My cars all had this info under the gas cap. With details about number of people/load/comfort/economy.

You should also know that normal driving will raise the temperature and therefore the pressure of your tires. This means if you've been driving for a while and set your your pressure to exactly what that placard says, you're most likely going to have low pressure the next morning. Tire pressure should be set when cold. If that's not possible, add about 4 psi more when you're at the pump. The next morning you can use any cheap pressure gauge to check and let some air out to correct if necessary.

I went to a car show today and noticed a lot of text on the frame of a Lamborghini Aventador. I wondered what that was. Now I know.

This is one of my pet peaves. I work at a fire department and I can't tell you how many times I catch the new guy airing the tires to like a billion psi because that's what it said on the sidewall. EVERYTHING HAS A TIRE PLACARD, the sidewall is the max for the tire, if the placard says more than the sidewall says then you have the wrong tires.

I was driving the other week and my low tire pressure light went on. I opened the error page in the infotainment screen and sure enough it said "low tire pressure".

I went to measure it and it was actually high tire pressure due to the hot weather. I let out some pressure and it went away.

So YSK that apparently cars will falsely report high tire pressure as "low" tire pressure and to always measure it before going to fill up.

It isn’t always on the drivers side. It can be on the passenger side, sometimes front, sometimes rear… sometimes they put it in the glovebox - depends on the car manufacturer.

Source: used to work in tire shop.

So many people incorrectly think they should go by the number on the tire, not knowing that that number is the max that tire can hold, not the recommended pressure. Putting the max amount in prevents the tread from contacting the road flat, which will cause the middle of the tread to wear quicker than the rest. Same for too little pressure, but in this case the edges wear quicker than the middle. Using the recommended pressure for your vehicle ensures the tread is contacting the road evenly all the way across the width of the tread, and gets you the best gas mileage and treat wear.

Also if your car is German and the country you're in is not, you may find yourself in a situation where your car is bitching about tyre pressure but the only pump you can find at a petrol station is in PSI and the label is in Bar, and the only way you can convert those is to desperately wave your phone around like a madman trying to get some working internet while freezing cold in the rain. You might be well served by doing that conversion up front and writing it down somewhere.

Totally hypothetical situation, of course.

"Cold pressure". If you've driven the car, as you would to go get the tire pressure checked, the tires are no longer cold and you need to add 4 lbs to the pressure listed.

This is just plain wrong!!1!1! You should always fill it to 100! Its 100% or nothing when it comes to tires.

(/s obviously)

Also be aware many spare tires (those thinner ones you find in the car) have larger pressure

Does anybody adjust the tyre pressure due to weight in the car? Surely driving with larger weight in the boot would require a difficult psi/bar for the tyres?

Edit: great ysk post!