Wheel Scales - Maximize Your Scale Knowledge

Most racers have heard about or used wheel scales in the process of car setup. These scales, when one is put under each wheel, will give you the corner weights of the car.

There are several kinds of wheel scales. Often the least expensive are the lever scales. See our Web site, stockcarracing.com, for more information on lever scales. These consist of a fabricated lever with a pivoted leveling plate in conjunction with inexpensive bath scales. The visual weight is then multiplied by the lever ratio, commonly 4:1, to get the actual weight. These scales will work to about a 10-pound repeatability. The downside is the setup time. The car must be jacked up about 6 inches so that the scales can fit under the tires. The plate must then be centered under the tire. When the jack is lowered, it will roll in a direction toward the handle. This must be anticipated to keep the tire centered on the plate. Due to the suspension travel characteristics, the lateral movement of the wheels must also be considered. With these scales, you do all of the math yourself for true weight, crossweight (the percentage of weight measured from the right front to the left rear against the car's total weight), left weight, and rear weight. You also get a little exercise walking around the car to read each scale.

I don't want to frighten you in regard to the lever scales. I used some home-built ones for years. I spent a lot of time in order to get results, but that was the budget I had. In retrospect, I should have spent the money on a set of digital scales instead of buying new cylinder heads. Yes, electronic digital scales are expensive, beginning around $900. Just remember that any race car part is expendable and will likely break in a season or two, while a good tool can be used on many race cars for a long time.

The digital electronic scale set is definitely preferred, with a repeatable accuracy of about a pound. Of the several manufacturers of these scales, you will find different features. However, all of them will do much of your math both in actual weight and in percentage. The construction of these scales can be likened to a flat pad about 16 inches square and 2 inches thick. These pads are thin enough that simple ramps, or purchased ramps, allow the car to be rolled onto the scales without having to jack it up.

Another nice feature of a digital scale is that the front wheels can be steered with the car still on the scales. Bruce Rhoe of Intercomp assured me this was OK. Not only does this allow you to set caster and camber on the scales, but you can also see the effects of caster and camber changes on crossweight.

These scales interconnect with cables going to the digital readout box, where most of the math is done for you. You read all the numbers at one place.

To keep repeatable accuracy, each scale is labeled for its position (RF, LF, and so on). Also, each connecting wire is labeled so that it can be connected correctly.

In the Stock Car Racing shop (Sleepy's Workshop), I have a set of Intercomp scales that I have used for several years. Having the convenience of digital scales has been worth the wait. I just waited too long to get a set.

In order to demonstrate the use of these scales, I built a model. It is roughly a 30 percent scale of a GM metric car. It was made of 3/4-inch square tubing in a rectangular form. A long coupler nut was welded to each corner. Through this, an all-thread jack bolt was inserted. This allows the corner adjustment to simulate the suspension adjustment on the fullsize car. Under each jack bolt, I placed a leftover Honda valvespring to allow chassis movement. At this point, the model had a chassis and springs, but not enough weight. A&A Manufacturing lead weights were clamped to a 2-inch square tube. A pair of these weighs 25 pounds when the bolts are included. This tube could then be moved around to simulate the weight percentages that might be found in a fullsize stock car. Another pair of weights was added to bring the total weight of our model to 56 pounds. One of these weights was used to simulate the effect of physically moving weight around the car.