Increase in Tyre Pressures (1 Viewer)

Zigisla

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Not with standing the fact that I run at 80 psi - not weighed yet and seems like Continental will say 80 anyway; but when on a longish run my tyre pal indicates that my pressures have increased to between 88 & 90 psi and sets off the warning buzzer - 10% according to the instructions I believe.
Is this increase normal and the warning should be set higher, or do they seem to be increasing too much at a higher than normal px and needs investigating? This is all 4 tyres rising in px and not just 1, no warning of over temping and as yet not thought about dropping the px yet.
Experience and words of advice welcome as always.
 
Nov 6, 2013
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I had exactly the same result and was surprised to see the pressure increase by 10lb or more:Eeek:
I found that the warmer the weather the higher the increase. I have just set my tyrepal alert higher.
 
Oct 8, 2014
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My tyre pressures typically rise by less than 10 psi, as indicated on my Tyre-Pal. The only time the alarm has gone off was in July last year, on the hottest day of the year, when pressures and temperature rose considerably as we came down the M1. We pulled into a Service area and waited a few hours for cooler weather.

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Kevan

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I have snooper tyrepilot. tyres are rears 80 psi front 70 psi usually goes up to about 10 psi when hot just set alarm to a bit higher am told this is quite normal.
 
Nov 25, 2014
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I had the same issue and contacted tyrepal who advised increasing the upper limit.

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mikebeaches

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Yes, I was surprised just how much the tyre temperature readings increased on the van when travelling at speed, especially when in the Mediterranean region with high ambient temps.

Believe it is absolutely normal, so you can adjust your Tyrepal alarm levels accordingly.
 
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Zigisla

Zigisla

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If you look up "Boyle's Law" you will find out why your tyre pressures go up when driving. This law is the sole reason a diesel engine works.

D.
Aware they would go up, but it was the amount they went up concerned me though
if the volume of the air inside remains constant and doesn't decrease why does pressure increase.

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2657

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If you drive for long periods with the hot sun on one side of vehicle then one side will be higher than the other as well:)
 
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Zigisla

Zigisla

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Look up Boyle's law, that will explain all.

D.
No it doesn't. unless I am failing to see how the volume of the air decreases as you drive along. It also does not explain why pressure increase by approx 10 psi.

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Gorse Hill

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No it doesn't. unless I am failing to see how the volume of the air decreases as you drive along. It also does not explain why pressure increase by approx 10 psi.
Your looking up the wrong Boyle (y)
 
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Zigisla

Zigisla

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Your looking up the wrong Boyle (y)
How many are there. Can you point me in the right direction.
I am well aware of temp and pressure but the "boyles law" I looked up is for volume and pressure where temp is constant.
 

dave newell

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Boyle's law details the mathematical relationship between pressure temperature and volume in a closed vessel. You no doubt read the Wikipedia stuff but that doesn't actually cover it all, Wiki says P1V1=P2V2 but the true formula is P1V1T1=P2V2T2. Pressure volume and temperature are inherently linked in a closed vessel.

In a tyre the volume stays pretty much the same but as it is driven over a road surface it heats up and sooner or later that heat is passed into the gas inside. This rise in temperature while volume stays relatively stable leads to an increase in pressure which is proportional to the temperature increase.

As I said earlier, it is the sole reason a diesel engine actually works!

D.
 
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Zigisla

Zigisla

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Boyle's law details the mathematical relationship between pressure temperature and volume in a closed vessel. You no doubt read the Wikipedia stuff but that doesn't actually cover it all, Wiki says P1V1=P2V2 but the true formula is P1V1T1=P2V2T2. Pressure volume and temperature are inherently linked in a closed vessel.

In a tyre the volume stays pretty much the same but as it is driven over a road surface it heats up and sooner or later that heat is passed into the gas inside. This rise in temperature while volume stays relatively stable leads to an increase in pressure which is proportional to the temperature increase.

As I said earlier, it is the sole reason a diesel engine actually works!

D.
Whilst I will not die in a ditch over this it must be pointed out that the relationship which includes a veritable temp is Charles law. A combined gas law has the equation of P1V1/T1 etc so if you can point out another site not wiki that states your formula great. If not I think it is more likely the combined gas law not boyles's.

Anyway. It does seem that 10psi is the norm(y)

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funflair

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Combined gas law seems to be a bit of everybody's although I thought it was Boyles as well.

http://www.calculatoredge.com/chemical/combined gas law.htm

Anyway 10 psi is about right as you say, and it is amazing how quickly this takes effect, within 10 miles in my experience.

Martin

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Oct 8, 2014
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Boyle's law details the mathematical relationship between pressure temperature and volume in a closed vessel. You no doubt read the Wikipedia stuff but that doesn't actually cover it all, Wiki says P1V1=P2V2 but the true formula is P1V1T1=P2V2T2. Pressure volume and temperature are inherently linked in a closed vessel.D.

Boyle's Law and Charles' Law equations can be combined into a single equation, representing the Combined Gas Law, which states: The volume of a gas sample changes inversely with its pressure and directly with its Kelvin temperature.

This is what Dave quoted above.

See https://www.easycalculation.com/chemistry/combined-gas-law.php

I have filled it in for typical Tyre volume of 1.5 cu ft, a starting pressure of 4 bar, and initial temperature of 20 deg C (293 K). If the temperature rises by 10 deg C - due to flexing of the tyres as the vehicle moves, then the pressure will rise to 4.1365 bar (Excuse mixing of units!!)

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Zigisla

Zigisla

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Many thanks for the confidence boost. (y)Beginning to think there might have been something untoward. Now I will have weigh MH and get correct pressure as I am sure 80 psi is too hard. :rolleyes:
 

DBK

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Many thanks for the confidence boost. (y)Beginning to think there might have been something untoward. Now I will have weigh MH and get correct pressure as I am sure 80 psi is too hard. :rolleyes:
It probably is, my guess, having just Googled your MH, is the fronts should be no more than 60psi. Not sure about the back as you seem quite large there :):) but less than 80 I'm sure.

And for gas expanding when it gets hot think hot air ballons. If it can't expand, the pressure will rise. If it can expand the density reduces and the balloon is away!

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2657

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It probably is, my guess, having just Googled your MH, is the fronts should be no more than 60psi. Not sure about the back as you seem quite large there :):) but less than 80 I'm sure.

And for gas expanding when it gets hot think hot air ballons. If it can't expand, the pressure will rise. If it can expand the density reduces and the balloon is away!

Don't start confusing us with density now, got enough with pressure, volume and temperature!:)
 

PeteH

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AND, Then, There are the "laws of partial pressure". AKA the reason your gas fridge works!.

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