Corner Balance Calculator

Street Stock - Sportsman Cross Weight Calculator

Credit Rob Robinette - K9OJ

This calculator uses your racecar's four corner weights and calculates mass and percentages. We then generate target wheel weights to achieve a 50% Cross Weight or Null-wedge.
A 50% Cross Weight will yield a balanced handling car, one that turns equally well in both directions.
For turning left on a clay circle track you will increase the Null to Positive Wedge (example: 52%)
Positive wedge = Oversteer. Negative wedge = Understeer. Null-wedge = Balance (equal steer L/R).
For information on corner balancing see my corner balance how-to and this excellent article: Grassroots Motorsports » Understanding Corner Weights

Left Front         Right Front

Left Rear         Right Rear 

 Enter your corner weights as displayed on your scales and click 'Calculate'.
                        The example above is a Street Stock less driver with 10 gallons fuel. Tires aired to 10 pounds.

These are your current calculated weights as entered above:

Total MASS =

                               Front Weight = %

Left Weight = %           Right Weight = %

                               Rear Weight = %

Cross Weight =    50% is NULL-wedge (Wedge Delta)

Side-Bite =   Side-Bite must be positive for circle track racing.
This number is very important and should be recorded week to week, even to event.

Wedge = %    ∆ Wedge Delta should be positive for oval racing.
Negative Wedge = Understeer, Positive Wedge = Oversteer (this is best for clay track racing)

These target weights will yield NULL-wedge, balanced 50% Cross Weight:

Left Front = ∆             Right Front = ∆

Left Rear = ∆              Right Rear = ∆

    ∆ = change needed to get to target weight

Cross Weight =  @ %  - 50% is NULL-wedge

Side Bite at 50% will be This will increase as wedge is increased.

Wedge = %   Wedge Delta will equal 0 at 50% Wedge

Scaling your car:
You need a nice, flat and level surface for the scales. I highly recommend using a laser level to confirm the 4 scales are level to one another. Even 1/8 inch difference will make a difference, especially if you have stiff springs on your coil overs. I used a laser level to project a horizontal line above each scale and placed a ruler on the top of the scale to take a reading. All 4 scales must be within 1/8 of an inch. I used linoleum tiles to shim two of my scales to get them all level. Note: Once you have scaled the car, mark the floor and place each scale at the same location for every session thereafter.
Check your tire pressure and bump them to the hot pressure you run on the track. I use 2x6 wood planks as ramps to drive the car onto the front ramps then jack up the rear and lower it onto the rear scales. It's difficult to position all 4 scales so you can just drive up on all of them at the same time.
Before putting your car on the scales you need to power up the scales and zero them with no weight. Also double check that the scales are connected properly (RF cable to RF scale unit, etc.)
Once you get the car up on the scales you'll need to roll the car back and forth a few inches several times, being careful not to push it off the scales, to unload the suspension (as the car is lowered onto the scales the tires will need to spread out to unbind the suspension). You will have to repeat this every time you lower the car onto the scales.
 Note your ride heights and suspension changes to track your progress. When you adjust weight-jacks to get the desired corner weights your ride height will change, and vice-versa. Always document your current ride heights and your jack-screw changes each time you weigh and adjust. It's better to make many small changes than to try to balance your car in one big step.
You can also estimate your car's center of gravity (CG) height by using this page: CG Height Calculator

Cross Weight % = (Right Front + Left Rear) / (Left Front + Right Rear)

When balanced the Cross Weight % will be 50%

Bite and Wedge Delta are important for oval racers, especially on dirt ovals. Since oval racers only turn left we can balance the car for better grip in left turns.
Side Bite tells us how much we are favoring the left rear tire for better acceleration out of left turns. Bite calculation = LR - RR and a positive value means the Left Rear tire is carrying more weight so it will get more traction and bite, a negative value means the Right Rear is favored. Note: The more negative the bite the better chance the car will step out on turn exit.
Wedge is a term used by circle track racers and is simply another term for Cross Weight %. Oval racers discovered they could insert an actual wedge into the left rear springs to put more weight on the left rear (and right front) tires and it would help the car turn left and accelerate better. Today's oval racers add "wedge" by adjusting the right rear spring perch up, or the left rear down. This loosens up the right rear tire which puts more weight on the Left Rear and Right Front.
Adding "wedge" can be as easy as adjusting the LR weight jack. Add 2 turns and read your scales. A "positive" wedge will advance Oversteer. The driver must "counter-steer" back to the right in order to turn left without "looping" the car or turning into the infield. A "negetive" wedge should never be applied to a circle track racecar. This is dangerous and will cause the car to steer toward the outside wall. The driver must force a hard steer to the left and lift off the throttle to gain control; this is called Understeer. Note: The greater the "negative" number the more sweeping the turn radius. This means you should consider turn radius when adjusting "positive" wedge.br> Wedge Delta calculation (RF + LR) minus (LF + RR) and tells us how much extra weight is on the left rear and right front tires which gives them more traction or bite in left turns. For circle track we want a Positive Bite and Positive Wedge Delta. When Wedge is balanced at 50% then Wedge Delta will equal 0. Use caution...you can add too much Wedge Delta and make the racecar extreemely loose. Keeping track of Bite and Wedge Delta and what values work best for certain tracks and conditions can help us get our setup right with less time wasted in the shop. You should scale your car every week and double-check your percentage database.

A modified Corner Weight spreadsheet is available herespan>:  Corner_Balance.zip

Excel Corner Balance Spreadsheet Screen Capture