HadEnough wrote:
It's simple. Ignore everything except the max pressure on the tire sidewall.
Put the load on and look at the tires. The entire part of the tire that makes contact with the road (the tread profile) should be making contact. If it's bulging at the sidewall and the tread is only making contact at the edge, you are underinflated for the load. If the center of the tread profile is making contact, but the edges aren't, you have too much pressure.
Tire inflation is only a matter of getting the tire shape correct. Put as much air in as you need to get the shape correct, without exceeding the maximum pressure shown on the tire sidewall.
See these pictures for a visualization.
Well, no, judging by eye is probably the worst thing you can do. Are you really claiming that you've ever seen a tire which is making contact only at the edges (excepting one with zero pressure), or that you've seen the edges not making contact without it being vastly overinflated? There's a wide range where you have full contact, but the pressure will be wrong.
Use the manufacturer's recommendations, followed by the load tables. To figure it out independently, you need to travel a while under load, then quickly and accurately measure the tread temperature across the width, like the racers do.
