Speed Secrets: Brakes - A Recipe For Disaster!
By Ross Bentley
March 11, 2014
As they learn performance driving techniques, most drivers demonstrate the same pattern when it comes to using the brakes; beginners either have no idea how effective their brakes are at shedding speed or they immediately abuse them. Then, the timid ones flop to the other side by extreme braking by the end of their first day. All beginners, at some point, typically overuse this pedal.
At the same time these beginners are gaining skills in all areas so they will advance after a few events to become some of the more difficult-to-coach drivers: "the intermediates."
Intermediate skill level drivers have brake problems, too. One reason is that they are working on honing the proper use of the brakes (which takes a dedicated and skilled coach); another is that many intermediates have the "I got this" mentality... saying something like, "yeah, I'm pretty experienced, I just bought this new limited edition double-throw-down carbon black Merade, and have done a couple of years of DE events and..."
So the bad habit of brake system overuse continues. Here's the #1 reason for brake problems on track: Being on the track in the first place!
When you mix the following on a racetrack:
- 4,000 pounds
- 400 horsepower
- Five heavy braking zones per lap
- 120 mph - 45 mph in four seconds
- Three mile long lap
- 20 minute session length
- Six laps per session
THAT'S A LOT OF ENERGY; it makes a mess of stock brake pads, rotors, and your wallet!
Here are some eye-opening numbers:
At a deceleration rate of about 0.90G, one braking event equates to:
- Over 2,300 BTU of energy (then unit conversion to put this in perspective)
- 825 horsepower PER BRAKE ZONE!
Bet that number gets your attention.
Perhaps it's easier to understand how intermediate level performance drivers - using their brakes harder now, with more experience - suffer brake system issues with some frequency.
This amount of kinetic energy must first be absorbed by your cast iron (or carbon ceramic, if you're an exotic car owner) front brake rotors (70% of braking energy is managed by front brakes), raising their temperature during the first stop from ambient to about 800°F.
By the second lap you're flirting with 1,000°F; two laps later sparks of molten iron are tossed onto the inside of your wheels. The kinetic energy is transformed to heat. But the unmodified rotor cannot shed the heat quickly enough and some of that heat is transferred through the brake pad (ostensibly an insulator) to caliper pistons, piston seals and brake fluid, raising fluid temperature to over 500°F, beyond the dry boiling point of generic brake fluid.
Say hello to Señor Spongy Brake Pedal!
What can you do to prevent, reduce severity, or delay this from happening?
- Fresh high-quality fluid with a dry boiling point greater than 500°F (DOT 3 or DOT 4 are meaningless FMVSS (Federal Motor Vehicle Safety Standard) minimum specification standards. So get the manufacturerʻs specs!
- Thick brake pads in a compound formulated to perform at 1,000°F (not combo street-track pad formulations).
- Heat-insulating titanium brake pad shims (titanium is a thermal insulator).
- Duct air directly to the center of vented front brake rotors.
- Add low volume flow water aspirator to brake air-duct.
Okay, so items one through three are easy for anyone to perform and add to their preparation list; four and five are not so easy. But it's the only way a production-based or tube-frame race car can survive more than just a few laps. Brake air-ducting kits are becoming more common as manufacturers and the aftermarket realize their customers participate in performance driving events.
What else can you do?
Learn proper braking technique, especially the most difficult to perfect: brake release.
Ultimately, the current trend for cars to get heavier each year is working against you. So if you're new-car shopping, spring for the brake upgrade; the more massive the front rotors the better off you'll be. Try to resist buying anything approaching 4,000 lbs curb weight as a track car. Instead shop online for a nice used car (from twenty years ago) that scales close to 3,000 lbs.
And go for the non-fat caffè latte vs. the white chocolate venti mocha. It does a body good!
- Rob Schermerhorn