Stopping on a dime
By Michael Guerrero, Stock Car Racing Magazine
September 21, 2001
3:01 PM EDT (1901 GMT)
Winston Cup racing is usually wide-open, fender-to-fender racing action, but occasionally brakes come into play.
At some of the larger tracks (Daytona and Talladega) drivers only touch the brakes to slow down to enter pit road or avoid an accident. At short tracks like Martinsville, brakes are an essential element of success.
To learn more about the types of braking systems used in Winston Cup, Stock Car Racing went to Jimmy Elledge, crew chief of the No.55 Square D Chevrolet driven by Bobby Hamilton.
The main difference in the brakes between superspeedway cars and short-track cars is the size of the caliper and rotor, and the thickness and compound of the brake pads.
For Daytona, the calipers are relatively small, but at Martinsville the calipers are huge by comparison. On the big tracks teams use four-piston calipers, but on the short tracks and road courses they use a six-piston caliper.
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Here is an example of a short track (left) and superspeedway brake caliper.
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"We downsize the caliper for the bigger tracks," says Elledge. "We may tend to run at Daytona, balance-wise, more rear brake balance than we do at a Martinsville. At Daytona the only time you're stopping the car, you're stopping straight (usually coming down pit road). You can use more rear brake in the thing and it will slow it down."
Another substantial difference is found in the size and thickness of the rotors.
"The rotors are 180 degrees different from Martinsville (to Daytona)," Elledge says. "Martinsville rotors are 1 3/8-inches thick and the Daytona rotors are only 3/8-inch thick. The Martinsville stuff has got veins in it, and the Daytona stuff is a solid steel rotor with a bunch of holes in it.
"This is just to keep the rotating mass down for the speed. The braking force for Daytona is only good for basically one stop from 200mph down to nothing. So if you were to have to do that corner to corner, you would burn the brakes up really quick."
Pad thickness varies a great deal between short track and superspeedway cars.
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The brake pad size and thickness is much greater in the short track pad (top).
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"With the Daytona stuff we run steel rotors, and an aircraft-type pad that has a lot of metallic in it. It's very, very thin," says Elledge. "You go to some place like Martinsville and the pad thickness is 1 1/8-inches thick. It's a lot bigger pad, obviously, because the caliper size is bigger.
"As for the compounds, we've pretty much settled in on one for the front pad that we really, really like, and we run it everywhere, other than the speedways. We pretty much run it at every track from Michigan to Martinsville.
"But the rears we will juggle around a little bit. We'll probably fool around with the rear pads just depending on corner entry. Too much rear brake will get the car loose on entry. So we'll fool around with maybe a little bit harder pad in the rear.
"But we also try to keep as much rear brake on it as you can, because the more you can stop the car with all four wheels, the easier it's going to be on the brakes."
Keeping the brakes cool is essential on the short tracks and road courses. It is often a give-and-take situation.
"NASCAR mandates how many maximum square inches you can have open on the front grille area for the brakes," Elledge says. "The more square inches you have open on the grille, the less front down force the car makes (which gets more air to the brakes for cooling). You're constantly trying to balance that deal out to make it where you get enough air on the nose and where the car will turn, but yet not burn your brakes up.
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There is a huge difference in rotor thickness between short track and superspeedway cars.
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"We have an actual duct system that goes into the spindle in the center of the rotor, covers the caliper and has three-inch hoses. NASCAR allows you to have four, three-inch diameter hoses going to that brake duct assembly to cool it. A lot of the other places we'll actually run electric fans in the nose and not cut any holes in the front end."
Brakes even play a role in pit box selection at Daytona and Talledaga.
"When they make a green flag stop (at Daytona or Talladega), I always try to pick further down pit-road, because the brakes are so hot, you're trying to get off the racetrack and onto pit road as fast as you can," says Elledge.
If you're pitted too early on pit road, you may have a hard time getting stopped. A pit stall farther down pit road will give the brakes a little more recovery time so that they can cool off. "They're red when they get to you," Elledge says.
Elledge says the Watkins Glen road course is harder on brakes than even Martinsville.
"Watkins Glen is the worst racetrack for brakes," says Elledge. "Sears Point is just the opposite. Sears Point is probably the easiest track (of the short tracks and road courses) on brakes. You can go to Sears Point and not have to have a lot of air on the brakes.
"The thing with Watkins Glen is you're running at 175mph entering the inner-loop. So what happens is all the straightaways are a lot longer, so you're taking the car from a lot faster speed all the way down.
So what traditionally happens at Watkins Glen is you'll hear the driver complain of a hard pedal but it won't stop. The rotor temperatures have gotten so high that it will move material on the rotor, instead of using the friction of the pad, it actually just kind of swirls material on the rotor."
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