Tyre Pressure Question

[maddog1982]

So I swapped to MPS4s last July and set the cold temp at 32. Ive noticed today all the tyes seem to be around 28 when stone cold and creep up to 31/32 when warm. The car has had the battery disconnected recently but I wondered if it was more likely the drop in temperture. I assume I need to add about 4psi and they should be around 36 when warm?

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[PeterE]

So I swapped to MPS4s last July and set the cold temp at 32. Ive noticed today all the tyes seem to be around 28 when stone cold and creep up to 31/32 when warm. The car has had the battery disconnected recently but I wondered if it was more likely the drop in temperture. I assume I need to add about 4psi and they should be around 36 when warm?

Tyre pressure vary considerably with temperature, something like 0.2 psi for every degree Celsius, see this Wiki: https://en.wikipedia.org/wiki/Cold_inflation_pressure
I have to adjust mine several times a year and yes, with a cold pressure of 32psi mine (Pirellis) increase to around 36psi in the summer, a bit less in the winter.

 

[hinch]

i only run at 28psi anyway 32 is way too high

 

[W111BOB]

Maybe that is why mine feels 'wandering ' since the michelins went on...

32/33 cold rising to 36 when warm

Guess I should let some air out?

 

[hinch]

put them to 28 cold and it'll make a huge difference

 

[Gregs24]

All tyres lose pressure slowly over time and as Peter says cold temperatures make it worse. As long as all the tyres are losing pressure at the same rate it is just this.

 

[Lowrider Lincoln]

You could have the tyres filled with nitrogen as opposed to air. There are some benefits, temperature does not increase the tyre pressure as much. It makes for a more predictable handling, a lot of circuit track racers have used nitrogen for a while. Not sure of the costs, I just use regular air myself. Mine are inflated to 34/35psi in summer. They are currently at 30/31psi due to cold temps, so goes to show how much pressure fluctuates with temp.

 

[W111BOB]

you still on the Pirellis Chris?

 

[Lowrider Lincoln]

I am Bob. Still got 4/5 mm despite numerous burnouts and drag racing last summer they still look healthy. I've got a brand new set of Pirelli p-zeros to replace these when needed. I know what everyone's said about them. They do have their limitations. Sure, there are better tyres available. But driven accordingly they are suitable for the way I drive.

 

[W111BOB]

wasnt knocking them Chris!


... unfortunately my Pirelli rears both had nails in them (which is fine ... until the nails move or come out!) and they were pretty worn down too
both rears were scrapped - but the fronts are ok (kept them)

seems my Michelins are a tad over inflated as the car feels worse now with them on than it did with the Pirellis!

 

[Lowrider Lincoln]

wasnt knocking them Chris!


... unfortunately my Pirelli rears both had nails in them (which is fine ... until the nails move or come out!) and they were pretty worn down too
both rears were scrapped - but the fronts are ok (kept them)

seems my Michelins are a tad over inflated as the car feels worse now with them on than it did with the Pirellis!

Strange that mate. Not heard anything negative about the Michelin's before. Makes you wonder if all we're led to believe about the MP4S is somewhat over exacerbated. Lowering tyre pressure will result in a softer ride but more flex in the side wall will give vague handling. Increased psi will stiffen up the handling but give less traction, more noticeable in the wet. Finding a happy medium isn't always easy.

 

[Gregs24]

You could have the tyres filled with nitrogen as opposed to air. There are some benefits, temperature does not increase the tyre pressure as much. It makes for a more predictable handling, a lot of circuit track racers have used nitrogen for a while. Not sure of the costs, I just use regular air myself. Mine are inflated to 34/35psi in summer. They are currently at 30/31psi due to cold temps, so goes to show how much pressure fluctuates with temp.

Don't forget air is 80% Nitrogen anyway. For road cars there is little point using pure Nitrogen as it just isn't that critical. Air is free as well !

 

[maddog1982]

i only run at 28psi anyway 32 is way too high

Ah I've just added some air and now stone cold they are 34. Ffs! So we thinking 28 stone cold even though the door says 32?

 

[hinch]

well its personal preference with our fairly large sidewall tyres and lots of power you need to maximise contact patch and allow some slip in the side wall in acceleration to minimise chance of spin. for me that is 28 psi cold you may prefer them rock solid and slippy i don't.

 

[Gregs24]

If you run at 28 long term you will get accelerated shoulder wear.

Ford say 32 so I run at 32. On a track you would run higher still.

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