Huddie, the 4/4 is so light and the std springs so stiff the tyres have to have enough 'give' to soften the ride and get their contact patch the right shape.
I run 24 psi rears to stop the rear end squirming and 22 psi fronts - 1986 4/4.
https://sites.google.com/site/morganatica/suspension/springs-progressive-rising-rate might be interesting. Regards PJB.

4/4 2.0 Zetec SSL front and rear