Commentary

You think pit stops are key? Wait until you check out bump stops

Kyle Busch was hot. Jimmie Johnson and Carl Edwards are hot. What may really decide the Chase? How about an $8 hunk of rubber, writes David Newton.

Updated: September 19, 2008, 3:20 PM ET
By David Newton | ESPN.com

LOUDON, N.H. -- Forget that Kyle Busch enters the Chase with eight wins and a 30-point advantage over Carl Edwards. Forget that Edwards enters with an average finish of 5.1 in the last six races, making him the hottest driver in the 12-car field. Forget that Jimmie Johnson enters with consecutive wins, as he did a year ago, making him a serious threat for a third straight title.

This Chase could come down to one thing -- a piece of rubber that costs anywhere from $8.50 to more than $500.

Bump stops.

We've heard about them for almost two years with the new car. Seldom does a Sprint Cup weekend go by that some driver or crew chief doesn't blame them for an ill-handling ride.

Four-time Sprint Cup champion Jeff Gordon hates them, saying they are in large part the reason he hasn't won a race this deep into a season (26 races) for the first time since his rookie year in 1993.

"That's the biggest inconsistency that we've had is whether we're on the left front bump stops, right front bump stops, front bumps upright, both bump stops, the timing of the bump stops," Gordon said as he prepared for Sunday's Chase opener at New Hampshire Motor Speedway.

"We've just had one heck of a time trying to get the front of the car to be consistent in and through the corner at a lot of tracks. And when you see us running good, it's usually because we've got those close and it allows me to do what I need to do."

Exactly what is a bump stop? It's a rubber doughnut inserted into the shocks or chassis -- but mostly shocks -- to prevent the front-end splitter from hitting the track as the suspension travels downward. They come in all different sizes and materials -- most polyurethane or rubber -- and are used in most street cars and trucks.

They became necessary with the new car because the distance from the splitter to the track is only four inches, almost half the clearance of the old car, which used coil binders made of metal.

They become even more crucial on flat tracks such as New Hampshire where the brakes are used a lot.

Teams that have figured out bump-stop technology have been the most successful this season, which is why you hear few complaints from Busch and Edwards.

And it is technology. Darian Grubb, the lead engineer for the teams of Dale Earnhardt Jr. and Casey Mears at Hendrick Motorsports, carries about 800 different bump stops to each race. Richard Childress Racing has six employees dedicated full time to bump stops.

Smaller-budget teams have been left behind.

"I don't think there's any such thing as figuring them out," said Todd Berrier, the crew chief for Kevin Harvick. "There are just so many variables, so many ways we can do it. You can have them share more of the load than the spring, the spring share more of the load, the sway bar.

"We have a better handle on it now for the direction we're going in the Chase, but we could also switch directions really quick and be back to where we are. There are just too many variables to say we've got it figured out."

Johnson's crew chief, Chad Knaus, shrugs off the bump stops as no big deal. But five months ago, before countless hours of testing, Johnson complained about the bump stops as much as anybody.

"When [the splitter] hits, it throws the car completely off the line and screws up the way it sticks to the ground," said Johnson, who is coming off wins at Richmond and Bristol. "You have to revamp the whole setup to get the car correct, unlike before by loosening a few screws or using a hammer.

"It's very challenging."

And whoever figures it out the best could have a big advantage in the Chase.

"It's the biggest change in our sport over the last year," Gordon said. "There's so much money, technology and development going into these things, it's ridiculous."

Bump stop background
"It's going to be safer racing. We're not going to blow out tires, and frames are not going to be hitting the track. It just makes things a lot simpler. The cost factor of building bump stop materials on the chassis and frame was going to get out of hand. So they did a good job of nipping it in the bud."

Those were the words of Elliott Sadler in 2001 after NASCAR eliminated bump stops.

No, this isn't the first time bump stops have been used in the Cup series. They were common in the late 1990s and through early in 2001 before they were ruled illegal. There actually have been cases since when teams were fined for using them.

