Corner Weight Calculator math takes four scale readings and returns cross weight, nose and left percentages, the target corners, and the ballast needed to square up left and right.
Add Driver or Ballast
Weighed the car empty? Add the driver or ballast here and every result updates as if it were aboard. Set weight to 0 to skip.
Top View of Your Corner Weights
Ballast Planner and Corner Extremes
Balancing a Car With the Corner Weight Calculator
The Corner Weight Calculator turns four scale readings into cross weight, nose weight, and left side weight. It also gives the target weight for each corner and the ballast needed to even up the sides.
Autocrossers, road racers, oval and dirt racers, and RC drivers use it after a scale session. It shows which diagonal is heavy and how much weight has to move across it.
Scale Readings and Setup Goal
Enter the weight on each pad of the Corner Weight Calculator in pounds or kilograms, along with the wheelbase and track width in inches or millimeters. The metric setting uses 1 lb = 0.45359 kg and 1 in = 25.4 mm.
The “Where the Car Runs” menu changes the advice in the alert box. Road course, autocross, street, and RC reset the target to 50%, while the two oval choices leave your own target in place. The target accepts anything between 30% and 70%.
Cross Weight and the Diagonal Math
Cross weight, also called wedge, is the share of the car’s weight carried by the right front and left rear together. Grassroots Motorsports defines it this way. Above 50% the car has wedge, and below 50% it has reverse wedge.
$$\text{Cross} = \frac{RF + LR}{LF + RF + LR + RR} \times 100$$
Some scale boxes and calculators report the other diagonal, LF plus RR, instead. The two always add up to 100, so 49.1% on RF plus LR is the same car as 50.9% on LF plus RR. Mixing the two turns a small correction into a large one in the wrong direction.
To reach a target, the diagonal has to gain or lose the difference in pounds. Half of that goes onto each corner of the light diagonal and comes off each corner of the heavy one.
$$\text{Shift} = \frac{\text{Target} – \text{Cross}}{100} \times \text{Total}$$
Adding the Driver to an Empty Car
Setup guides such as Autocross to Win insist the driver, or an equal weight, is in the seat during scaling. If you weighed the car empty, the ballast panel adds the driver using the same lever rule as the Axle Weight Distribution Calculator. It works front to rear by wheelbase and left to right by track width.
At the defaults, a 180 lb driver sits 55 in behind the front axle and 14 in left of center. That adds 59 lb to the LF, 22 lb to the RF, 73 lb to the LR, and 26 lb to the RR.
The driver changes more than the total. Without him the default car reads 50.1% left and 48.9% cross, and with him aboard it reads 51.4% left and 49.1% cross. Scaling empty and correcting to 50% would leave the car off once the driver climbs in.
Turning Scale Numbers Into Adjustments
The hero figure is cross weight on the RF plus LR diagonal. The line below it gives the other diagonal, so either convention can be read straight off the result.
Nose Weight and Left Side Weight
The first card shows front and rear percentages, and the second shows left and right. At the defaults that is 52.5% front and 51.4% left on 3,180 lb.
Longacre Racing, which builds race scales, says turning the jack screws will never move left side or rear weight. Only moving mass inside the car changes these two numbers, which is why the cards say so.
Target Corners in the Corner Weight Calculator
The third card gives the pounds that must move across the diagonals and the four corner weights that would hit your target. The defaults need a 30 lb shift, split as about 15 lb per corner.
That gives targets of 813 lb RF, 778 lb LR, 857 lb LF, and 734 lb RR. These keep the front and left percentages exactly where they are, since corner balancing only trades weight between diagonals.
Rear Bite and Front Split
The fourth card shows bite, which is the left rear minus the right rear. The defaults read +14 lb, with the left front 74 lb heavier than the right front.
Bite is a dirt oval number. Racers on scale forums describe it as the left rear load that helps the car drive off the corner, and a heavier left rear gives more of it.
Ballast Planner and Corner Extremes
The fifth card works out how much ballast would bring left and right side weight level. It mirrors the driver’s position onto the light side, and at the defaults that takes 189 lb.
Grassroots Motorsports notes that many cars cannot reach 50% left weight because of driver offset. The planner shows the cost in pounds, so you can judge if it is worth carrying. It also reports how far the ballast would move cross weight, which is only 0.08 points here.
The sixth card names the heaviest and lightest corners and shows how the driver or ballast spreads across the four pads. The LF is heaviest at the defaults, carrying 27.4% of the car.
Which Spring Perches to Turn
To add cross weight, raise the RF and LR and lower the LF and RR. To remove it, do the reverse.
Spreading a change over all four corners, rather than cranking one, helps hold the ride height. After each change, bounce the car, settle it, and enter the new readings in the Corner Weight Calculator.
Corner Weight Calculator Pitfalls on Scale Day
Corner weights, wheelbase, and track must be above zero. Ballast weight and its side offset cannot be negative. If the ballast position would lift a wheel off its pad, the tool stops and asks you to place it between the axles and inside the track.
The math assumes a level pad surface and a settled car. Longacre notes that a half-inch shim under one corner shows up on the scales as a cross weight change, so level the pads with shims or trays first.
Setup Errors That Skew the Readings
Leaving the sway bar connected lets it hold the car in a twist. Longacre and the 944 Spec corner balance guide both have you disconnect it before weighing.
Weighing with the wrong fuel load or unequal tire pressures also moves the corners. Set the pressures and pick one fuel level, such as race start or a half tank, and use it every time.
Skipping the bounce after a change leaves bind in the bushings and ball joints. Roll the car off and back on, or rock each corner, before reading the pads.
Corner Balancing Questions From Racers
What is a good cross weight percentage?
For road racing, autocross, and street cars, 50% is the usual goal because the car then turns the same both ways. Oval cars run more wedge on purpose.
One chassis builder on Physics Forums lists 51 to 52% for street stocks, with more for lighter modified classes. Treat those as class starting points, not rules.
Does corner balancing change front to rear weight distribution?
No. Turning the spring perches only moves weight between the two diagonals.
Front, rear, left, and right percentages stay the same, as Trackspec Autosports and Longacre both point out. Changing them means moving batteries, ballast, or the seat.
Is cross weight the same thing as wedge?
Yes, both terms mean the RF plus LR share of total weight. Circle track racers say wedge, and road racers more often say cross weight or diagonal balance.
What does bite mean on race scales?
Bite is the left rear weight minus the right rear weight. It matters most on dirt ovals, where left rear load helps the car drive off the turn. At the default readings the Corner Weight Calculator shows +14 lb of bite with the driver aboard.
Can you corner weight an RC car?
Yes, with four small scales or an RC corner weight system. The same percentage math applies at any scale, and most RC tracks turn both ways, so 50% cross is the usual target.
RC tuning guides suggest shimming ride height on opposite corners or moving the battery and electronics to adjust it. Enter grams in the weight fields and set the driver or ballast weight to 0. The percentages come out the same, even though the unit label still reads pounds.