Tyre pressure advise please

[enuff_zed]

I found this interesting test
He does a pretty good job of testing. Its crazy that 2 identical units from the same manufacturer can read so differently. And some are so far off the mark.
When we are talking about differences between 32, 34, 36 psi I'm not sure if I have confidence in these gauges to be that accurate. One of the worst offenders was apparently 9psi too low.

At the end of the day, you should always use the same gauge and adjust the pressures to ones that make the car handle properly, without adverse wear to the tyre. Doesn't matter if it reads 30, 40 or 50psi. If the number it shows makes your car handle properly and you always set to that number then what it actually reads is immaterial. That's basically the premise that the pressure monitoring system works on. It accepts whatever you tell it is the datum, then only looks for changes, not actual figures.

 

[Pondy]

What do you reckon the contact patch with the ground is? Conservative estimate? 20 square inches? Thats an extra 40 pounds applied.

I dunno but modern wide tyres are designed to sit pretty 'flat' on the contact patch. It wasn't too long ago that you couldn't stand a removed tyre on it's own without it falling over. Now they will sit there forever even in a significant breeze.

Due to the flat design and the strengthening cords to make them so, I find it difficult to believe that 2 psi difference can alter the 'flatness' by much at all. I could understand over-inflating by 30% would do it but not 6%.

 

[enuff_zed]

I dunno but modern wide tyres are designed to sit pretty 'flat' on the contact patch. It wasn't too long ago that you couldn't stand a removed tyre on it's own without it falling over. Now they will sit there forever even in a significant breeze.

Due to the flat design and the strengthening cords to make them so, I find it difficult to believe that 2 psi difference can alter the 'flatness' by much at all. I could understand over-inflating by 30% would do it but not 6%.

So if I increased the pressure by 2psi, you'd expect no change. If I increased it by another 2psi you'd expect no change.
If I did that 5 times, you'd expect no change each time, but at the end of it I have increased the pressure by 30%.

 

[Pondy]

So if I increased the pressure by 2psi, you'd expect no change. If I increased it by another 2psi you'd expect no change.
If I did that 5 times, you'd expect no change each time, but at the end of it I have increased the pressure by 30%.

Don't be silly! That's my job.

 

[Gebbly]

Well in the interests of science (and because my mum has been pestering me for what I would like for Christmas), based on the linked video and a couple of others with people testing side by side comparisons I have ordered this Jaco gauge and asked my parents for the much cheaper Etenwolf, to go in the glovebox. When I have my hands on them I will see how they compare with my tyre inflator and current gauge (both cheapos from halfords years ago) which I keep in the other car.

 

[MrPT]

I'd second the recommendation to just use one gauge/compressor (unless you want to invest in something pricey and get it calibrated every year). I found a 3-4 psi spread across my cheap gauges and none of them were correct when compared with garage kit (assuming that was accurate, which it may not have been).

[EDIT - aha, I see you have decided to "go big". TBH, £50 is not an unreasonable amount of money to spend if you want peace of mind.]

You could also try switching between 30/30 and 36/36, back-to-back, just to dial yourself into the differences.

 

[MikeyH]

Will do. When I took the pressures before pumping them up they were down a little (the fronts were about 28-29psi). I had noticed it would sometimes tramline as @Rockhopper suggests. So perhaps now the pressures are up a bit it will stop that tramlining.

Mine does at those pressures