Deformation is the term used to describe the amount of “give” or flex in the tyre’s casing whilst operating at the correct inflation pressure, vital to the tyre’s ability to perform as it should. A tyre forms part of the vehicle suspension system: as such, any changes made to the stiffness of the tyre will have an effect on the overall ride comfort and handling of the vehicle.
Increasing the tyre’s inflation pressure, and therefore increasing its stiffness, will give the feeling that the suspension is stiffer. Conversely, reducing the tyre pressure will increase the amount of flex in the tyre, giving the impression that the suspension is softer. However, both underinflation and overinflation have serious side-effects and in real terms a tyre should always be inflated to the car manufacturer’s specifications.
All tyres have to offer a compromise in the amount of deformation built in to the casing. A tyre designed to be used on a high performance sports car will have a much stiffer construction (as well as being lower profile) than one designed for a luxury vehicle. Tyres designed for mid-range cars, where out and out performance or luxury are not of utmost concern, will have a tyre with deformation somewhere between the two.