Need new brakes for your family car? You can drive to the local auto parts store to pick them up and have them installed in just a couple of hours even if you want them to be upgraded to higher performance standards.
Want new brakes on your Sprint Cup car? Well, that might take a little longer.
Jim Kontje, motor sports director for NASCAR brake supplier Brembo North American, said it might take you a few months longer. Maybe six or even seven months longer, in fact.
Why so long? Even with many years of experience and knowledge in brake design and development, the engineers at Brembo have a multistep process to go through to develop a new braking system for a NASCAR race car. Brembo has working agreements with several Sprint Cup teams that serve as technical partners to share test data to accelerate the process but it can still take many months to get a new system to the prototype stage for actual testing.
Kontje said the latest problem Brembo was trying to solve for teams was cooling the front and rear brakes on the new car.
"Normally the emphasis is on cooling the front brakes but with the new car we are having issues with cooling the back brakes as well," Kontje said.
So if all the teams want more brake cooling in the front and the rear then how do you get there?
The process begins with Brembo developing a new caliper style through "finite element analysis," which is a process where a machine takes pictures of a new caliper design to identify any potential weak spot by creating a color pattern based on heat and cold. The hot areas are red and the cold areas are blue with incremental color gradations in between to show the engineers where there is good air flow and where it needs to be improved.
The "FEA" analysis process is repeated with refined caliper designs until the engineers are satisfied that they have achieved their goal of uniform cooling of the caliper.
When the caliper meets the company's preliminary expectations and passes the "FEA" it is then subjected to more sophisticated testing called "computational fluid dynamics," where the air flow can be simulated to match the varying air flows experienced at the track.
The teams have very intricate computer programs [called track mapping] that have been developed from their testing at the various tracks that allow them to duplicate every lap of a race for finite analysis. Using the "CFD" system they can vary the air flow to and over the brakes to re-create almost any actual or anticipated situation they see on the track.
Once all of the preliminary testing has been completed and the engineers are satisfied with the results they proceed to machine the final design of the caliper from aluminum so it can be tested on a brake dyno. We are getting closer here, folks!
The brake dyno simulates the actual operation under racing conditions by duplicating the entire front end of a Sprint Cup car so the engineers can flow air through the ducts just like they would experience at the track. This allows them to simulate following closely behind another car by limiting the amount of air flow reaching the brakes. Following close behind another car is much more stressful on the braking system than when the car is in clean air that can flow more easily to the brakes.
Kontje explained that they use the Martinsville simulation on the dyno because it is the hardest on the brakes with hard braking pressure being applied every eight seconds for 1,000 repetitions. Five hundred laps times two braking corners equals 1,000 applications per race. Temperatures at Martinsville can reach above 1,200 degrees per braking application with just eight seconds of time for the system to cool off before the next corner and another application.
So now we have a finished aluminum caliper ready to race, right? No. Now we start the durability testing of the aluminum caliper to make sure it will hold up under the stresses experienced during a race. The prior testing and development was concerned with cooling the caliper.
Aluminum can weaken from repeated exposure to heat so durability must be proven before the caliper is ready for production. Brembo puts the caliper through 500,000 test cycles of applying pressure to simulate the braking application on the track. This is done in-house on a special machine.
Once the prototype has passed the in-house durability test it is ready for on-track testing and final approval by the manufacturer and the teams to confirm that it will perform as expected. Then, and only then, is it cleared for actual production.
Kontje said as much as six months time has elapsed from starting the first step in the process to the final OK for production. Whew, we are finally there! Uh, what about the brake discs and the pads, Jim?
"The brake discs and pads are developed in a similar way through the same process on a parallel path to the caliper," Kontje said. "Throughout the process we are cross checking and confirming the compatibility of all of the components so that, in the end, we have a product that will do the job as designed."
Sounds a little more complicated than running down to the local auto parts store doesn't it! But wait, we're not done yet.
