M11

Can anyone give me an idea of what pressure to put in my tyres for use on the track.

I don't know if tyre sizes make a diffrence but mine are 215/40x17's.

Many thanx

Pete Croney

Add 5 psi all round.

M11

Thanx very much as I wasn't sure because this is a new experience for me.

daw

(Assuming we are talking about road tyres...)

...THEN... as soon as you come off the track and have lightly driven around for at least 5 minutes at about 10-20km/h, park your car back in its pit garage (without using the hand brake... it should be dead flat in there) and re-check your tyre pressures. You will often find they have sky-rocketed to around 50psi which has corresponded with your car slipping around on the track too much.

Now set them to around 44 front, 42 rear and see how it feels next time out. Depending on your suspension mods etc. you may want to set them at 44 all round but I am assuming a standard car.

Oh one other thing, they may seem noisier when you go back out after lowering the pressures, but that's because they are now working harder.

Have fun!

David

Mac's Power

I have a set of track wheels and had them filled with nitrogen. The pressures dont vary anymore. Recommended. I run around 38 fronts and 36 rears . The still squeal a bit but they do grip.

Paul.

daw

Paul,

I take it these are 'R' spec tyres then? Which ones are you running?

Nitrogen is a good idea. The pressure changes are in fact due to the amount of water in the air in your tyres. Nitrogen leads to much more stable pressures.

David

bugwaan

I've just completed a high performance driving course and they reckon 50psi all round on the track.
As they r also race car drivers i figure they know what they r on about.

daw

Bugwaan,

This would be the sort of pressures you would run in 205/50/16 Potenzas mainly due to their sidewall flex.

The 215/40s don't have the same sidewall flex and running 44 should allow a little more grip.

I can only figure that Mac's Power's recommendation of 38/36 is for an "R" spec tyre as these generally have much better construction than a normal road tyre and don't flex as much.

There's no simple rule for what pressures you should run but the three above are a good starting point.

Regards,

David

Hoppy

David in Oz, can you recommend pressures for slicks? I have been told to run them lower than road tyres, so have run mine around 30/32psi. The grip is fantastic, but...

They get very hot, so much so that the surface becomes like glue, picking up loads of crap - marbles off the track (upsetting the balance), *** ends from the paddock welded in!

Last year I was running 16in slicks and after a couple of track days I noticed severe cracking of the inside side walls.

I ditched them and am now running 210/620x17 Dunlops (identical tyres, just bigger). Now after only one track day on these, one tyre shows tiny cracks on the inside wall. The other three are fine and I don't know which corner the cracked tyre is off, but I suspect left-front.

I'm running 7in wide rims but I know 8in is recommended. I suspect severe side wall flexing is causing the problem. Do you agree? Would bumping up the presures to 40psi or so help?

Thanks,

Richard.

[This message has been edited by Hoppy (edited 08 May 2001).]

bugwaan

David

The 50PSI tyre pressure on the track was for my MY01 Subaru Wrx 215/45/17 fittment.
The car went like a cut cat and tyre wear was even. Way too hard for the road but great for the track, & the extra PSI helps them run cooler.

Mac's Power

Sorry for the delay in replying.

my best suggestion is to play around with the pressures. I found the above to my liking but some like them a little harder. Try the first session and decide then. if the tyres are squealing too much then put a little more pressure in them or dont steer too much!

Paul.

TURBO7379

Hoppy ,
I am running 20/61-16 michelin slicks on standard 7x16" rims . I run them at 27 psi cold pressure on advice from my supplier . I have no problems with cracking and I have fantastic grip . The only problem I have is the outside shoulder of the LH front wheel tends to wear first but that can be solved by rotating the rims from hub to hub . Have the tyres been sitting unused for a long time as this could be a reason for the sidewalls cracking . This can be a problem if part worn slicks are left unused , uninflated and not stored properly . They should be stored in a cool , dark dry climate . Maybe over-inflation is causing the cracking . I'll e-mail you with the contact details of my tyre supplier when I get home and maybe he could help you . He has been supplying motorsport tyres for 25 years and knows his stuff .

Derek

Hoppy

Turbo, thanks mate. Maybe storage is the problem - I've no idea how old they are or how they've been kept. But when my son was kart racing seriously, tyre care was a major priority and they were always stored in the spare bedroom. Three sets of slicks and four sets of wets (from new, through intermediate to almost knackered) - very popular with the Missus and staying guests! Lends a lovely aroma to the room

Any advice greatly appreciated. Thankx.

Richard.

daw

Hey Hoppy, sorry for the delay.. it's quick to get all those 1s and 0s down here but it's a long way back up :-)

Problem here is that different slicks are designed to run at different pressures - there's no standard, but they are generally designed to run a lot lower that road tyres due to their construction.

From what you are saying it does sound like you are running yours slightly too low thus causing them to generate all that excess heat due to them squirming about, this may also be what is affecting the sidewalls (unless you are doing some ripple strip hopping or other off track excursions:-)). Try 34-35 see if that makes a difference, it may not seem like much but slicks are generally very pressure sensitive.

Good luck!

David