dave said:i was told today by a dude that has good rep that rule of the thumb is 2lb/in(squared) extra for each inch bigger
thats what i always told people until i went to this place, its most advance tyre fitters ive ever seen in my life seemed to know thier stuff, there was top motors in there inc 1 of them lhd lancias mmm. i would think they would soon go out of business if all thier customers tyres started to whear oput in the middle too quickfixitagaintomorrow said:I'm not sure about this.
The PSI figure is exactly that, pounds per square inch. If you put wider tyres on - say 205 instead of 185 then you have far more rubber in contact with the road.
The weight of the car will be spread out more across the tyre, so the mathematical part of my head suggests a very slightly lower psi figure for wider tyres.
The diameter should make no difference at all, it's the size of the footprint that matters.