I bought a tyre pressure gauge today. The pressure in my car tyre should be about 30 psi, but?

Pressure gauges vary hugely in accuracy, whether they're ones you've bought or the ones on forecourt air lines. Get a decent sonic one, or a Dunlop mechanical, which are usually very accurate.

Check the other tires. If they all appear to have over 50 psi, then you may have a faulty gauge. On the other hand, if you just pumped that one - you may have put in too much. Make them all the same.

If you aren't sure about what the pressure should be - there is a sticker hidden on the inside of the door. Open the door and check the sticker, it should have the recommended air pressure and will tell you if is different front than rear.

Go to a Tesco or Sainsbury's and check your tyre pressure for free. You will then have a comparison to the gauge you have bought. The pressure marking an tyres is a maximum for that tyre. Follow the car manufacturers recommendation for tyre pressures under differing conditions. (By the way, do not treat supermarkets pressure reading as 100% true as you don't know when it was last checked).

Check in the drivers door or glove box cover for your cars recommended tyre pressure, the pressure listed on the tyre is the maximum of the tyre.

Yes it is possible you've overfilled it, the tread of the tyre is supposed to be flat if it's rounded it is over inflated.

I doubt that the gage is 60% off the calibration showing 50PSI instead of 30PSI

The guage wont be wrong, You've overdone it with the compressed air!

Let them down to 30 psi before driving as overinflated tyres will seriously affect the handling of the car and causes premature tyre wear around the middle of the tyre.

For such a simple piece of kit, gauges are surprisingly rarely wrong. Try on all your tyres, and ask a friend who knows his pressures are right to check it on his.

Let some of the air out and see if the reading changes, your tires should have a slight bulge at the bottom when properly inflated so check by deflating your tire some and see if your reading changes. then set it to the right pressure.

you may not have been holding it properly check other tyres and see result if it is 50 release air till 30 its usually wrote on the tyre the pressure needed

Buy a draper double barrelled foot pump and be done with that QVC thing you have & obtain the true results!

it should,nt pop out all the way. if it does then you have way too much air in the tires. if you want 30 lbs. then that,s the far it should pop out at.