Getting accurate tyre pressure

MinnyMinor

My car is 32 psi front and 29 rear according to manual. I got a tyre fitted recentlly on front and he put 32 but when i checked with a digital guage from aldi I found it 35.

But it was warm when he did it after driving to him, a few miles .

I checked cold before driving. Is there much of a difference between cold and hot. Which give the higher reading

And is it much problem if it is say 32.5 instead of 32 psi

voxpop

Air expands when hot - so you will have a higher reading when warm. 30-35 in your tyres wont make much of a difference - mine are 35 all round. If you are worried or the ride is a bit harsh put them all at 32.

MinnyMinor

voxpop wrote: »

Air expands when hot - so you will have a higher reading when warm. 30-35 in your tyres wont make much of a difference - mine are 35 all round. If you are worried or the ride is a bit harsh put them all at 32.

want them as near as poss to manual level to have even wear

woody33

I have a digital gauge from Tesco and tend to trust it, but not for any good reason. I even trust it more than the gauge at Tesco's filling station. So anyway, read your pressure at home and then check again with your gauge at your local filling station, you will probably find the pressure has gone up 3 or 4 psi. You should then take a reading from the filling station gauge and see what the difference is. In the unlikely event of the two gauges matching, use the garage air to put in 3 or 4 extra psi to allow for the warmer tyres. If the garage gauge is a few psi out, allow for that. (Then if you are like me you start to worry about all the air lost in little hisses when you repeatedly test the tyres....). I run my tyres a few psi over recommended for reasons of handling and economy, but probably best to do it by the book.

Esel

woody33 wrote: »

I have a digital gauge from Tesco and tend to trust it, but not for any good reason. I even trust it more than the gauge at Tesco's filling station. So anyway, read your pressure at home and then check again with your gauge at your local filling station, you will probably find the pressure has gone up 3 or 4 psi. You should then take a reading from the filling station gauge and see what the difference is. In the unlikely event of the two gauges matching, use the garage air to put in 3 or 4 extra psi to allow for the warmer tyres. If the garage gauge is a few psi out, allow for that. (Then if you are like me you start to worry about all the air lost in little hisses when you repeatedly test the tyres....). I run my tyres a few psi over recommended for reasons of handling and economy, but probably best to do it by the book.

Can't see your logic in the bolded sentence?

DublinDilbert

This is why in certain applications they use nitrogen as opposed to just air. Its the oxygen in the air that expands/contracts at different temperatures, nitrogen is much more stable.

Either way any tire pressure gauge will be +/- 10% accurate if your lucky.

A few PSI (eg 5 PSI) will make feck all difference.

batman2000

DublinDilbert wrote: »

A few PSI (eg 5 PSI) will make feck all difference.

Depends on the profile of the tyres, 5psi is plenty. I notice if there was a 5psi increase/ decrease in my tyres

doctorchopper

unless your pressure gauge has been calibrated its hard to say what pressure you are putting into it. I agree with the statement of using nitrogen, a lot of the tyre fitting places in north america have switched to nitrogen for that reason

mickdw

I run my tyres towards the lower end of acceptable pressures and tbh I can feel a couple of pounds either way from where I like them in the front tyres at least. I can instantly feel it on entry to bends.

beetlefan

Most pressure gauges at petrol stations are way out and are never calibrated as they should be at least once a year. If you ask in the petrol station if the pressure gauge has been checked or calibrated recently they will look at you like you have just landed from Mars.
We are paying enough for fuel and we should demand proper services from the service station.

doctorchopper

beetlefan wrote: »

Most pressure gauges at petrol stations are way out and are never calibrated as they should be at least once a year. If you ask in the petrol station if the pressure gauge has been checked or calibrated recently they will look at you like you have just landed from Mars.
We are paying enough for fuel and we should demand proper services from the service station.

Exactly, try asking them what octane rating their fuel is