Wheel rate is the spring stiffness the tire actually feels after the suspension's leverage — spring rate times motion ratio squared. A 400 lb/in spring at a 0.7 motion ratio delivers about 196 lb/in at the wheel.
Motion ratio is the part racers get wrong. Penske Racing Shocks defines it as “the ratio of spring displacement to wheel displacement” and gives wheel rate as WR = k × MR². Mount the spring right at the wheel and that ratio sits near one; move it inboard and the spring travels less than the tire does, so the ratio drops. The exponent is what catches people. Penske: the ratio “is squared because leverage affects both how far the spring moves and how much force transmits back through the suspension.” Forget to square it and you overestimate the tire’s rate. Measure the ratio on your own car — coil-over, coil-on-shock and bellcrank layouts are not the same — and compare setups in wheel rate, not in spring rate.
Two cars running the same spring on the bench can feel completely different at the tire, so wheel rate is the only honest way to compare one setup to another.