Let's talk about rotors or discs as Kontje prefers to call them. Discs, calipers and pads come in a variety of designs. The calipers need to be cooled to avoid boiling the brake fluid from the radiant heat generated by the pads and disc that could cause brake fade or failure if air should get into the closed system. The discs need to be cooled rapidly on a short track to reduce the radiant heat exposure to the caliper and to avoid brake fade and the potential smearing of the pad material onto the disc surface, which would also reduce the brakes effectiveness.
The discs are not solid like on your passenger car but have a series of vents or veins separating the two surfaces where the pads make contact. These cooling blades, as Kontje called them, are designed to pull air into the middle of the disc to help cool it rapidly and evenly.
Think of a waterwheel working in reverse. Instead of the water flowing over the wheel to turn it, the disc rotates on the spindle and the angled slots grab air and pull it into the disc. The brakes need as much air as possible to flow through and around the disc and pads to help cool them to maintain their efficiency.
The brake pads are designed to create as much friction as possible for them to be effective. The anticipated temperatures that will be created by the braking on each particular track influences the type of disc and the composition of the pads so they will work in harmony and be consistent throughout the race. That is one reason that brakes are often made specifically for a particular driver and his style of braking.
Some drivers use more brakes than others so that has to be factored into the equation of how much heat will be generated. It has become a very exacting science just like the other areas of the new car. The areas to be exploited to gain an advantage have narrowed considerably so all efforts are made to maximize the benefits to be gained no matter how limited they might be.
One side effect of all that development effort is that teams no longer run brake fluid recirculating systems to keep the brake fluid from boiling in the caliper. But all modifications must be submitted to NASCAR for its review and approval.
While short tracks like Martinsville are extremely tough on brakes, it is Watkins Glen that gets Kontje's vote as the toughest on brakes. Brake temperature "spikes" can reach as high as 1,400 to 1,500 degrees at the road course but have longer periods of time to cool down before the next turn. That creates a bigger swing in temperatures versus the more sustained temperatures on the short tracks such as Martinsville.
This creates a different set of problems for the brake gurus because wide temperature variances can lead to cracking of the discs.
Or it can effect the performance of the pads if they cool off too much. The pads are designed to operate efficiently in a specified temperature range. If the pads cool off or heat up too much then their performance could be diminished.
Although they have cured the problem in more recent years, brake discs have been known to literally explode because of the wide temperature swings that can occur on road courses.
Kontje gave examples of putting an ice cube into a glass of warm water and watching it crack because of the temperature difference or placing a hot brake disc into a cool bucket of water and making the water boil almost instantly to illustrate his point of how wide the temperature swings can be.
While the short tracks and road courses utilize the biggest braking systems, tracks such as Talladega run the lightest systems because drivers use their brakes only when they are pitting or perhaps trail braking to maintain a distance from another car. Or, of course, trying to avoid "The Big One."
Running smaller discs and pads to reduce drag creates the problem of the driver having to jam the brakes on harder to stop. That is why you sometimes see them smoking their tires when they are trying to get slowed down coming into the pits. Kontje explained that the Talladega brake setups would probably not last 10 laps at Martinsville because they are so much smaller.
We've designed and built brakes to exact specifications for a particular track and a certain driver so our work should be done -- but it isn't. We have one more trick up our sleeve. It is called the brake bias valve. It's a handy little gadget that allows the driver to move brake application pressures from front to rear or vice versa to help balance a less than perfectly handling car. It is a temporary fix until they can get to the next pit stop but it is the only adjustment the driver has available to him during the race.
Teams will generally set up their pressures to be 600 PSI to the front brakes and 400 PSI to the rear brakes, which is a neutral or balanced setup, Kontje said. If the car is too tight then the driver can adjust his brake bias valve by two or three turns to move pressure to the rear and help loosen it up. Or he can tighten it up by moving pressure to the front. It is a temporary fix until the team can make proper adjustments on a pit stop, but it can help a driver stay competitive until that happens.
Kontje noted that the drivers are constantly playing with the bias valve at Martinsville trying to get a better balance on a very difficult track to achieve a good handling package.
Bill Borden is a former championship winning crew chief who operated David Pearson's Racing School for many years.