yes | ||
| Package | 33.8 oz | 1 liter | 16.9 oz | 16.9 oz | 12 oz bottle $16.95 | 12.0 oz | 16.0 oz | 16.0 oz | 12.0 oz | $12.95 per 1/2 liter |
THE IMPORTANCE OF AIR
You've now got real racing pads and high temp brake fluid and you still boil you brake fluid and the pads get mushy – what to do? Get more air!
Brakes work by transferring heat energy to the surrounding air. If there is not enough air to carry the heat away, you lose your brakes. So we need to make sure we get a lot of air across the rotors and calipers and keep them cool(er). Especially with our thin dry air in Colorado
Stock and Street Prepared cars have metal backing plates in back of the brake disk that is there to prevent water from splashing on the brakes. This splash shield also keeps air from cooling the brakes. Bend that sucker out of the way! You’ve got to keep it on the car by class rules but move it so that air can get to the brakes.
Run a large diameter cooling duct and hose from the front of the car to put a lot of air across the brakes. This is not easy as you’ve got to keep the hose from dragging on the ground and getting tangled up in the suspension and hit by the wheel and tire. But it can be done, take a look at all the brake ducts on a NASCAR car setup for a road course. You can do it to and you get real street cred as well as styling points. Do take the ducting off for the winter, as they will pack with snow.
Another viewpoint: http://www.grmotorsports.com/brakes.html
If after you have done all of the above and you still cook your brakes – what to do? Well um, brake less. Easy to say and hard to do. With more experience you will find you are using less and less brakes and carrying more speed through the corners. Learn to be gentle with your brakes and they will last (a little) longer.
