[BonzoHansen]

Taken from How To Make Your Car Handle by Fred Puhn

To Reduce Understeer:
Increase weight transfer at rear by increasing rear roll stiffness
Reduce weight transfer on front by reducing front roll stiffness
Reduce front toe-in
Increase aero downforce on front tires
Reduce aero downforce on rear tires
Wider front tires

To Reduce Oversteer:
Reduce weight transfer at rear by reducing rear roll stiffness
Increase weight transfer on front by increasing front roll stiffness
Increase front toe-in
Reduce aero downforce on front tires
Increase aero downforce on rear tires
Wider rear tires

He states the old rule of thumb was to increase front PSI to reduce understeer and increase rear PSI to reduce oversteer. He goes on to say this really applies to road cars where PSI is often too low to begin with. Best bet is to get PSI correct via temp readings via skidpad testing and changing psi only limits grip.

In Herb Adam's Chassis Engineering, he also does not appear to get into PSI other than working off temperatures to get to ideal and is generally in the same vein as Puhn.

So that jives with my gut that PSI is just fine tuning and Puhn talking about only going up on road tires matches my experiences.