An accurate set of scales is a vital tool for any racing program that hopes to see victory Lane regularly. This is true no matter if you are racing Pure Streets, Mini Stocks, Super Late Models or Sprint Cars. Weight plays a large impact on the handling of a car, and how that weight is distributed plays an equally large role in how your race car handles during acceleration, deceleration, and cornering. Since we are talking about dirt track racing here, all three of those things are happening at least twice every lap, so you’d better believe being able to precisely map the weight distribution on all four tires is critical for success. After all, you may be able to luck out and hit on the right setup, but without a set of scales (among other tools) you will likely never be able to find it again.
We recently spoke with Intercomp’s Scott Elmgren about the questions dirt track racers most often have when it comes to using racing scales. Intercomp makes a wide range of four-corner scales as well as other setup tools for racers. Today, Intercomp has ultra-accurate scales designed not only to make racers’ lives easier, but also to help them improve their setups for greater success on the track. Besides simply telling you the weight at all four corners of the car, Intercomp has scales that can actually calculate a car’s center of gravity and include a very useful target-tune feature that helps you get your setups right where they need to be with less time spent moving lead around. There is even an option to read and record weights on your iPhone or iPad through Intercomp’s iRaceWeigh technology which definitely beats kneeling on the floor transferring numbers from an old-school console to a spiral notebook.
If you are just starting out, you can get baseline setup numbers from your chassis builder or more experienced racers at the track. These numbers will be your target when first scaling the car, and as you gain experience you can adjust from there.
“To get an accurate reading from any set of scales, it is critical to make sure the scale pads are sitting on a level plane,” Elmgren says. “Small angles can throw off your readings significantly. Leveling the scales can be achieved in a number of ways, including shims or with the use of scale pad levelers. Intercomp’s Billet Leveler with a roll-off pad is a popular item among racers for its durability, convenience and the ability to roll the car back and forth after adjustments to unbind the suspension.”
Before scaling a race car, you need to make sure it is as race-ready as possible. This means fluid levels should be correct, including coolant, transmission and rear end fluids and about half a tank of fuel. Your chassis and suspension settings such as camber, right height and even wheel spacers should be set just like you plan to be when you roll off the trailer at the racetrack. Also, don’t forget the driver; he or she must either be sitting in the driver’s seat when scaling the car, or you can use sandbags or other forms of weight to simulate the driver.
Before you put your race car on the scales, double check to make sure all four pads are level (as we’ve already mentioned), turn on the scales and hit the zero button so that every pad reads zero for the weight figure. Now, either roll the car up on the scale pads if you are using role-off pads, or jack up each side of the car and slide one pad under each wheel. Before taking a scale reading make sure to bounce each corner of the car once or twice to make sure the suspension is settled and not binding. This is important because frame height can influence the percentage of the car’s total weight over a particular wheel.
A quality digital scale such as those Intercomp sells will tell you the weight at all four wheels, the total weight, and even do some calculations to tell you your percentages to greatly simplify the process of installing your race setup.
Different types of racing will often place an emphasis on different things when scaling a car. For example, oval track asphalt racers will usually place the greatest emphasis on the percentage of weight over the front wheels versus the rear, the left side percentage and cross weight. Cross weight is the weight over the right front tire plus the left rear tire divided by the car’s total weight.
Dirt track racers, while just as interested in dialing in the right front-to-rear percentage and left-side split, normally are much more concerned with “rear bite,” or simply “bite,” than they are cross weight. Rear bite is basically a simpler form of cross weight that places an emphasis on weight at the rear of the car. It is calculated by taking the weight over the left rear tire and subtracting from that the weight over the right rear. So, instead of talking in terms of percentages as you do with cross weight, bite is referred to in pounds. For example, if a racer says he runs 50 pounds of bite that means he has his lead placed so that there is an extra 50 pounds of weight over the left rear wheel versus the right rear.
Controlling rear bite is very important for dirt racing because it is so difficult to find the right balance between sliding the rear car out to help the car turn while also getting maximum forward traction on turn exit. Unfortunately, the optimal amount of bite varies wildly with several factors, so we can’t give you a specific number to shoot for. For example, just in the dirt late model class, we know that rear bite can vary from one driver to the next anywhere from 30 to 200 pounds depending on chassis manufacturer, track configuration, tires and even horsepower and driving style. We spoke with one driver to often switches from the crate engine class where the horsepower hovers around the 400 range and a limited class where the engines produce between 600 and 650 hp, and he says simply switching engines requires him to change his rear bite by just under 50 pounds.
As a general rule if you want your car to be tighter, add more bite. This can be useful if the track goes dry slick towards the end of the night. But be careful because overdoing it and adding too much rear bite can make you to lose on turn entry. Likewise, if the track has lots of grip and you’re having a hard time getting the car to turn, you can help the rear end break free by taking out some bite.
When adjusting your weight bias, make sure to always bounce the front and back of the car after any change to resettle the suspension. Moving lead ballast weights is the easiest way to change weight bias on your car, but be aware that frame height changes can also do the same thing. So if you use coilovers or jack screws to adjust your frame height, be aware that it will also affect your weight percentages.
Of course, that phenomenon can also be useful for making small adjustments to bite. If you want to adjust your rear bite at the race track, it isn’t practical to start unbolting and moving lead. Instead, running the jack screw or coil-over adjuster down (clockwise) will increase bite, while doing the opposite will decrease it. If you need to keep your ride height consistent so that you don’t throw off other suspension settings, you can do the opposite at opposing wheels.
For example, if you increase bite by bringing the screw jack on the left rear wheel down by a half turn, you can keep your ride height stable by instead putting a quarter turn down in the left rear and right front and a quarter turn up in the right rear and left front.
That’s just one of the many tricks possible when setting up your race car, but be careful to always document all your changes so that you can return to your baseline whenever you need to. For free downloadable setup sheets to help you track all your setup changes no matter what scales you use, check out www.Intercomp-racing.com.