Handling is about load: how much of the car's weight each tire carries, and how fast that changes. Every calculator here describes one part of that, and the unifying idea is that the spring is not the wheel rate and the static weight is not the dynamic load.
Spring rate is what the spring does; wheel rate is what the corner does. The motion ratio between them is squared, so a 0.7 motion ratio means the wheel only sees about half the spring's rate. Get that wrong and a "well-chosen" spring lands nowhere near the ride frequency you wanted — which is the number that actually predicts how the car will feel.
Braking moves load forward, and the amount depends on centre-of-gravity height, wheelbase and deceleration. That is why brake bias is a weight-transfer calculation rather than a fixed percentage: the harder you brake, the more the front axle can take, and the more rearward bias becomes a lockup risk.
Corner weighting is the quietest one and often the most useful. Cross-weight — one diagonal as a percentage of the total — tells you whether the car will behave the same turning left and right. At 50% it is symmetric; away from 50% it has a built-in preference, which on a track car is either a tuning tool or an unexplained handling complaint.
FAQ
Why does motion ratio get squared?
Because it affects both the displacement the spring sees and the leverage it acts through. Wheel rate equals spring rate times the motion ratio squared, so a 0.7 ratio gives roughly 0.49 of the spring rate at the wheel — a much bigger reduction than people expect.
Is 50% cross-weight always the goal?
For a car that has to turn both ways equally — most road and track cars — yes. On an oval, or where a driver strongly prefers one direction, deliberately offsetting cross-weight is a legitimate setup choice. Just know which one you are doing.