How much to pump tyres

It's a beginners question, but still ... I have some guys here at the local gas station which are telling me my tyres are ok, when I feel they are a bit soft. How much should they be inflated? What's the right way to tell? Here they measure it in what they call 'atmospheres' and so they pump tyres normally to ... say 4 atmospheres. Dunno what's wrong and what's right.

Have a look on the front door pillar near the hinges, you should find a sticker like this:-
Check your tyres at home, regularly, with one of these tools (click) - cheap for peace of mind.

Check that you have the tyres shown on the sticker then you follow the diagrams for front and rear tyre pressures based on the load you're carrying.

The pressures shown are for when the tyres are cold, ie you've not driven more than a couple of miles.

I just Googled Atmospheres, it looks like 1 Atmosphere is very nearly 1 Bar so 4 Atmospheres sounds high for tyre pressures?

wow 4 atmospheres is almost double what they should be as Missing Lincs says its roughly 1 atmosphere to a 1.0 bar of pressure.
My wifes are kept at 2.1 bar as they are the 14" tyres and its general running round town etc.
got to express that over inflated tyres are going to prematurely wear the tyres out in the centre of the tread.
So if your measuring atmospheres your static preasure at 2.1 bar should be 2.07 atmospheres or 30 psi.

No, no, no, guys! It's ok! I said '4' just as an example .... what I meant was just any number of atmospheres ... cos I was just puzzled by the difference btwn bars, PSI, and atmospheres and so on ... that's why I just said 4, when I actually should have said 'X' number of atmospheres! sorry for the confusion.

@MATTHEW LOMAX - thanks for the reply!

@Missing Lincs - The attached images show the sticker I have. As far as I see I ain't got the Michelin tyres on. Any problem with that? And another question - as far as I understand if I ain't too loaded all wheels should be at 2.1 bar and if I am heavily loaded the front should be 2.1 and the rear 2.5, right?

Make of tyre doesn't matter, it's the size. Sometimes previous owners might have changed the wheels and tyres but if the numbers match for tyre size then go with what it says on the sticker which you have correctly interpreted.

Thank you!

Oh another thing! How often should I re-inflate the tyres? I've read that for bikes they should be inflated once every month. Is it the same with cars of how often?

Frequency depends on how often you use your car and how many miles/kilometres you travel.

If the car is new to you then I'd suggest the more often the better, that way you will spot any problems like slow leaks. When you're used to the readings and happy that they are no problems then weekly for average usage and mileage is good practice. I always check tyre pressures before a long journey especially if its high speed/motorway. Always check the tyre pressures when cold, ie before you start driving or when the car has been parked for at least a couple of hours.

Your tyre pressures will vary a little as the average outside temperature changes, other than that, any significant changes are a sign of a poor pressure gauge or a tyre problem. If you're putting say 1/2 a bar pressure in weekly then you are likely loosing air from your tyre.

While checking the pressures it's a good opportunity to do a visual check. Check the sides of the tyres (walls) for scrapes, knocks, cuts, bulges or any other damage. Also look at the tread, check the depth of the groves and also that they are even across the width of the tyre. Uneven wear is a sign of something amiss with the car's alignment or possibly worn suspension parts.

Thanks a lot for your valuable input!

Missing Lincs wrote:Always check the tyre pressures when cold, ie before you start driving or when the car has been parked for at least a couple of hours.

Thanks again for the tip! I don't have a separate manometer to check my tyres when they are completely cold, so what I do is that I take the car early in the morning while it's still cool (during summers) or at any time (during winters) for a 1km ride to the nearest station and check pressure there and pump, if needed. Does that 1km journey heat up the tyres THAT much so as to get a wrong reading on the gauge at the station (and then subsequently a wrong top-up of inflation on my part)?