(Originally published June 22, 2007)
Back in the early days of NASCAR, cars were basically street-legal vehicles that were driven to the track, raced and then driven back home again. All of the components were virtually "street" stock. Buddy Baker used to tell a story about how, when he was a very young boy, his father, Buck Baker, would race on the old beach course in Daytona.
Buck would load up his family in the car he planned to race and bring them along for a short vacation at the beach. Buddy would crawl up on the package shelf below the rear window to sleep and stay cool during the trips to and from Daytona Beach. There were times that their vacations would be extended for a few days if Buck wrecked the family transportation during the old beach race. Most of the time Buck would have to clean the sand out of the car's old drum brake system to make sure they were working properly before heading back to North Carolina. But, according to Buddy, no matter if the vacation was short or extended, there would always be enough sand left inside the car to refill his sand box when they got home.
Buddy told that story more than 25 years ago in the early 1980s as an example of just how much more sophisticated NASCAR racing had become from Buck's era to Buddy's era. They were using modified aircraft braking systems during Buddy's era versus Buck's old drum brakes. However, if you compared Buddy's race car brake systems to the brake systems on today's race cars you would see an even greater disparity in the technology.
To understand the importance of brakes on today's race cars you must understand that energy can be transferred. The same amount of energy (horsepower) that is required to propel a race car (mass) forward is needed to stop it -- Physics 101. Energy can be transformed into heat and dissipated. The glowing red rotors you see on a race car demonstrate the conversion of the moving energy mass into heat as the brakes are applied and the brake pads rub against the rotor to create friction to slow down the race car.
If you ever get to watch a live Space Shuttle launch and feel the awesome power of the rockets shaking the ground as they lift it into orbit and then remember afterward that all of that "thrust" energy has to be dissipated before it can land, then you understand the important role brakes play on a race car. All of the energy that was generated by the Shuttle's launch is still propelling it in its orbit around the Earth. Shuttles don't have brakes so the NASA engineers have to convert all of that moving energy into heat through the friction of the Shuttle's ceramic heat shield rubbing against the Earth's atmosphere as it re-enters from its orbit in a controlled descent.
While building race cars is not rocket science it is becoming more sophisticated each year. Millions upon millions of dollars are spent developing stronger and more powerful engines to make the cars go faster. But every gain in horsepower means that better brakes are needed to slow all those "ponies" down and stop 'em.
A race car's brakes serve multiple purposes and have become an important part of the setup equation. Today's race cars have brake bias valves that allow the driver to adjust the amount of fluid pressure that is applied between the front and rear wheels so he can change the car's handling performance. Unlike your passenger car's more "balanced" braking system, race cars need more front brake pressure to help create more "dive" in the front end and to help them slow down faster. "Dive" refers to how much the front end drops when the driver lifts off of the accelerator and applies the brakes. Creating "dive" helps the car turn into the corner more easily as the driver turns the steering wheel and applies the brakes. Race cars are designed to turn left so, depending upon the spring rating and the front end geometry, the driver can literally steer the car into the corner by how hard he applies the brakes.
When a driver races on a short track he tries to make a circle out of an oval. That is why you see the cars running at the bottom of the track in the center (or apex) of the corners and up near the outside walls in the straights. He is making a "geometric apex" so he can make a smoother and more stable lap than if he tries to square off the corners.
That is one reason that Martinsville is much harder on brakes than Bristol or Richmond even though those tracks have much higher racing speeds. Martinsville is atypical of most short tracks because it has very long straights and very tight corners which make it impossible for the driver to make a circle out of an oval. The longer straights mean the driver carries more speed into the corners and therefore needs more braking application to slow the car down more quickly to make the transition into and through Martinsville's tighter corners. If the driver doesn't use enough brake application then the car will want to wash out to the wall as centrifugal force carries it out there. If he inputs too much brake application then the rear end will want to come around and spin the car out. It is a very delicate move and it is why they call it the "pucker point" or "puckering moment". The driver has to have complete confidence that when he puts his foot on the brake pedal the car will do what he expects it to do. Today, the teams can have rotors and pads specifically designed for their driver's style of braking to achieve a smoother entry into the corners.
Brakes play a much more important role for the driver on short tracks and road courses than they do on superspeedways because of the difference in the driving style that is required to compete on them. Braking is involved during every lap made on a short track or road course but the driver will seldom touch his brakes on a superspeedway except during a pit stop or possibly trail braking going into the corner to help set the front end."Trail braking" means the driver applies a gentle and continuous pressure to the pedal versus pushing down hard on it. In fact, before drivers qualify on the superspeedways, the crews will release the pressure of the pads rubbing against the rotors to reduce the little bit of drag caused by the friction of them rubbing together just to gain a valuable 10th-of-a-second or so on the stopwatch.
Buddy Baker was proud of the fact his race car had the technology of aircraft style brakes back in the early '80s. However, today's airplane pilot would be proud to have the technology of the current NASCAR Nextel Cup style brakes on his airplane.
