# How to Use Corner Scales

February 21, 2012

### Cars are typically weighed with corner scales--i.e., a scale under each wheel. Learn how to place, configure, and take measurements with a corner scale.

Corner scales are used to measure your car's weight at each wheel or "corner." They allow you to monitor how suspension settings, ballast and weight reduction affect these corner weights. While corner scales are relatively unnecessary for most people, they can be very useful to a race car driver or anyone interested in pushing their vehicle's performance.

Ideal Weight Distribution
For vehicles that use a coil over adjustable shock suspension system, such as racecars or rally cars, the tool can be effective for determining the corner weight or the weight over each individual tire. Under ideal conditions the weight on a vehicle should be distributed equally and have 50 percent of its weight on the left front and right rear tires, and 50 percent on the left rear and right front tires, or 25 percent on each tire. The closer to this ratio, the better the vehicle will perform.

Proper Setup
Using corner scales is relatively easy, but setting them up properly first is very important. To function accurately they must be setup so that they are all at the same height and level with each other. In most cases, a set of racing corner scales comes with an adjustable fixture that allows for this, and acts as a platform with ramps so that you can get your car on the scales.

Once the fixture is put together, adjust the so the scales are at the same height and level. Use a long level to guide your adjustments. First set side-to-side levelness, and then front to back. Double check these and check for diagonal levelness as well.

Using Corner Scales
Drive your car up onto the scales via the ramps and then record the numbers on each scale. If you must get out of the car to do this, be sure to put the equivalent of your weight into the driver's seat and footwell. Add the numbers from the front two corners together. This is the weight on the front wheels of your car. Divide this number by the sum of all four scales to determine the percentage of weight on the front axle of your vehicle. Subtract this number from 100 to find the rear percentage. A similar calculation can be completed to determine the percentage of weight on the left and right side of your vehicle.

Weight Bias
The front to rear bias and the side-to-side bias of your vehicle's weight influence how it handles in high performance driving situations. Get your vehicle's side-to-side weights as close to each other as possible. This will help your vehicle behave similarly in left and right turns. This can be accomplished by selective weight reduction or ballasting, or even moving components around such as the battery or fire extinguisher. Similar methods can be used to adjust front to rear weight bias.