Old Handbook tyre pressures

[Knap]

Tyres radial 155x14 or 165x14 on 4J / 5J or 4.5 wires
Pressure 22F24R add 6psi for sustained over 90mph and 2psi for loaded boot.
Vehicle weight 1312Kg 50;50F/R RWD
Due to tyre availability most owners use 175 or 185 on original wheels or 195x60x15 Load index 88 on 5.5J or 205x65x15 on 6J or 205x50x17 on 7J

Should the handbook pressures be revised?

 

[CapriRacer]

There has been several rounds of rethinking tire pressures over the years. Usually this takes place in committe meetings at vehicle manufacturers with urging of the tire manufacturers. I'm not sure how many times there have been increases in tire load capacity (size and pressure), but it is obvious it has been more than twice.

So an old handbook doesn't benefit from the learning that has taken place.

For one, there have been cases where the tire bead has unseated in cornering, so now there is a minimum inflation pressure that is used. There isn't complete agreement as to what that value is, but I prefer the higher value - 26 psi.

This also satisfies my need to increase the tire load capacity.

Hope this helps.