Every so often someone asks advice on tyre pressures and I have tried several variations over the 6 plus years during which I have owned the Plus 4.

During that time there have been several changes in the suspension configuration and a change of tyres. Interestingly the changes in suspension configuration seemed to also have an influence on what seemed to be optimal tyre pressures. Quite naturally the change of tyres also had an effect.

With the original factory supplied Yokohama 195/60 R15 tyres and I found 1.5 Bar (22 psi) does not feel good. No doubt the car grips well at that pressure but it feels as though the tyres are under-inflated and a bit squirmy in corners.

I now have Michelin CrossClimate 195/65 R15 tyres fitted. They may not be optimal in summer on hot dry roads but they are quite acceptable, fantastic on wet roads and good in snowy conditions. In part they are fitted because in this area you must have snow tyres or carry chains from 15 November to 15 April.
I currently run 1.6 bar (23 psi) front and 1.7 bar (25 psi) rear.

My findings, in general terms with different pressures are as follows:
1.5 Bar (22 psi) - comfortable ride, particularly on rough roads, slightly heavier steering and the feeling that the rear is slightly under-inflated (depends on the make and model of tyre
1.6 bar (23 psi) - a reasonable compromise between comfort and general feel.
1.7 bar (25 psi) - the car feels better planted on the road and the perception of body roll is reduced.
1.8 bar (26 psi) - great on smooth surfaces but feels harsh over minor bumps or a broken road surface. Steering is lighter.

I think it is very much a matter of personal choice and how the car feels with different tyres and pressures. With such a light car small changes can make a big difference. Too high a pressure definitely makes the ride harsher and too low a pressure may make for a feeling of underinflation in cornering.

Peter

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