Cold PSI v Climate temperature

Wheels, Tyres, Suspension, Chassis, Faults and Fixes
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billvega
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Cold PSI v Climate temperature

Post by billvega » Thu Jan 25, 2018 6:07 pm

I did post this amongst another thread but didn't get picked up on. Would love to know the answer:

From cold my Dunlops should be 37. But, the cold temperatures vary greatly in uk this time of year and in summer. So, say first thing in morning, depending on time of year can be roughly between 0c and 15c. This effects the psi, so, at what temperature should they read 37? As its warmer now, say 9c my tyres are now 38 cold. But when i did them at say 3c, they were all 37. Or does 1 or 2 psi either way not matter? drives me nuts.

On a long motorway run today, my tyres set at 37psi cold set in 3c weather are now 42psi with mild weather and obviously fully warmed up
XE R Sport 180, MY18, Corris Grey, Black Pack/Venoms, Cold Climate, 40/20/40, Parking Pack, 10-Way Seats & 4-Way Lumbar.


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moose
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Re: Cold PSI v Climate temperature

Post by moose » Thu Jan 25, 2018 6:24 pm

Just having had a puncture repaired I am monitoring tyre pressures at the moment.

I have Pirelli P7’s and they are 34 cold and go up to 37 when warned up.

Mine should also be 37 cold but I have always set them to 34 and they all have 6mm left on the complete tread and the ride and handling is fine.

Bob
R Sport 240ps Bluefire with Templar wheels. Parking pack, blind spot monitor, heated windscreen, folding mirrors, splash guards, privacy glass.


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billvega
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Re: Cold PSI v Climate temperature

Post by billvega » Thu Jan 25, 2018 6:32 pm

moose wrote:
Thu Jan 25, 2018 6:24 pm

Mine should also be 37 cold but I have always set them to 34 and they all have 6mm left on the complete tread and the ride and handling is fine.

Bob
Why would you under inflate? And like my original post, what constitutes a 'cold' temperature 0c? 20c? !! It all affects the psi
XE R Sport 180, MY18, Corris Grey, Black Pack/Venoms, Cold Climate, 40/20/40, Parking Pack, 10-Way Seats & 4-Way Lumbar.


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moose
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Re: Cold PSI v Climate temperature

Post by moose » Thu Jan 25, 2018 6:42 pm

When the car was delivered the tyres were set at 37 cold and the air temperature was 7c. The car would tramline badly and react to bumps etc harshly. I played about with pressures to get the best ride for me and it was 34 set when the air temperature was between 5 and 10c. In the summer months the cold pressure goes up to 37 when the air temperature is 20c.

Bob
R Sport 240ps Bluefire with Templar wheels. Parking pack, blind spot monitor, heated windscreen, folding mirrors, splash guards, privacy glass.


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Bluefire
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Re: Cold PSI v Climate temperature

Post by Bluefire » Thu Jan 25, 2018 6:47 pm

Yes indeed - tyre pressures are meant to be set cold.

However, according to owner data for F-Types you should add 1psi for each 10 degree C drop in ambient temperature.

So generally, assuming a 21 degree average UK summer temp. you would look to maybe add 1.5 to 2psi in winter.
2.0 200 Bluefire R-Sport
Templar wheels, Meridian sound, Advanced parking, Climate pack + Heated rear, Aluminium Paddles - of course :)


Indianajons
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Re: Cold PSI v Climate temperature

Post by Indianajons » Thu Jan 25, 2018 6:56 pm

I believe ‘normal’ ambient temperature for a ‘cold’ tyre is considered to be 20C and that pressure increases/decreases by approx 0.1 bar for every 10C change in temperature. So if you check your tyres at 0C you should reduce the pressure by about 3psi
2017 MY tempest grey Portfolio 180D, folding mirrors, 14 way seats, memory pack, cold weather pack, 360 parking, wi-fi hotspot


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billvega
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Re: Cold PSI v Climate temperature

Post by billvega » Thu Jan 25, 2018 8:11 pm

Ok, now we are getting somewhere. So 20c is the standard temp for a cold tyre. Adding a psi per 10c drop in temp so it looks like this.

20c = 37psi (39 - 40 warmed up)
10c = 38psi (40 - 41 warmed up) This is me now
0c = 39psi (41 - 42 warmed up)

Es correcto?
XE R Sport 180, MY18, Corris Grey, Black Pack/Venoms, Cold Climate, 40/20/40, Parking Pack, 10-Way Seats & 4-Way Lumbar.


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PhilB
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Re: Cold PSI v Climate temperature

Post by PhilB » Fri Jan 26, 2018 8:01 am

billvega wrote:
Thu Jan 25, 2018 8:11 pm
Ok, now we are getting somewhere. So 20c is the standard temp for a cold tyre. Adding a psi per 10c drop in temp so it looks like this.

20c = 37psi (39 - 40 warmed up)
10c = 38psi (40 - 41 warmed up) This is me now
0c = 39psi (41 - 42 warmed up)

Es correcto?
I think the issue is that the tyre should work at optimal pressure after it has warmed up through being driven.
That optimal pressure should be the same irrespective of the temp of the day.
So in cold conditions boosting the starting pressure by one or two Psi will allow that to happen.
I don't think you should worry too much about this as 1 Psi difference is negligible.
Current: XE S 380, Storm grey Pics Black venoms/black pack, 18 ways, BSM, 40/20/40, ICTPro 380, parking pack, spare wheel.
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richmond
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Re: Cold PSI v Climate temperature

Post by richmond » Fri Jan 26, 2018 9:24 am

Maybe we should also take into account the ambient atmospheric pressure as well? The average pressure is 1013 millibars, so if you blow up the tyres during very high or low weather systems they'll be wrong when the pressure returns to normal. :D
John
2016 XE Italian Racing Red Prestige 2.0i 200
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moose
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Re: Cold PSI v Climate temperature

Post by moose » Fri Jan 26, 2018 10:18 am

Fill them with nitrogen is the answer ! Pressure in the tyre will only change by a fraction compared to air when the temperature changes.

Bob
R Sport 240ps Bluefire with Templar wheels. Parking pack, blind spot monitor, heated windscreen, folding mirrors, splash guards, privacy glass.


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