Try 36 to 38.
I got 60,000 out of my last road 225/40/18 on 8" rims. (street use only on MY02 STi)

45 to 55 ft/lbs is what is recommended for a 10mm stud.
70 to 80 ft/lbs is what is recommended for a 12mm stud.
85 to 90 ft/lbs is what is recommended for a 14mm stud.

We have 12mm studs on our Impreza's.

These are the safety guidelines sent to us by "The Tyre and Rim Association Of Australia".

No worries...put what they say and what you think is ok then.

I know from 8 years of motorsport in 3 WRX/STi's and from the experience of the top rally teams in Australia that 65 ft/lb is the go and works fine without damaging rim or stud.

But if the Tyre and Rim Assoc knows more then go for it. I (and SRTA, MMS etc) just don't like the idea of stretched studs.

Just reading through, I don't wish to challenge exact pressures that people run.. as this does come down to wheel/ tyre sizes and personal choice.

However, some of you guys are recommending to drop the pressures in the front and increase in the rear. This is incorrect. If you want to reduce understeer (and owning a Subaru, you probably do!) then you need to raise the front pressures a little higher than the rears.. start off with around 2psi at first.

The reason you are doing this is to prevent the front tyre's tread pattern from distorting and increase the rear tyre tread pattern distortion. By increasing the "slip angle" on the rear tyres, you will increase oversteer. Similarly, stronger rear sway bars also help 'load up' the rear tyres to increase this angle as well, amongst other things.
Understanding "Slip angle theory" can really help you determine whether a car will over or understeer.

Hope this helps.

interesting point. my pressues were gained from starting at equal and working the rear up, and finding it worked, never thought about going the other way.

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MY93 Impreza GX 1.8L, 0hp, 0nm

Thats what the guys who did my nitrogen tyres told me too.

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Mazda CX-7
Mitsubishi Evo X MR

Someone payed mention to a Whiteline article earlier... I remember seeing this, and although the rear pressures quoted here seem WAY too low, the same principle applies.

On my street tyres (215/45R17) I find around 36F and 35-34R works well.
On Race rubber (225/50R16) I find *around* 30F and 29R does the trick.. but to be honest, I'm still experimenting with a few ideas lately!

You can get away with much lower pressures on R-comps because they will generally heat up a lot more anyway, the sidewalls are much, much stronger than street tyres and there is far less tread/ grooves... which generally is to aid more with traction and the amount of tyre surface area on the ground etc, but also, having less tread to 'distort' greatly reduces the amount of "slip angle" in comparison to street tyres.

I have a tech article on my forum I will endeavour to post up here... or you could just log onto www.ppmotorsport.com/forum/ if anyone has any further interest?! *shameless plug*

on the topic of reducing understeer by varying tyre pressure, what effect would that have if u already have whiteline swaybars installed?

Every adjustment and modification should work together to eventually give you a more accurate/ better result to what you're seeking to improve etc.

If you have front and rear bar upgrades, playing with pressure increments between front and rear tyres will still give results. However, you might find you don't need to be as 'dramatic' between the incremental differences - depending on how severe your bar thicknesses are etc. My advice would be set the front tyre pressures to something you're happy with, and then drop the rear by 1psi at a time perhaps?

Remember also you want the rear to start reacting in a nuetral to slightly oversteer type of way BUT it needs to be in a controlled and fairly predictable manor. A lot of people fall under the misconception that if the back starts skidding out into large amounts of oversteer that this is 'better' handling. You will ALWAYS sacrifice traction and course times when your car behaves too erratically and the wheels are starting to squeal and make noise. This is why the general rule "smooth is fast" is what we all try to aim for.

(For those of you that don't do motorsport, but enjoy the computer games.. you'll actually find the same is true here as well. The more your tyres piss and moan... the more speed you are losing!)

Im also worried that too high a rear pressure may induce snap oversteer when you come off throttle, or the snap back of doom i see some subi's do in vids when they stack it.