Tyre pressures

[Bushy]

So who is doing what?

So on the standard RS4 we are told 36psi front 34 psi rear

Is everyone sticking to this or not?

And for those of you already with 19" rims and 30 profile tyres what tyre pressures are you running?

[Thorney]

The same. Will up it 2 psi all round for track.

[DuncS3]

Thorney, upping PSI by 2 all round, is that something sufficient for all cars as a general rule of thumb? The S3 with 18" rims is 36 psi all round standard

Dunc [img]images/graemlins/s3addict.gif[/img]

[Thorney]

There isn't really a hard and fast rule, all depends on car, weather etc. Generally you up them all round and see how you get on.

[Prawn]

For my S4 I run 36F, 38R on the road.
For track days I also increase 2psi all round, if its wet I tend to leave at 38/36 to help them key in a bit more.
In the dry to tend to get more ultimate grip with higher pressures but they will let go less progressivley.

[Stevecab]

forgive me if im wrong (i usually am!) but surely as going around a race track after a couple of laps the tyres will be getting very hot, therefore is it not safe to assume that as the air inside gets hot the tyre will be become more pressurised due to the air expanding??
I did a track day last year and most people were letting a couple of psi OUT to allow for the increase in pressure! [img]images/graemlins/spineyes.gif[/img]

[johneroberts]

Here speaks the knowledge of 30 plus trackdays. 38 psi is the norm for a trackday outing in a RS4 [img]images/graemlins/grin.gif[/img]
Give it large
CBP [img]images/graemlins/biggrin3.gif[/img]

[Greg_S]

this is why you can have your tyres filled with nitrogen instead of normal air because it is more stable in different temps than normal air. [img]images/graemlins/s4anogaro.gif[/img]

[Taipan]

most people were letting a couple of psi OUT to allow for the increase in pressure!

I could be wrong too but isn't that -ie taking pressure out of a warm tyre- something you read at the Air-Pressure stands as an absolute NO-NO ?

Or does that apply only to daily usage ?

Eric

[Andiroo]

You mention an interesting point there Steve [img]images/graemlins/wink.gif[/img]

The reason for increasing tyre pressures on trackdays is for a number of points, all primarily to stop you destroying the tyres you drive home with;

- To stop the tyre from overheating
- To stop any damage to the sidewall
- To make sure the tyre stays on the rim under heavy cornering

John is corect in that 38psi is about right for an RS4, this becoming around 44psi when they are hot [img]images/graemlins/shocked.gif[/img]

Greg you are correct in that Nitrogen is alot more stable under increased temperature, although you need to manually increase the pressure a lot more to protect your tyre and sidewall.

Eric you a also correct. By all means check your tyre pressures when hot, but under no circumstance let any air out until they are cold - you let out 2psi when hot and you are actually letting out 6 or 8psi actual [img]images/graemlins/blush.gif[/img]

Funny thing is this rule only applies to tyres you are going to drive home on. If you take a spare set, which you are prepared to damage just on trackdays, then you will probably find like I have, that running a lower psi increases grip to a large extent [img]images/graemlins/laugh.gif[/img]

Andiroo

[dog]

I am aiming for 42 psi cold. As I have Smartire fitted, it is amazing what the pressure really does. The 42 is really 40-41, as just 2 km drive from home to the petrol station is enough to increase the pressure. 42 is 47-49 while driving hard. Letting air out while it is hot is a flat tyre and buckled rims.