If I recall correctly Trading Standards used to go round air lines at Garages to certify their correctness.

So check with a cerified outlet into your tyre and then use your purchased guage....

dvd

Thanks - the posts are VERY helpful. I'll now look to spend some Christmas money ! Excellent tip re loss of air pressure. Thanks again

Had a dial type gauge for 20 years or so now. Was expensive at the time but when I have checked it against other similar gauges (not recently) it has always been spot on. Also have a couple of pen type gauges, considering how cheap they were these are pretty close to the dial type gauge, probably more robust but I find that in certain valve positions and valve types it can be hit and miss getting a reading.

Gauges on footpumps are typically rubbish and I have never had any luck whatsoever with electric pumps, if you run them too long they simply burn out the motor.

Thanks for these valuable posts. I will buy after Christmas now. When knowledge is shared on this forum it is very impressive.

Happy Christmas all and may the New Year bring all you wish yourselves.

I had a years old dial guage that finally packed up. I would take the pressure and the needle would 'sink' after disconnecting insated of remaining in situe.

I bought one of these for under £4 delivered,

www.dx.com/p/1-lcd-digital-tire-pressure-gauge-yel...3

it is accurate to the shiny new digital one in a SAINSBURY'S station and that's good enough for me, built in light and illuminated display too. God bless the Chinese.

Edited by Hamsafar on 24/12/2014 at 17:31

I have a few digital tyre pressure gauges and they are all accurate. An RAC one, A professional one from MAC tools and a cheap £2 one from Tesco at Gallows corner.

Some years ago I had a sykes pickavant dial type one that was pretty good until someone used it on a tyre that had a pressure higher than it was designed to read and it never returned to zero after that.

I would never buy that Michelin one - The price is far too much.

The observation that actual pressure within a tyre depends very much on the tyre's temperature.[and the ambient temp, for that matter]....is an important one.

That is why manufacturers always quote cold pressures.

<< That is why manufacturers always quote cold pressures. >>

Quite so, but there is 'cold' and 'colder'. Just now, with outside temps a little above freezing, an inflated tyre will read several psi lower than the same tyre in midsummer. Even as a trained scientist I am still a little surprised by the noticeable pressure drop when the weather turns colder - when the absolute temperature may have dropped by 8°, or only 3%.

And as a trained scientist, you'll realise that the apparent tyre pressure shown on a tyre gauge is the pressure ABOVE ambient air pressure.

It's measuring and maintaining the differential that's important - easier to accept scientifically if the word "cold" is replaced by "ambient".

Can anyone suggest what kind of percentage variation there can be to a maker's recommended running pressure before there is a perceptible change in driving characteristics? This obviously depends on many mechanical factors to do with the tyre's and the car's construction, but equally obviously there are lots of cars out there running with significantly under-inflated tyres?

From experimentation, only a couple of psi difference is needed to start noticing differences - particularly in front:rear balance - but like many things it depends on your level of mechanical empathy, real or imaginary!

My SUV has recommended pressures of 33:33 - it handles more to my taste at 36:33 with less understeer but the ride is noticeably harsher particularly in winter when the sidewalls are stiffer due to lower temperatures - tyre wear across the treads is more even at 34:32.

So I tend to run 33:33 in winter and 36:33 in summer.

Edited by RT on 27/12/2014 at 10:30