Springs & wheel rate

What a spring actually controls

A spring is the part of the suspension that resists the wheel moving up into the car. Its job is to control how much the car's platform — the body, and with it the floor and wing — moves when load is thrown at it. And load is thrown at it constantly: the front dives under braking, the body rolls onto the outside wheels in a corner, and the whole car squashes toward the ground as aerodynamic downforce builds with speed.

So the spring is not really about comfort. It decides how far the car settles under each of those loads, and therefore where the floor and wing end up sitting relative to the track. Get the springs wrong and every other lever you tune is sitting on a platform that won't hold still.

Spring rate, motion ratio & wheel rate

Spring rate is the stiffness of the spring itself — how much force it takes to compress it by a given amount. But the spring rarely pushes straight up and down on the wheel; it sits at an angle and on a lever, so the wheel and the spring move by different amounts. That relationship is the motion ratio: simply put, how far the spring moves for a given movement of the wheel.

What the tyre actually feels is the wheel rate — the effective stiffness measured at the contact patch. And because of that lever, it doesn't scale one-to-one with the spring:

This is exactly why guessing from the spring number alone is a trap, and why the engineers work from wheel rate read in context — what the tyre is doing in each phase of each corner — rather than the raw figure on the setup screen.

Stiffer or softer — the trade-off

There is no "best" stiffness, only a trade-off — and knowing which way to move it is the whole skill. Two ends of the same dial:

• Stiffer — less body movement, sharper and more immediate response, and a steadier aero platform (the floor and wing barely move, so downforce stays consistent). The cost: less mechanical grip over bumps and kerbs and on low-grip surfaces, because the tyre struggles to follow the road.
• Softer — more mechanical grip and compliance, the tyre tracks the surface and stays loaded over bumps. The cost: more pitch and roll, slower response, and a platform that moves — so the aero balance shifts around as the body works.

We don't publish a stiffness recipe, because the right answer is specific to your car, track and corner — which is precisely what the engineers compute from your telemetry rather than read off a chart.

Front vs rear split & the couplings

Springs aren't one number — the front-to-rear split sets how the car pitches. A relatively stiffer front resists braking dive and can make turn-in feel sharper but edgier; a relatively stiffer rear resists squat under power and can free rotation or, taken too far, unsettle the rear. So springs are part of the car's mechanical balance — the slow-corner balance set by springs, anti-roll bars and the differential — not just a ride-quality setting.

Two couplings matter more than anything else, and they decide the order you work in:

• Springs feed the aero platform. How far the car settles sets its ride height and rake (rear higher than front) — and that places the aerodynamic load. Change the springs and you've moved the aero platform, which is why springs come before the fine aero work, not after.
• Springs set the energy; dampers control the rate. The spring decides how far the platform moves and stores that energy. The dampers then control how fast that movement happens and how the energy is released — shaping the transient phases of a corner. You set springs first, dampers last.

Reading the symptoms — not guessing

You don't change springs because a forum post said so. You change them because of what the car is doing, and where. At a conceptual level, two classic patterns:

• Lazy or floaty, vague platform, lots of body movement, slow to respond — often a sign the springs are too soft for the load the car is carrying.
• Skating and won't put the power down on bumps or a rough surface, rattling across kerbs, nervous over the smallest input — often a sign the springs are too stiff, and the tyre can't follow the road.

But "often" is doing a lot of work in those sentences — the real fix depends on which axle, which corner and which phase. That's the difference between a hunch and engineering: SimRace.app reads your whole setup and the engineers log the telemetry corner by corner to pin the symptom to a cause, then give you the moves one change at a time, in the right order. The science stops being a black box, and you stop guessing.

FAQ

The setup glossary

Springs are one lever in the suspension. Read the rest of the glossary to see how they fit together — and tune in the right order:

• Dampers: bump & rebound
• Bump stops & packers
• Ride height & rake
• Anti-roll bars
• Camber, toe & caster
• Mechanical balance
• The full setup guide →