Just where do you acquire better brakes than you can get on an airplane? From brake companies that specialize in manufacturing advanced technology race car braking systems. The leader in brake technology for NASCAR is Brembo North American, which is owned by an Italian company that also supplies brake parts for Formula One cars.
"Brakes have become a vital and important part of today's race car setups and must work in harmony with them," said Jeff Leonard, the NASCAR program manager for Brembo North American. The team engineers and setup specialists take the information they have learned from their previous races and testing at a specific track along with the data provided by the Brembo engineers (or a Brembo competitor such as AP) to decide what type of rotors and brake pads they want to run based on the track, their selected suspension setup and their driver's style of driving.
Just how critical is the driver component of the setup formula? Take the four Hendrick teams for example: You would assume that the cars would be the same or, at most, moderately different in their setups. However you would be wrong. Jeff Gordon and Jimmie Johnson probably have the most similar driving styles so their cars would be the closest in set ups and brake systems, etc.. But, in fact, Johnson "borrowed" Gordon's complete setup at Martinsville this spring when his setup did not work satisfactorily for him or the stopwatch. Jimmie graciously showed his appreciation to Jeff by beating him in a frantic duel between the two of them over the last few laps. And, Gordon did not appear to be very pleased with Johnson's way of saying thanks.
Johnson's and Gordon's current teammate Kyle Bush would require a completely different setup and braking system because of his hard charging and go-for-broke style of driving while their fourth teammate Casey Mears falls somewhere in between. The four cars -- out of the same racing group -- could be running very different brake packages at the same race track to accommodate their drivers and their selected setup packages.
So just how do brakes work anyway? As stated earlier, they work to convert moving energy into heat through the creation of friction caused by the pads rubbing against the rotors to slow down the car or stop it. The bigger the rotor the more heat it can absorb and therefore transform energy to a slowed or stopped race car more quickly.
Oh, if it were only that simple. The design goals are for the brakes to operate in an "average" heat range of 500 to 700 degrees. Around 500 for the back brakes and 600 to 700 for the front brakes. However, tracks like Martinsville and Watkins Glen can have heat spikes that go up as high as 1,400 to 1,600 degrees. To put that in perspective for you, I worked at the open hearth blast furnaces in a steel mill in the summer when I was going through college. The furnaces operated at temperatures in the 2,000 to 2,400 degree range to melt iron ore and make steel. There is only a few hundred degrees of difference between a race car's glowing rotors and flowing molten steel.
The continual heating and cooling of the brake rotors and pads during a race must be controlled or it can create problems for the teams. The brake gurus develop various combinations of friction materials for the pads (primarily carbon metallic based compounds) that are designed for each individual track to achieve the desired heat range for that track. If the pads get too hot during usage then the brake rotors can experience what is known as "smear" where the pads literally begin to melt onto the rotors at the higher temperatures. This can cause a glazing of the pads and rotors, basically rendering the brakes useless. If the brakes operate at too cool a temperature then they may "grind" and wear too quickly or unevenly. The primary goal is to have the pads wear off gradually and evenly and to keep the temperature ranges within desired tolerances so the brakes don't get too hot (but hot enough) or heat up or cool off too quickly which can cause damage to the system by cracking the rotors. A second goal is to match the braking power with the driver's style of application to avoid too much or not enough "dive" when going into the corner as stated earlier.
Also remember that everything done to a race car creates a compromise somewhere. If you make the brake rotors bigger to absorb more heat then you are adding unsprung and rotating weight. It requires more energy to move an unsprung or rotating mass forward so you are giving up something in one area to gain in another. So bigger is not always better. The teams weigh the gains against the losses in their particular situation and make their decisions accordingly. Some may accept the added weight penalty for a gain to their chosen setup and for their driver. Testing tells them which one is better.
OK, we've done our research and analysis, consulted with the brake gurus and determined which size and style of rotor (mass and number of veins) dissipates the heat the best for the track we are setting up to race on and which brake pad is going to wear the best to create the desired friction/heat level that we want. And we've selected the caliper style we need to gain the best pressure application for the driver and the most even pad wear (four piston or six piston) as well. We then install our selected brake system on the car and fill it with fresh, anti-boiling brake fluid that is good for temperatures up to 600 degrees. Even so, we will only run it for one race before we flush the system and refill it. That's lot of work just to counteract all that horsepower we spent millions to produce but, hey, that's racing. It is loaded with contradictions.
Today, just like 6-foot-5 Buddy Baker doesn't stand a chance of fitting into that rear package shelf of Buck's old Oldsmobile, Buck's brakes (sand and all) wouldn't stand a chance of lasting more than a few laps in today's competitive racing environment. Yes, Buddy, as that old Olds commercial says: "This isn't your father's Oldsmobile." In fact it isn't your old Oldsmobile either, Buddy! Nope, this baby is an entirely different kind of rocket.
Bill Borden is a former championship winning crew chief who operated David Pearson's Racing School for many years.