Tyre pressures at lower temperatures.

[Manks]

Hi All

If I want my tyre pressures to be 2.7 bar rear and 2.2 bar front at 20 degrees centigrade, what pressure will they be at 10 degrees?

[ras62]

About 2 psi lower per 10deg C.

[gsewell]

but as tyre pressures are set cold, shouldn't they still be set to the same values as it is likely that the running temperature will also be 10'C lower. Otherwise, we would not be bothering with winter tyres.....

[Manks]

gsewell said:

but as tyre pressures are set cold, shouldn't they still be set to the same values as it is likely that the running temperature will also be 10'C lower. Otherwise, we would not be bothering with winter tyres.....

The Porsche recommended pressures are at 20, I was merely trying to be accurate about pressures when setting them at 10-12.

Not sure whether to buy a set of winter wheels / tyres. Probably won't because its not my daily driver.

[oldtimer]

Agree with ras62......if at 10 deg C you set fronts at 2.1 and rears at 2.6 bar this will equate to 2.2 and 2.7 bar respectively at 20 deg C.....dont think you need to be that concerned about 0.1 bar more or less though.....

[mrdemon]

Set them the same as you would at 20.

[Jaged]

Manks said:

Not sure whether to buy a set of winter wheels / tyres. Probably won't because its not my daily driver.

Just got a set of used alloys off ebay and new wither Avon tyres off Mytyres.
Bought the Boxster S to be my winter hack a few months back, so thought it prudent to shod it with winters.

I'll report how it copes on winters (not N rated).

[Trev450]

Jaged said:

Just got a set of used alloys off ebay and new wither Avon tyres off Mytyres.
Bought the Boxster S to be my winter hack a few months back, so thought it prudent to shod it with winters.

I'll report how it copes on winters (not N rated).

It will transform the car in cold conditions. I've been using non N-rated winters for the last 2 years now and wouldn't have believed the difference they made prior to trying them.

[Rockster]

Manks said:

Hi All

If I want my tyre pressures to be 2.7 bar rear and 2.2 bar front at 20 degrees centigrade, what pressure will they be at 10 degrees?

I don't bother with that. I just ensure the tires are inflated to the recommended pressure when cold no matter what the temperature is.

Where one can run into trouble is if it has been hot and then turns off cold. Then tires that had plenty of air when the weather was hot are underinflated when the temps drop.

And the other side is when the weather experiences a sudden jump in temperature. Then tires that had the right amount of air when the weather was cold can be overinflated when the temps climb.

Sincerely,

Rockster.

[Manks]

Thanks All, I decided to run with recommended pressure at whatever the temperature is.

An aside: Tyre pressures seem to make a lot of difference to the handling of a 991.