GT2 on Track

[PHOENIXUK]

Going to try out some slicks, does anyone know the pressures I should be running when 'hot'. Slicks are a medium compound, thanks.
996GT2

[keep it lit]

2 bar or 30 psi when hot all round works the best for me on slicks 996.1 gt3.

You will enjoy them!

Ade

[cwin]

You really need to run hard compound on the rear and medium on the front for the best results, watch the rears don't go off quick if your are runing mediums,

[keep it lit]

cwin said:

You really need to run hard compound on the rear and medium on the front for the best results, watch the rears don't go off quick if your are runing mediums,

thats exactly the set-up i'm going to run on sunday... so watch out escort man!

[sportsandclassic]

keep it lit said:

thats exactly the set-up i'm going to run on sunday... so watch out escort man!

You will be able to see my new flashing high level brake light.... Best get used to that view!

[keep it lit]

sportsandclassic said:

You will be able to see my new flashing high level brake light.... Best get used to that view!

oh dear...

[sportsandclassic]

keep it lit said:

oh dear...

I know, I just potter round and keep well out of your way ! Dangerous!

[Lambo fan]

Hello Gents

I just bought a 997 GT2 and am trying to find the best pressure and medium on the road before I venture onto the track with it. The handbook suggests 29psi front and 34 rear with standard cup tyres filled with air. I have now filled them with Nitrogen. Any change? This is my first car with onboard pressure sensors ... and it's a bit of a surprise how all the presures change as the tyres warm up.

Thanks

[Andiroo]

Lambo fan said:

Hello Gents

I just bought a 997 GT2 and am trying to find the best pressure and medium on the road before I venture onto the track with it. The handbook suggests 29psi front and 34 rear with standard cup tyres filled with air. I have now filled them with Nitrogen. Any change? This is my first car with onboard pressure sensors ... and it's a bit of a surprise how all the presures change as the tyres warm up.

Thanks

Interesting point mate

1) why Nitrogen filled?
2) Oem cups with Nitrogen - no idea, but should follow the rules of nitrogen and not expand under load?
3) Cups on my 996, albeit less power than a 7GT2, raised around 4-6 degrees C on hot laps, however this was balanced (deflated) with the optimum working pressure of the cups for best results, which if I remember was around 32 fr 36rear - worked a treat

I would therefore assume working with nitrogen on cups, that a starting point of 32/36 wouldn't be far off

HTH

Edited by Andiroo on Thursday 23 February 05:34

[Nurburgsingh]

Nitrogen will still expand when hot... All gases do.
The advantage is that the expansion is linear, the dirty mix you find in air means your expansion rate could be all over the shop.

[wildman0609]

Lambo fan said:

Hello Gents

I just bought a 997 GT2 and am trying to find the best pressure and medium on the road before I venture onto the track with it. The handbook suggests 29psi front and 34 rear with standard cup tyres filled with air. I have now filled them with Nitrogen. Any change? This is my first car with onboard pressure sensors ... and it's a bit of a surprise how all the presures change as the tyres warm up.

Thanks

nitrogen will need to run the same hot pressure as air will, it will just expand at a slightly different rate to air.

you need to work out the hot pressure you need, then let the tyres cool to cold (leave over night usually) and then you have you cold pressures for track use.

[GrahamSaunders]

Lambo fan said:

Hello Gents

I just bought a 997 GT2 and am trying to find the best pressure and medium on the road before I venture onto the track with it. The handbook suggests 29psi front and 34 rear with standard cup tyres filled with air. I have now filled them with Nitrogen. Any change? This is my first car with onboard pressure sensors ... and it's a bit of a surprise how all the presures change as the tyres warm up.

Thanks

Generally on track days you should reduce the tyres pressures as they will heat up more under the higher loads and therefore pressures will increase. its often quite a significant pressure drop. Advice I was given was to aim for the standard road pressures when hot - and so far this seems to have worked well on my GT3. However, you then need to pump them up again for the journey home, so unless you are using a trailer you will need to pump the tyres up again for which you'll need more nitrogen? Surely you are better off sticking to air.

[Lambo fan]

Thanks Guys

Two reasons for Nitrogn:
1 I was told it reduced road noise. Tyre noise in a 997 GT2 is noticeable, not overbearing but definately noticeable. The N2 didn't seem to make much difference!
2 I was told it expands less that air and so does not cause such high pressures when hot. I have only driven it on the road so far and the pressues go up by around 0.1 - 0.2 bar when hot.

I have my first track day in it in 3 weeks so if it goes up too much and then I deflate to corect, I will inflate again with air. What a waste of £5 for the N2 fill!

[Magic919]

Air is almost 80% nitrogen, so don't expect huge differences.

[PHOENIXUK]

keep it lit said:

2 bar or 30 psi when hot all round works the best for me on slicks 996.1 gt3.

You will enjoy them!

Ade

Thanks for that.

[StuB]

Rich, borrow my ir pyrometer and monitor the surface temp.

Check across the profile and drop pressures to keep below 65-70 Celsius. Your tyre supplier should be able to give a good base pressure. Slicks will work at a higher temp range than road compound but may be similar to 888's.

Let me know about the temp gauge.

[sticks090460]

Nitrogen in tyres reduces road noise,,, of course it does. Snake oil anyone?

[John D.]

sticks090460 said:

Nitrogen in tyres reduces road noise,,, of course it does. Snake oil anyone?

I detect a whiff of something unpleasant too.

[GJB]

sticks090460 said:

Nitrogen in tyres reduces road noise,,, of course it does. Snake oil anyone?

He probably read about it in `Gullibles Travels`.

Apparently when you inflate the tyres with Nitrogen you get a free set of ear plugs included in the price....:-)

[Guyr]

If you track a car Nitrogen is even more of a waste of time.

I had it in my GT2 and GTR which both got tracked. Both still increased pressures a lot on a hard track session (though less than air did). Then you need to drop the pressures when hot after the first session, often by up to 10psi on the rears if they've been worked really hard. At the end of the day it requires topping back to road pressure when cold before the drive home and guess what you do that with normal tyre compressor and it's now got normal air back in the tyre.