But with the new car, the bump stops have proved more effective than coil binders on which the rub is metal to metal.

"On a smooth racetrack they literally ride on the bump stop instead of the spring," said Brett Bodine, who helped develop the new car for NASCAR. "In the development of the bump stop, it has to have some squashability. You can't just put a solid piece of steel in there because when it hits, it's rock solid."

The thickness of the bump stop varies from track to track. Most teams have it figured out through on-track testing or the use of the seven-post shaker before they leave home.

"We may not be 50 percent through this development program," said Hartwell Pritchett, the shock specialist at Gillett Evernham Motorsports. "It's one of those things we don't know what we don't know yet.

"By the end of the season, I suspect we'll be a lot further along in development until the next polymer is developed."

To test the current bump stops, teams drill holes into the splitter and insert plastic screws with a stop nut that extends through the splitter. Engineers can determine by looking at the amount of plastic left after a run how close the splitter is to contact with the ground.

We work with it every day and still don't understand all the parts to it.

-- Darian Grubb

Adjustments can be made with packers that usually are an eighth of an inch thick. It's a lot like stacking a sandwich until you get the desirable ingredients to be filling, or in this case give the driver the best feel.

"There's plenty of scenarios you can play with," Grubb said. 'That is what everybody has been doing the last 10 weeks or so, playing with different scenarios to see what they need to go with into the Chase.

"You want to get as much of the splitter on the ground as close as you can for aero gains, but you can't take all the springs out. It's got to be able to handle the rest of the way around the track. The bump stop gives you a little bit more tuneability of keeping that on the ground without having to get a bunch of rebound on the shocks."

Roush Fenway Racing cars appear to have solved the bump-stop mystery, or at least come to grips with it. Edwards, Greg Biffle and Matt Kenseth made the Chase, and David Ragan was close.

Team owner Jack Roush said Ford engineers played a big role in developing new material to help give their drivers a good feel on the track.

"The computers are hammering up there on all the predictive and analysis things for the racetracks that we're going to in the Chase, and we think with their help we'll be able to offset some of the problems, some of the frustrations that the drivers have had that they've come back and blamed on the bump stop," he said.

"But it really isn't just the bump stop. It's the nature of the whole car being limited in terms of the areas you can work in."

Berrier agreed, but said some of the most significant gains RCR has made on the track are a direct result of bump stops.

"As we got better, it probably shares over half of how we got there," he said. "There's no way that it couldn't help you refine the car and get it better. Everything is so close. You're looking at only a half a tenth of a second from being the best car on the track to the worst."

Bumps in the road
Gordon sarcastically joked earlier in the year that Hendrick Motorsports was looking for manufacturers in Dubai to design a special rubber or plastic for bump stops.

He's that frustrated with them.

"The inconsistency isn't just with our performance, it's with these bump stops that we have to run on," said Gordon, who will start the Chase 80 points out of first. "I can't stand them, and trying to get them figured out is just near impossible.

"Some have done a better job with it. Maybe it suits come guys' driving styles better, but it's one of the things that's challenging us."

Grubb wishes he had an answer for Gordon. He's not sure there is one.

"We work with it every day and still don't understand all the parts to it," he said.

Bodine laughs at the complaints, but he knows if they weren't about bump stops they would be about something else.

"It's easy to complain about something like that and say, 'Hey, we've got to figure it out. They've got something,'" he said. "People are going to figure them out. Some aren't."

The ones that do, or already have, will win races and stay competitive in the Chase.

Those that don't complain, watch out.

"Drivers are always going to complain about something," Knaus said. "They were complaining about the coil bindings a couple of years ago. It's a race car. It's going to go fast, and when it doesn't you're going to blame it on something.

"It's not just the bump stops. It's trying to figure out what the car needs and what the driver needs."

David Newton covers NASCAR for ESPN.com. He can be reached at dnewtonespn@aol.com.

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