Spring rate
The stiffness of the corner springs. Stiffer springs tend to hold ride heights more constant between low and high load, which favours aerodynamic consistency and platform control; softer springs tend to let the tire follow the road better, which favours mechanical grip — especially over bumps and kerbs. Spring changes alter both pitch and roll stiffness, so they interact directly with anti-roll bars and with the static heights the perches set. Match stiffness to the track surface and re-check the balance in both slow and fast corners.
Effect by corner phase
Stiffer springs resist pitch under braking, keeping the aero platform steadier but transferring load to the tire faster.
The front/rear stiffness split contributes to roll balance: a relatively stiffer end tends to give up lateral grip first.
Softer rear springs tend to help traction out of slow corners, particularly on rough surfaces.
Symptom tendencies
These describe tendencies, not rules.
Loss of grip over bumps or kerbs
Softer springs at the affected end tend to recover mechanical grip at some cost in platform control.
High-speed understeer combined with low-speed oversteer Mid-corner
A stiffer rear spring with matched static heights can move the two ends of the speed range in opposite directions — a classic combined fix worth testing as one deliberate experiment.
Exit oversteer — the rear lets go when the power comes in Exit
Softer rear springs tend to keep the driven axle loaded and more progressive on power. Re-check the fast corners too: the same change moves the aero platform, so the fix can read differently at speed.
Verify on track before you commit to a change.