tyre pressures

[zinzan1001]

Hi there, need a little help. i have a BMW 520d 2009 but have replaced the original run flat tyres which were on the car to normal ones. Dunlop 245/40/r18 w93 and would like to know the recommended tyre pressure as ive researched this and seem to get different answers. thanks

[gun12b]

https://www.tyresafe.org/check-your-pressures/car-...

[Smuler]

zinzan1001 said:

Hi there, need a little help. i have a BMW 520d 2009 but have replaced the original run flat tyres which were on the car to normal ones. Dunlop 245/40/r18 w93 and would like to know the recommended tyre pressure as ive researched this and seem to get different answers. thanks

Assuming the tyre size is the same, use the same pressures.

[E-bmw]

^^^^ Wot ' e said.

Tyre pressure are size-for-size the same from RF to non RF.

[zinzan1001]

ok thanks always led to believe run flats were different because of reinforced walling

[Pica-Pica]

gun12b said:

https://www.tyresafe.org/check-your-pressures/car-...

I have just used that site to check my 335d F30, and it disagrees with door label. I am trusting the door label. This site then says e-mail us if you think we are wrong! No, get it right.

[zinzan1001]

just done that myself and they are different to what kwik fit say

[gizlaroc]

Generally I add 2psi over runflats and this tends to be correct.

There is a pretty simple way to test if you have your tyre pressures correct.

Set it at cold and then after a nice run check them again.

If the pressure has increased by less than 4psi the pressure is too high, if it has increased by more than 4psi it is too low to start with.

You want an increase of 4psi from cold to hot.

[Pica-Pica]

gizlaroc said:

Generally I add 2psi over runflats and this tends to be correct.

There is a pretty simple way to test if you have your tyre pressures correct.

Set it at cold and then after a nice run check them again.

If the pressure has increased by less than 4psi the pressure is too high, if it has increased by more than 4psi it is too low to start with.

You want an increase of 4psi from cold to hot.

That sounds a very arbitrary and inaccurate way to set a tyre pressure.

[zinzan1001]

i think we have agreed that run flats and non run flats are generally the same pressure give or take the odd psi so i will revert back to what it says on the inside door..thanks guys for your help

[HustleRussell]

gun12b said:

https://www.tyresafe.org/check-your-pressures/car-...

Matches my car / sticker. Useful website.

[gizlaroc]

Pica-Pica said:

That sounds a very arbitrary and inaccurate way to set a tyre pressure.

Why?

Think about it for a second. It is an almost perfect way to calculate tyre pressure.

The difference between cold and hot tyre pressure should ideally be between 2-4psi.
If you are seeing a bigger increase it means your pressures are too low to start with.

[gizlaroc]

A quick google search, this brings up the first tyre manufacturers document on tyre pressures and they mention the 4psi rule.

https://www.coopertires.com.au/media/1400/cooper-d...