Use this to get an idea of the CG of your vehicle. This is useful for other calculations, like anti-squat on a 4-link car!
Finds center of gravity height by weighing one axle with the car level, then again with the other end raised.
How to weigh the car
- Set the car up race-ready: fuel, fluids and driver (or ballast in the seat) as raced.
- Lock the suspension at ride height, for example by swapping the shocks for solid links. Any suspension movement while raising the car ruins the result.
- Pump the tires up hard so they don’t squash when the weight shifts.
- Weigh the car level. Record the total weight and the weight on the axle you’ll keep on the scales.
- Raise the other end 10–20 inches, measured at the axle centerline. Raising it more gives a more accurate result.
- Weigh the same axle again. Repeat the raised reading two or three times and average them.
The weight change is small, often only 10–30 lbs, so scale accuracy matters. The results show how much each pound of scale error moves the answer.
No scales? Estimate it
- V8: CG height is commonly estimated at camshaft height.
- Inline 4 and 6: don’t use the cam height. On overhead-cam engines the cam is in the head, which is far too high. Use the middle of the block, about halfway between the crank centerline and the head deck. If you can only measure the crank, use crank centerline height plus about 4–5 inches.
- Engines mounted at an angle, like a slant six or a tilted 4-cylinder: use the height of the block’s middle as installed.
- Adjust for the rest of the car: a driver sitting high, a full cage, or a battery or fuel cell up high raise the CG. Engine setback, a low seat, and a battery or fuel cell mounted low lower it.
These are only estimates. Anti-squat is calculated as a percent of CG height, so an error of 1 inch in CG height changes anti-squat by about 5–6%.