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Author Topic: Tyre pressures on the sunny side  (Read 1921 times)

KADE

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Tyre pressures on the sunny side
« on: April 06, 2021, 11:51:06 AM »

I checked the tyres on my other car  (YETI) today. I noticed that there was at least 7PSI difference from one side to the other.  One side of the car is in direct sun the other in shade.  My trusty Aldi infra red thermometer revealed that the shady tryres were at 10 degrees while the sunny side had a surface temp of 34 degrees. I guess most people are aware to check the tyres before a long run but it did surprise me that a ray of sunshine on a cold winter morning to have such a significant effect.

Malcolm.
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Peter Holden

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Re: Tyre pressures on the sunny side
« Reply #1 on: April 06, 2021, 12:55:24 PM »

It used to be recommended that tyres were checked first thing in the morning.

Peter
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Clifford Pope

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Re: Tyre pressures on the sunny side
« Reply #2 on: April 06, 2021, 02:04:07 PM »

It used to be recommended that tyres were checked first thing in the morning.

Peter

That would be when they are at their coldest, after say a long cold night and a frost. How much would the pressure rise when at running temperature?
I'd have assumed the recommended pressures were supposed to be at average running temperatures with average sun ?
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Wittsend

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Re: Tyre pressures on the sunny side
« Reply #3 on: April 06, 2021, 02:05:10 PM »

Quite so - still recommended, tyres will be cool and not yet heated up by the sun.
Best time to check the pressure, early in the morning - if the car is left out all night.

I have a 3rd party tyre monitoring system on my modern car.
Displays pressure & temp all the time.
When the car has been standing there can be a difference from one side to the other.
Once you are moving and got a bit of "heat" into the tyres the temps will balance out, and the pressures to be within a couple of psi of each other on the same axle.
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Genem

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Re: Tyre pressures on the sunny side
« Reply #4 on: April 06, 2021, 03:29:13 PM »

  One side of the car is in direct sun the other in shade.  My trusty Aldi infra red thermometer revealed that the shady tryres were at 10 degrees while the sunny side had a surface temp of 34 degrees.

Lucky ! As I type, its currently snowing outside, I went to wash the mud off Tonka and can't, the garden hose is frozen !

So much for "Spring weather" I suppose !
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ChrisJC

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Re: Tyre pressures on the sunny side
« Reply #5 on: April 06, 2021, 03:37:38 PM »

I checked the tyres on my other car  (YETI) today. I noticed that there was at least 7PSI difference from one side to the other.  One side of the car is in direct sun the other in shade.  My trusty Aldi infra red thermometer revealed that the shady tryres were at 10 degrees while the sunny side had a surface temp of 34 degrees. I guess most people are aware to check the tyres before a long run but it did surprise me that a ray of sunshine on a cold winter morning to have such a significant effect.

Malcolm.

I would be highly surprised if that was solely due to temperature.

Gay-Lussac's law states that (assuming constant volume) pressure is proportional to temperature.

Your two temperatures in Kelvin are 283 and 307 degrees.

Assuming the hot side was at 35PSI, then the cold side would have been at 32PSI, only accounting for 3PSI of the difference.

But it does make a mockery of trying to set your tyre pressures overly accurately as they will change anyway!

Chris.
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Wittsend

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Re: Tyre pressures on the sunny side
« Reply #6 on: April 06, 2021, 05:02:24 PM »

.... but at least you are checking the pressures.

I understand that a lot of "motorists" are driving round with under inflated tyres, even allowing for temperature effects.

People just don't seem to bother checking their tyres any more.
I've never seem my neighbours checking their tyres - maybe they do it at the petrol station.
But then I believe that "AIR" is no longer free  :shakeinghead and the gauge(s) are not that accurate.

I guess that's why new cars now come with TPM (tyre pressure monitoring).
(Just wait for the tyre fitters to *&%^$ up one of the valve stem sensors  :shakeinghead
The TPM systems I've seen don't tell you which tyre is down - making you check all them. The system I have tells you which tyre is down - prudent motorists will be checking all their wheels. Some systems even monitor the spare. Endless fun scrolling down the menus to reset the high & low pressure levels.)

Ours are not F1 racing cars so a couple of psi either way is not a great worry.
The main thing is not to be running round on flat tyres.


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oilstain

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Re: Tyre pressures on the sunny side
« Reply #7 on: April 06, 2021, 05:45:27 PM »

ATS always try to get you to pay to fill your tyres with Nitrogen-
https://www.atseuromaster.co.uk/consumer/tyres/tyre-services/nitrogen-inflation
does this gas avoid/reduce this problem ???
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ChrisJC

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Re: Tyre pressures on the sunny side
« Reply #8 on: April 06, 2021, 06:57:22 PM »

ATS always try to get you to pay to fill your tyres with Nitrogen-
https://www.atseuromaster.co.uk/consumer/tyres/tyre-services/nitrogen-inflation
does this gas avoid/reduce this problem ???

Given that air is 78% Nitrogen, I fail to see what having 100% Nitrogen will do apart from lighten your wallet more than necessary.

Chris.
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Wittsend

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Re: Tyre pressures on the sunny side
« Reply #9 on: April 06, 2021, 07:09:57 PM »

There is a good advantage in using Nitrogen to fill your tyres.
The gas is inert and doesn't react with the rubber and permeate through the tyre wall/inner tube. In other words, your tyre pressures should remain stable for longer. They will still be affected by temperature.

Aircraft tyres are filled with nitrogen, as are racing cars.

It's probably a finesse not needed on Series Land Rovers.

(You can Google N2 for tyre filling)

I believe racing cycle teams filled their bike tyres with helium - as brinkmanship more than anything.
Helium is very light and leaky so not perhaps the best choice for a long event, but for sprint races ???


 
 
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ChrisJC

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Re: Tyre pressures on the sunny side
« Reply #10 on: April 06, 2021, 08:52:25 PM »

This article gives some good reasons to use nitrogen in aircraft tyres:
https://en.wikipedia.org/wiki/Aircraft_tire
Not justification for use on a road car though.

In my experience, wheels with tubes in remain inflated for at least a decade.
Tubeless tyres inevitably go down slowly. I rather suspect the sealing against the rim is imperfect.

Chris.
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Clifford Pope

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Re: Tyre pressures on the sunny side
« Reply #11 on: April 06, 2021, 09:03:35 PM »



In my experience, wheels with tubes in remain inflated for at least a decade.


I'd agree. I've had a pile of old wheels with the worn out tyres on, stacked in a corner, for about 25 years. Recently I wanted one of them as a temporary prop while swapping wheels around and found it was still appparently fully inflated.
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Peter Holden

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Re: Tyre pressures on the sunny side
« Reply #12 on: April 06, 2021, 09:44:18 PM »

Some folk are not fit to be let loose with a car.

It makes you realise that the drivers test should have another part

Peter
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