Safe Speed Forums

How much difference does ambient air temperature make to tyre pressure?

If one inflates their tyres to the correct pressure on a cold day such as today, does the tyre warm up enough to over inflate them under motorway driving conditions?

Is it taken into account when tyre pressures are determined?

Does it matter?

TIA

Yes it makes a difference. My car is usually parked sideways-on to the sun. The two tyres on the "sunny side" are usually half a PSI more than the ones on the shady side (as accurately as my cheapo gauge can measure)!

Yes it's taken into account when determining tyre pressures (within reason)! I guess that if you inflated them to the correct pressure in the Antarctic and then air-lifted the car to Death Valley and took it for a fast run, you'd have problems, but for most normal running there wouldn't be. Manufacturers tell you not to check your tyre rpessures after a long run at high speed - that usually puts them up a few PSI but they have huge safety factors. It's also self-limiting, up to a point. A soft tyre generates more heat because of sidewall flexing, so if they end up being slightly over-inflated at high speed, that would help reduce the flexing, thus the temperature, and the pressure.

For interest, what is the accuracy of the average owners / garage gauge expected to be . Not being pedantic or funny, but could the expected accuracy and the possibility the frequency of checks on commercial forecourt ones be one reason for the sudden increase in tyre pressure machine chargers .( or something else for petrol stations to milk ).Would expect that in this day and age that forecourt gauges would be subject to TSA checks - ( if for no other reason than that they exist)

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

I believe that a few years ago forecourt airlines were brought under the aegis of Trading Standards who insisted that the gauges be accurate. That was when the garages started charging, presumably to cover the fees charged by TS. I find it more convenient to have my own compressor and gauge

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

Given the wide range of recommended presures dependent on anticipated speed, loading etc, I dont imagine in most cases that the "correct" tyre pressure is anything of an exact science anyway.

On my (rather heavily loaded) van I have the rear tyres up at the maximum (65) and the fronts at 55, both these are somewhat higher than the handbook recommendations but if I set them at the "recommended" presures they look flatter than a cowpat from a very tall cow and the steering becomes almost impossibly heavy!

I have done over 270,000 miles like this without issue!

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"The road to a police state is paved with public safety legislation"

So do I , as the charges are now on average 50p - whether or not you need to adjust the pressure .

_________________
lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

Those plastic bike stirrup pumps fit and go up to 80psi. They pump quickly too.

Yes, I have one of those; a Joe Blow thingy. I find them really good, certainly better than those crappie twin-tub foot pumps, and they make me feel like I’m on one of those pump action mine carts.

If we are pedantic, the tyre pressures should be adjusted to the load and number of passengers but no-one ever bothers and in the real world it probably doesn’t matter anyway.

I’m supposed to put an extra 6 psi in the back tyre of my motorbike when I take a passenger but since 99% of my riding is solo I don’t bother and it doesn’t feel dangerously different either way.

billyfat

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

Er, this is probably quite a sad thing to admit, but, I, er, DO actually put the pressures up a bit if I'm doing a long run with the family compared to my one-up motoring! Mainly for fuel consumption reasons though.

Oh I would in your situation Mole or if I have my honeybunchkins on the back for a long jaunt but if we’re just nipping out fairly locally I don’t bother. She’s only a size 6 anyway; I’ve seen more meat on a butcher’s apron.

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.