@J.Musser I'm not a member on that site, but no-one seems to have gone for the obvious "poke them with your thumb" answer - it's totally unscientific and imprecise, but you can quickly learn how your tyres should feel when correctly inflated...

@NickC Wouldn't that depend on the tire? some are rated for higher pressure. And some just have a lot more material on them. Like when someone puts 33" mud tires on his jeep, it'll feel different than regular road tires on a super duty Ford f350 truck, or a VW Jetta.

@J.Musser you are right. At best, if this method works at all, it will tell you if one tire is different from the other three. That's fairly useless if you don't know if any of the tires are properly inflated.

I think I'm going to start advising people to buy a bike pump with a built in gauge. They work,never run out of electricity and at least show you a number. Plus you get good exercise!

@BobCross I keep a pressure meter in the glove compartment of all my vehicles.