What PSi

[spic]

Im running 205 40 17s, what psi would you keep them at on the track once warm ? and would you keep the rears the same as the front...?

Thanks

Steve.

[Black_Potato]

Depends on the tyre, especially the rigidity of the side walls.

Something that has a fair amount of stiffness will probably want to run at road pressures on track, so R888 hot around 31psi, which would be 23-24 cold.

Tyre presure front and rear when hot would normally be the same but the starting point might be a little different. ie. lots of power maybe the rears a little lower, lots of load on the NSF then that could be a little lower. But at that point its more tuning than a speciic rule set.

Nangkangplingplongs would probably want 40psi to stop them folding over.

Whatever you do be sure to reset them before driving home, espcially if its wet/raining.

[spic]

Im running normal car tyres at the moment (Kuhmo 31's) but im getting quite a bit of understeer on the road on roundabouts but wasnt sure if i had to much presure in them (32psi), want to get it right before I head to track ... for information the car is on Koni adjustables.

Ta

Steve.

[Black_Potato]

Try changing the front damper setting then, I'd suggest going several clicks softer.

[spic]

mm Thought you may say that..

Ta.

[m8782538]

205/55/15 on mine is 32 front and 30rear, works fine. Running avon ZV3 rubber, fine in the dry, have to watch you right foot in the wet.

[Mikey_Boy]

205 / 40 17 on R888s on my track car - I run these at 30 - 32psi all round with no issues. Your turn in problem is probably a combination of too much tyre pressure (as mentioned above) and too little negative camber at the front - this really hurts the turn-in response.

For info - I run 2.75 neggy at the front, 2ish at the rear..

Hope that helps!
Cheers,
Mikey_Boy

[UweM3]

I am staying well out of this. I am completely the opposite.

[Mikey_Boy]

Actually - on Uwe's point above, I made a bit of a boo boo on my tyre pressures I use for track - I run 30 - 32 COLD on my R888s...

It was a tip I picked up from Subaru trackday folks - they found better wear rates doing this on similar size R888's and the tyres didn't go off so quick on track...

Anyone else found this?

Cheers,
Mike

[UweM3]

Actually - on Uwe's point above, I made a bit of a boo boo on my tyre pressures I use for track - I run 30 - 32 COLD on my R888s...

It was a tip I picked up from Subaru trackday folks - they found better wear rates doing this on similar size R888's and the tyres didn't go off so quick on track...

Anyone else found this?

Cheers,
Mike

Well, I wanted to stay out.....

I don't know how many times I posted exactly the same as your friends from the Subaru forum.

Do I need to buy a japanes car with a fan blower under the bonnet till somebody believes me

Also running ROAD tyres with slick tyre pressure is so wrong IMHO. They DO NO perform any better with low pressure, quite the opposite in my opinion.

But why do I bother.

[Mikey_Boy]

Well I believe you Uwe!!

[UweM3]

Well I believe you Uwe!!

a classic example is the Conti sportcontact 2. runs best with 5psi
OVER recommended road pressure.
Lower the pressure on that tyre and you end up with a spongy steering response and overheating tyres.

I run my Dulops DZ02 at 40psi HOT. Sometimes I add 2psi to the rears on a hot day.

Cold pressure is useless. You need to get them up to working temperatur and this is related to ambient temperature AND driving style.

If somebody is using the tyres hard, a lower cold pressure is required. But you have to be careful with low starting pressure, low section tyres have been seen jumping off the rims in sharp bends if used too hard before working pressure is reached.

[Black_Potato]

Uwe.. I said something similar at the start.. i.e depends on tyres and that some, especially those with soft sidewalls may do better with higher pressure.

Re camber, caster, toe, spring rate.. etc.. etc.. they all have effect at varying rates as you progress through a corner, breaking, trail breaking, initial turn in, mid corner, etc it so on..

The probem is do you say go read 10 books and do 2 years theory before you do your 1st trackday ;)

The plus side is on a track day you can have a play and see what suits, just put it back before you drive home !

[UweM3]

Uwe.. I said something similar at the start.. i.e depends on tyres and that some, especially those with soft sidewalls may do better with higher pressure.

Re camber, caster, toe, spring rate.. etc.. etc.. they all have effect at varying rates as you progress through a corner, breaking, trail breaking, initial turn in, mid corner, etc it so on..

The probem is do you say go read 10 books and do 2 years theory before you do your 1st trackday ;)

The plus side is on a track day you can have a play and see what suits, just put it back before you drive home !

I am just a little bit bored of the usual " start at low psi" advise without taking anything of what you posted above into consideration. It's one of these interweb myths, the race teams do it, so it MUST be good.

[Mikey_Boy]

A bit more info for the thread - just back from a Donington trackday - started at 32psi cold on R888's - built up speed fairly slowly working up to giving them a good bollocking - the tyres just got better and better... Wear rate was fine as well.

[UweM3]

A bit more info for the thread - just back from a Donington trackday - started at 32psi cold on R888's - built up speed fairly slowly working up to giving them a good bollocking - the tyres just got better and better... Wear rate was fine as well.

what HOT psi did you end up with? Cold pressure doesn't mean a lot.

[Mikey_Boy]

Indeed - about 42psi when properly toasty...

[UweM3]

Indeed - about 42psi when properly toasty...

that's what I like to run as well. 40-42psi hot.b