Tyre pressures

M

mcbutler

Veteran
 Plymouth
Looks like a dry day or two coming up. I am planning a run to Exeter tomorrow to see about getting some 'dipping' done.

I reminded myself that my car has been stood for a while as temps have dropped so tyre pressures will be low - nudge nudge for anyone else getting the car out after a few weeks away.

Drive safe
 
mcbutler said:
I reminded myself that my car has been stood for a while as temps have dropped so tyre pressures will be low - nudge nudge for anyone else getting the car out after a few weeks away.

Drive safe
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Unless you have leaking schrader valves, why would this be a problem? :?
 
Pondrew said:
mcbutler said:
I reminded myself that my car has been stood for a while as temps have dropped so tyre pressures will be low - nudge nudge for anyone else getting the car out after a few weeks away.

Drive safe
Click to expand...

Unless you have leaking schrader valves, why would this be a problem? :?
Click to expand...

Continental Tyres say:-

Air pressure drops by 1-2 PSI or 0.07 to 0.14 bar with every 10°C
 
Pondrew said:
mcbutler said:
I reminded myself that my car has been stood for a while as temps have dropped so tyre pressures will be low - nudge nudge for anyone else getting the car out after a few weeks away.

Drive safe
Click to expand...

Unless you have leaking schrader valves, why would this be a problem? :?
Click to expand...

I've found the pressure varies quite a bit between summer and winter due to the ambient temp and upto 5psi. Haven't found it necessary to calculate the difference between zero degrees and 30 degrees though. :tumbleweed:
 
Thing is:
Yes your cold pressures will drop with ambient temperatures, mainly due to moisture in the air in your tyres condensing plus most of the elements in air are affected by the pressure/temp relationship.
However, once the wheels/tyres are warmed up the moisture will evaporate and increase the pressure back up to very near summer normal.

There is a strong case for increasing tyre pressure on a cold day could end up with them being over-inflated once warm.

Remember the days when it was a trend to blow your tyres up with Nitrogen? That is because it is dry N2; no moisture. Cold or hot changes the pressures by very little, only the increase of N2 by the pressure/temp relationship.

Physics is a wonderful subject :D :thumbsup:
 
Kiwi_Mike said:
mcbutler said:
getting some 'dipping' done.
Click to expand...

Can you please elaborate? What does this mean? Cheers
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Hi Mike,
My car has the cheesy dark wood interior so I am going to see a hydro dipping company company so I can change the wood finish to carbon fibre or something else thats more up to date.
 
Pondrew said:
Thing is:
Yes your cold pressures will drop with ambient temperatures, mainly due to moisture in the air in your tyres condensing plus most of the elements in air are affected by the pressure/temp relationship.
However, once the wheels/tyres are warmed up the moisture will evaporate and increase the pressure back up to very near summer normal.

There is a strong case for increasing tyre pressure on a cold day could end up with them being over-inflated once warm.

Remember the days when it was a trend to blow your tyres up with Nitrogen? That is because it is dry N2; no moisture. Cold or hot changes the pressures by very little, only the increase of N2 by the pressure/temp relationship.

Physics is a wonderful subject :D :thumbsup:
Click to expand...
Back in the day when petrol stations also had mechanics the air generally came from a compressor inside the garage workshop that would have a drier. Nowadays its those chattering tin boxes, dont know if they have an air dryer in.
Not too sure about the moisture evaporating idea, do tyres get that hot in winter???
 
mcbutler said:
Not too sure about the moisture evaporating idea, do tyres get that hot in winter???
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They can, theoretically. It all depends on the tyres and how hard you push them.

You don't adjust your tyre pressures according to how you are going to drive on a given day, though, do you?

The moisture evaporating and condensing is THE main reason why tyre pressures fluctuate so much with air in them. There is a lot of water in air. :thumbsup:
 
Driving hard in winter may increase the temp a degree or so but not enough to need to change tyre pressure on a road car.

The OP's pont was if you get your car out of storage then consider your tyre pressure assuming you will be driving hard. Valid point and something I keep my eye on as I want to ensure best grip is there when I need it :thumbsup: normally it doesn't matter a toss
 
Hi Mike,
My car has the cheesy dark wood interior so I am going to see a hydro dipping company company so I can change the wood finish to carbon fibre or something else thats more up to date.
[/quote]

Interesting, so they will dip the wood and make it look like Carbon Fibre or Alu? Sounds like a good way to change your interior. Let us know how it goes.
 
Taking a car out of storage is normally, check tyre pressures, fluids etc. then driving gently for an hour or so.

However, how many all year users check tyre pressures when the temp drops - I well remember scraping the ice off the windscreens on those early mornings going to work and coming home at 8° or doing a 250 mile trip - I can’t remember it ever bothered me unduly.

Yes pressure do change by 2/3 psi from hot to cold but does it really matter on a normal drive ?
 
Do I understand that you gents are using compress air to fill the tyres ?
Over at my end we prefer to use nitrogen instead.
 
Well, I dragged my 35 out of storage this morning and straight to the air pump a mile away, My tyres were down 8psi front and 11 psi rear, thats a 25% drop on the rear!!!!!
I check mine weekly when in use and they never lose air so I dont have defective valves, rim seals, cracked rims or porous tyres.
In addition the pressure drops were equal across both axles!
Tyres are Michelin PS4S
Food for thought I think.........
 
sumotan said:
For sure its will loose air. If I park the car for a week all tires will loose about 0.8 - 1 psi .
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Disagree, when mine is in use during summern its checked weekly, losses are pretty much nil over months!
If you are losing air at 1psi a week continually then I would think you hae a leak somewhere, although at 1psi a week its not a worry of course :-)
 
Pondrew said:
mcbutler said:
Not too sure about the moisture evaporating idea, do tyres get that hot in winter???
Click to expand...
They can, theoretically. It all depends on the tyres and how hard you push them.

You don't adjust your tyre pressures according to how you are going to drive on a given day, though, do you?

The moisture evaporating and condensing is THE main reason why tyre pressures fluctuate so much with air in them. There is a lot of water in air. :thumbsup:
Click to expand...
Tyre temps certainly depend on the individual tyre as well, I noticed ny fronts were already warm after just a short distance Michelin PS4S the tyres on my 3500kg transit are stone cold after the same journey as are the tyres on my daughters car.
I guess better grip = more friction = more heat.
A thought on the inflating when cold guidance - although the tyre carcass warms up over a mile or so, would the entire air volume warm at the same rate?
As a large proportion of the air is in contact with a cold aluminium wheel rim that conducts heat away very well, probably not.
 
I suppose the best way to test the theory is to check pressures when cold, then after a few miles, then after many miles.
There are so many variables in a road car you would probably get quite different results every trip.
It would be interesting to compile a spreadsheet to see how much pressures can fluctuate, if a little sad. :thumbsup:
 
Kiwi_Mike said:
Hi Mike,
My car has the cheesy dark wood interior so I am going to see a hydro dipping company company so I can change the wood finish to carbon fibre or something else thats more up to date.
Click to expand...

Interesting, so they will dip the wood and make it look like Carbon Fibre or Alu? Sounds like a good way to change your interior. Let us know how it goes.
[/quote]
I went down to see the guy and showed him the bits in the car I wanted doing.
Both door inserts and window switch surrounds, radio surround piece and the three pieces across the centre of the dash where the vents are and heating controls.
Apparently ten days work including drying and £480 inc VAT!!!Considering the finish is essentially just car paint I am not too sure I want to put that much money into something that will scratch easily.
Might look at wrapping as an alternative
 
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