Spring rates, and what you need to consider..

Quite a few people shopping for suspensions think "I need a really high spring rate so my car handles better...stiff = better handling." Let me stop you right there. An often overlooked variable is what tires you have... Let me explain:

Tire compound and spring rate are closely related because both directly influence how a car generates and manages grip. The tire is the only point of contact with the road, and its ability to stick depends largely on compound softness—softer compounds generally provide more grip but also deflect more under load. The spring rate must be chosen to complement this behavior. If the springs are too soft relative to a sticky tire, the suspension may allow excessive body roll, pitch, or squat, which changes the tire’s contact patch and can overload the compound. Conversely, if the springs are too stiff for the grip level of the tire, the suspension won’t allow enough compliance, leading to reduced mechanical grip and a harsher, skittish ride.

In performance setups, engineers often talk about matching the spring to the tire. A softer street compound can work well with moderate spring rates, keeping the car compliant and maximizing grip over uneven pavement. On the other hand, racing slicks or extreme summer tires with much higher grip levels require stiffer springs to keep the chassis controlled and to prevent the tire from being overworked. Essentially, the more grip the tire can provide, the more spring you can run, because the tire will be able to handle and transmit the higher loads without losing traction.

Another layer of the relationship is heat and load management. Tires generate optimal grip within a certain temperature window, and spring rates influence how load is transferred across the tire surface. Too soft, and the tire may roll onto its shoulders and overheat; too stiff, and it may not generate enough consistent load, causing uneven heating and reduced traction. By pairing the correct spring rate with the chosen tire compound, the suspension ensures the tires are being used effectively—maximizing contact patch, maintaining stability, and staying in their ideal performance window.

TLDR; soft tire (200TW) + low spring rate = body roll, hard tire (all season) + high rate = loss of grip