A setup crutch is defined...
A setup crutch is defined as any change made in an attempt to improve the handling balance that does not address the real cause of the problem.
Chassis setup crutches have been around forever, and their methods change with the evolution of setup trends. What was common 10 years ago or even 5 years ago may not be common today. We need to know what racers are doing to mask basic setup problems so we can avoid making the same mistakes.
We will outline common crutches in addition to past, present, and future setup trends for both dirt and asphalt. Both forms of stock car racing have their trends and have evolved a lot over the past few years. We'll look at adjustments teams make to try to make their cars handle better, even though they'd be better off going in other directions.
What we have definitely learned is the fastest setup on a two- or three-lap run may not be the fastest setup at the end of the race when the track surface has changed and we are running on worn and heated up tires. Our fast setup must remain fast until the checkered flag falls. The key to that end is to understand the true definition of balance so that we can have the desired consistency needed to be a winner.
We need to evaluate how we are setting up our cars, the type of racetrack we will be running on, and the length of the race. For example, if we are running 25-lap sprint races with three cautions thrown in, our desire for the ultimate fast 5 or 10 laps may cause us to deviate from a setup that must last 100 or more laps under a long green-flag run.
A race car setup crutch could be defined as any change that is intended to solve a handling problem but does not make the car faster and/or causes other problems to appear at other points on the racetrack. We will explain how some specific crutch methods work and why racers think they need these particular crutches. Then, in future articles, we will expand on each topic to explain how to develop more efficient ways to accomplish the same goals.
A driver may make adjustments...
A driver may make adjustments to his or her driving style to try to fix a handling problem, such as a car's inability to turn well.
The following are the most common setup crutches.
Driving Style The way the driver is forced to drive the car can sometimes be a crutch. How many times have we heard a driver say that the car is loose even though it appears tight on entry and in the middle of the turn? What the driver is doing, but is most likely unaware of, is steering excessively in an attempt to overcome a tight condition. This excess steering definitely creates more traction at the front tires to help balance the car. Here is the reason.
The way the driver is forced to steer the car can be an indication of a problem with the setup and is one of the top indicators that may lead to a crutched setup. A lot of research has been done on tire characteristics related to traction. Tire engineers learned that more traction is generated at increased angles of attack in the direction the car is turning. This means that more traction will be gained at the front tires as the wheel is turned farther from the direction of travel, up to a point. This is referred to as the angle of attack.
When the steering gets to an extreme angle of attack, the traction at the front tires will suddenly go away, causing a severe push. But as the steering wheel is turned a few degrees more than normal to force the front end around in a tight car, the handling balance begins to change.
As the driver enters the turn, backs off the throttle, and applies the brakes, he or she begins to turn the steering wheel and must turn it sufficiently so that the front end will come around. If the car's setup is too tight, the driver will need to turn the wheel further than would normally be necessary in a car that is neutral in handling balance.
This dirt Late Model car is...
This dirt Late Model car is very neutral in handling. Note that the front wheels are pointed straight ahead and the car is mostly in line with the direction of travel.
When the driver has turned too far, the traction balance reverses from tight to loose as the front traction begins to exceed the rear traction. At this point the car will start to feel loose. This can happen very quickly, and the driver will swear that the setup in the car is loose.
Just past midturn, the car will definitely feel loose to the driver. The exit performance off the turn will also suffer as the driver gets on the throttle and the car becomes more loose from power-induced rear wheelspin. The average temperatures of the rear tires will probably be higher than the average of the front tires due to the tires spinning with the loose-off condition.
The crew will often interpret the higher rear temps as a sign of a loose condition and think the car needs to be tightened up, but they are wrong. It is already tight, so a lot of valuable time is wasted searching for solutions to this basic problem.
A great way to quickly discover the handling balance for your car is to have the driver roll through the turn below the maximum speed. The amount of steering input needed to just drive around the turn should be mentally noted. Then the driver should take the turn at full speed and again note the amount of steering input.
If the steering wheel is turned more than when the car was rolled slowly through the turn, the car's setup is too tight. Many drivers are very surprised at the outcome of this test. A lot of time can be saved by doing this simple exercise, and it works for dirt or asphalt. For dirt, the initial entry to the halfway point in the turn is where we look for excess steering to the left for a tight car, or countersteering for a loose car.
The Big Bar Soft Spring (BBSS)...
The Big Bar Soft Spring (BBSS) setups are not always the fastest. We tried an older Midwest flat-track setup that was as fast or faster than the BBSS cars and developed much more traction off the corners.
Rear Spring Rates We are often in search of more bite off the corners or more aero downforce. To accomplish those goals, we can either soften the right-rear (RR) spring for more bite or stiffen the RR spring to force the nose down on the left side for better aero effect. If your car is too tight or loose in the middle, the rear springs may be too soft or the spring is split too much either way. If the setup is loose, the RR spring may be too stiff.
A common trend in dirt and asphalt racing has been to run a stiffer RR spring than we were used to a few years ago. This can be overdone, so we must compensate to correct the car's handling balance due to excessive manipulation of the car's attitude. Is this all necessary in order to go fast? We experimented and found some interesting conclusions. The first test was with an asphalt Late Model on a fairly flat track.
BBSS vs. Conventional We set up a car for a Late Model touring series (we won't divulge which one) in which the Big Bar and Soft Spring setups were the trick. This series even had a few teams with traction control (not our conclusion, but the consensus of most teams and the officials). We participated in a test day with most of the top cars in the series present.
We decided to deviate and see what would happen if we set up the car just like a typical mid-'90s Midwest flat-track car, using a 350-pound LF, a 325-pound RF, a 185-pound LR, and a 175-pound RR spring. This is basically the flat-track setup I developed for Brian Hoppe's team when he won the 1999 RE/MAX Challenge Series. We also set the crossweight to around 58 percent. We practiced on tires that were used in the previous race and never put on stickers.
Our lap times were as fast or faster than the other cars on not-so-fresh tires. After the other cars had made their sticker runs and put about 20 more laps on those tires, we were still as fast as them, using our 200-plus-lap tires. On longer runs, we were consistently quicker toward the end of the runs, and we got off the corners better than even the T/C cars. Our driver could flat-foot the car off a slippery Turn 4 all day long.
We attended a closed test...
We attended a closed test in which we changed everything we could to see what the results would be. The runs were recorded with data acquisition help from PI Instruments. What we found was surprising, to say the least.
Dirt Car Setup Test We recently attended a closed test with dirt Super Late Model cars. We found interesting trends, but we will report more on this test later, when the data has been properly evaluated.
We started out with what would be described as the current trend in setups. The Panhard bar was attached to the left side of the chassis and was angled with the left mount much higher than the right mount. The left side upper trailing arms were set higher, and the LR spring was mounted in front of the rear end. The front springs were 400 LF, 375 RF, and the rear springs were 275 LR, 275 RR. The car was evaluated for front moment center location, and throughout the test the car turned in well and was neutral in the middle of the turns. The track was moderately slick, and the main problem was getting bite off the corners.
We changed all the bar angles left and right, changed the lift arm shocks and spring, and even replaced the right lower trailing arm with a pushrod. None of those changes produced better lap times, and some adjustments felt bad to the driver.
Then we did something crazy. We reversed the Panhard bar from left chassis to right chassis mount. This configuration completely changed the attitude of the car. Instead of the rear of the car being high and the LR tire moving forward, the car sat low in the turns, both rear tires tucked inside the wheelwells, and the car ran the same lap times. The driver actually went a few tenths faster down low, but moved up after two laps.