Glossary
Centre of Gravity Height: How to Measure It and Why It Sets Grip
The centre of gravity (CG) height is the vertical position of the point where the car's whole mass can be considered to act. Together with track width it fixes total lateral load transfer in a corner: load transfer = lateral acceleration × weight × CG height ÷ track width. Because tyres give less grip per unit load as load rises, a lower CG means more total grip. Race cars range from about 250 mm (formula cars) to over 500 mm (production-based cars).
| Car type | CG height | Track width | Comment |
|---|---|---|---|
| Formula car | 250–300 mm | 1,400–1,600 mm | Driver lying down, low engine |
| Sports prototype | 280–350 mm | 1,600–1,700 mm | Wide track aids ratio |
| GT3 | 400–450 mm | 1,650–1,700 mm | Dry-sumped, low seat |
| Touring / production | 450–550 mm | 1,500–1,650 mm | Limited by road car structure |
| Speedway sedan | 500–600 mm | 1,600–1,750 mm | High ride height on dirt |
Measuring CG height
Weigh the car level on four scales to get the total weight and the front/rear split. Then raise the rear (or front) by a known height on blocks, keeping the car on scales, and record the new front weight. The weight shift, the lift angle and the wheelbase give the CG height above the wheel centres via trigonometry; add the wheel centre height to get it above ground. Lock the suspension solid or the movement corrupts the result.
Lowering the CG
Mount heavy items low: battery, fire system, ballast, fuel. Lower the seat and driver. Lower the ride height within what the geometry and aero allow. Every 10 mm of CG height on a 1,600 mm track car changes load transfer by about 0.6% of weight per g of cornering, which is measurable at the stopwatch.
Frequently asked questions
Why does CG height matter if total weight stays the same?
Because tyre grip is non-linear with load. Transferring load from the inside to the outside tyre loses more grip on the inside than it gains on the outside, so less transfer means more total grip.
How accurate does the measurement need to be?
Within 10–20 mm is useful for setup calculations. A lift of at least 15–20° and locked suspension are needed for that accuracy.
Does fuel load change CG height?
Yes, if the tank is high or low relative to the CG. Measure with half tanks for an average, or at both extremes if the car is very fuel-sensitive.
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