Lars

No answer is the right one, as you have to specify what tyre you are talking about. If we are talking normal radial road legal tyre ( Like standard tyre original mounted on a new Impreza)
Higher pressure = more grip
Lower pressure = less grip

This is only valid up to around 38-40 PSI and I'm not sure what grip you have with 0 PSI.

Lars

Sorry I forgot your question 2
Start out with 4-6 PSI more than Subaru specify as standard.
The rest is up to you, as it is related to your driving style, and the set-up of your car. For this reason you will find people claiming that 38-32 is the best and other run 35-35. I'm sure they are all right, but their cars have different set-up, and they use different driving technic.
I hope this will help you. There is only one way to find your own pressure. Join a track day and start playing with the pressure.
Lars

TRIGGER

Sorry to revisit an often mentioned thread, but having searched the last 18 months of messages I am totally confused.

Can I please get a definitive answer to the following questions:
1) Does reducing pressure increase or decrease grip ? (i.e lower rear pressure gives more oversteer or less ?)

2) for the Type RA I have on 16" rims what pressure should I run for the track ? (bearing in mind the rear bias of the car).

Sorry to be boring but really appreciate yr help.