Chassis Adjustments - Don't Forget!

One of the most enjoyable challenges in stock car racing is finding that perfect setup package that makes the race car feel like you've got Velcro tires and you're racing on a felt track. Like any pitcher throwing a perfect game, or a golfer hitting a hole in one, nailing that absolutely perfect setup is an all-too-rare occurrence and should be enjoyed whenever possible.

Modern race cars, even Street Stocks and Legends Cars, allow many tuning options. But that can sometimes be a double-edged sword. With so many options available, it can be easy to confuse exactly what does what, or even overlook a tuning change that can take your race car's handling from good to great. Most of us find those chassis adjustments that work well and go to them more often then the rest. That's OK, and even the Cup crew chiefs do it. But what you shouldn't do is completely ignore other tuning options available to you. It's like throwing away half the wrenches in your toolbox.

Stock Car Racing asked several chassis builders what adjustments they most often have to remind their customers to check. And then we asked crew chiefs and racers the same question. Their responses run the gamut, so we're presenting what we feel are the most helpful tips.

Chassis builder Gene Leicht of Leicht Race Cars says he often has to remind his customers to check the sway bar in the front of the car. Most racers won't forget that they have a sway bar in the car, but since it's usually contained within a tube on a handbuilt chassis, it's easy to forget the size of the bar in there.

If you can't see the sway bar size right away, it's always helpful to take a moment to double-check what size is in the car. It's possible that a random bar was put in during the setup process for the purpose of scaling the car.

This is not necessarily a chassis adjustment as much as it is a reminder to check for damage when your race car mysteriously loses its handle. Chas Howe of Howe Racing Enterprises gets calls from customers complaining about a chassis that will not respond to adjustments. He says his usual test is to ask them to change the rear stagger in both directions (right rear larger diameter and right rear smaller diameter). If the race car's handling does not change significantly, then he says the culprit is almost always a bent rearend tube.

Whenever the rear wheels make contact with another object, either the wall or the wheels of another race car, there is the potential to bend an axle tube on the rearend housing. This can often be difficult to detect without completely restringing the car, including squaring the rearend. A bent axle tube throws off the rear-wheel geometry and changes such as stagger or putting a little angle into the rearend won't have much effect on the car. The good news is Howe says that often only the axle tube will be bent while the rearend bell will still be good, so the rearend can be repaired instead of junked.

Instead of pointing to specific chassis adjustments, race car builder Charlie Barham of FNO Race Cars points out that you often must define where on the track the race car needs help first. This is because different components will have greater influence on how the tires maintain traction, depending on what the driver is doing. For example, on turn entry, the brakes are the predominant force in play. On turn exit, brakes are obviously no longer an issue, but the throttle, specifically how power is put to the ground, is the main factor affecting the car.

To take it a step further, if the handling problem occurs on turn entry, you should concentrate on the front suspension because the car is decelerating and the weight transfer is over the front wheels. Monkeying around with the rear in an attempt to fix a handling problem on turn entry will not have as much of an effect because the rear wheels are only lightly loaded.

On the other hand, the driver is applying progressively more throttle during turn exit so that the weight transfer is over the rear wheels. Now you should turn your attention to what's going on in the back half of the car. This can help you separate the many available chassis adjustments into areas where they will be most helpful. Make front spring changes to dial-in the car from turn entry to the center of the turn. Save rear spring changes for perfecting the car from the center off. A track bar change, for example, should come to mind as a priority if your car isn't handling well when accelerating out of a turn.

When determining where on the race car to focus your attention for chassis adjustments, always begin by trying to fix the handling problem that occurs first. For example, if the driver says that the car is tight in the center of the turn and loose off, do not begin by trying to fix the loose condition on turn exit-even if the driver says it is the most bothersome of the two problems. This is because the handling problem that happens first often influences the handling problems that come later, even if they seem to be complete opposites at first.

Let's take a closer look at our example. Whenever a car is tight, it isn't responding to the driver's steering input. When the car is tight in the center of the turn, the driver must continue turning the wheel while slowing down until the front tires finally regain traction. Because the driver must compensate for the handling problems, he or she will almost always turn the wheel farther than you would if the front wheels were not sliding. Now when the front tires begin to regain traction, the front wheels are turned farther than necessary, and the rear end tends to break loose when the driver tries to pick up the throttle. By fixing the push in the center of the corner, the driver will have to turn the steering wheel less, reducing the tendency for the car to get loose on turn exit.

We also talked to former Winston Cup crew chief and current racing analyst Larry McReynolds. Interestingly, both McReynolds and Barham recommend swapping out the bushings in the suspension arms that connect the rear end to the chassis. In most cases, you want to use steel monoballs or Heim joints to remove any uncontrolled flex from the suspension. But this creates a rear suspension that works well when the tires move vertically but has no give to help control wheelspin. This is the case only in asphalt race cars with non-leaf-spring rear suspensions, where the rear end is locked in and not allowed to roll.

When the driver picks up the throttle on turn exit, a high-torque race motor can shock the driveline and break the rear tires loose. Typically, the driver will complain about not having enough forward bite. By switching out the steel suspension bushings and replacing them with rubber, you add a little flex to the system. Now when the driver picks up the throttle, the suspension bushings give a little bit under acceleration, which can keep the rear wheels from breaking loose as easily. Essentially, it's just a cheap form of traction control because it helps dampen that first blast of torque to the rear wheels on acceleration.

No matter how experienced you are as a racer, it's virtually impossible to remember every chassis adjustment and how it affects your race car. Even Larry McReynolds, who won 23 races as a NASCAR Winston Cup crew chief, says he depended on a list of all chassis changes available to him and how they can potentially affect the race car.

"As a crew chief, I always kept a list of everything on the car I could change in my notebook," he says. "Whenever I ran into a problem, I could look at that list and see if I was overlooking something.

"I remember that really paid off for me once when I was working with Ernie Irvan at Robert Yates Racing. It was 1993 and we were preparing for the fall race at Lowe's Motor Speedway. NASCAR had come up with the "Five and Five" rule. That means that the front valence had to be at least 5 inches off of the ground and the rear spoiler could only be 5 inches tall.

"With only 5 inches of spoiler, all the teams were having trouble getting loose in the corners. We had tried all the usual tricks but weren't having any luck. That Friday night I sat down with my list and began looking over all the setup possibilities once again. Finally, I hit on 'wheelbase.' That's when I remembered I had that car a quarter-inch longer on the left side to help it turn.

"So when the garage opened that Saturday morning, the first thing we did was shorten the wheelbase back up on the left side until it was the same or maybe even just a little bit shorter than the right-side wheelbase. That change fixed the problem of getting into the corner loose without making it push from the center of the corner on out.

"I think we must have been one of the only teams to think of changing the wheelbase for that race because Ernie led over 300 laps in that race. He really just ran away with it, which was a lot of fun to be a part of. Wheelbase isn't normally a chassis tuning change you make, but you have to be able to take advantage of every tool you have available because sometimes it can give you an advantage on the competition."