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27 Jan 2003
Hi Chaps,

Just a thought, tyre pressures... does anyone know the correct pressures for there cars for 16" 17" and 18" tyres.

What tyres/pressures are you running on the road and track and how different are they from the Porsche recommendations.

I would be very interested to know and I would think it would be a useful matrix to post for future reference.

Migration info. Legacy thread was 19134
I use 38 front, 42 rear. I have 18" hollow spokes and harder Roock suspension.

The Porsche recommended pressures are higher and would give too hard a ride.

Migration info. Legacy thread was 19136
Dont Porsche reccomend 36 F, 44 R for 18's ??

I'm constantly messing around with my pressures as im trying to get rid of my tramlining. I currently run my 18's with 36 F, 42 r.

Oh - car has been lowered with a RUF set up - which might contribute !!

Migration info. Legacy thread was 19138
Standard 993 C2 with 17in Cups: 2.5 bar F and R according to handbook. All feels fine to me...

But if any of you have any recommendations worth experimenting with, let me know!

Migration info. Legacy thread was 19153
for 17" the hand book says 36psi allround (is that the same as 2.5 bar?) and that feels ok on road. On track I lower it enough (@28psi) so that after a few laps it heats up to 36psi. That feels about right to my inexperience hands/bum.

Migration info. Legacy thread was 19156
I had Continental Super Sports fitted to my car.

As you probably know, the tyre pressure settings are given in the engine compartment. On my car these are 2.0 and 3.0 bar.

However, I got in touch with Continental direct and asked a similar question. Thier response was 2.5 bar front and 3.0 bar rear from cold and don't play with them.

I checked the tyres at the weekend and found the pressures were all very low. The ride is very different at the recommended pressures but I wouldn't know enough to adjust the pressures for performance.

I'd get in touch with the tyre manufacturers technical department direct.

Migration info. Legacy thread was 19165
17" on my 993 - & I go for 37 psi all round ('cos I haven't read the handbook for a while - looks like I've subconsciously added 1 psi somewhere along the way)

Has anybody tried filling their tyres with nitrogen rather than air? It costs £7 for all four tyres from your local ATS etc, and apparently keeps the pressures constant even during hard driving / track work etc, and massively lengthens the time your tyres maintain the correct pressure before needing to be topped up.

I have done this yet, as my tyres will need replaced soon - but am thinking about it for the new set.

Migration info. Legacy thread was 19168
Hmmm.... Air is approx 80 % nitrogen anyway, I really don't think it would make any difference to the performance at all using 100% nitrogen.

It would certainly still increase pressure with temperature (law of physics), and would still leak out at the same rate. How can those claims be justified ??

Migration info. Legacy thread was 19176
From F1 web site -

Formula One tyres are normally filled with a special, nitrogen-rich air mixture, designed to minimise variations in tyre pressure with temperature. The mixture also retains the pressure longer than normal air would.

All racing tyres work best at relatively high temperatures, Formula One dry 'grooved' tyres are typically designed to function at between 90 degrees Celsius and 110 degrees Celsius. To ensure that the tyre pressure stays as constant as possible during these changes in temperature a special mixture of low density gases is used to inflate them rather than air.

Migration info. Legacy thread was 19180
Weird I recently fitted 18" GT3 alloys on my Boxster as was wondering the same thing, "what should be tyre pressure be". Looking in the Users Manual it only mentioned 17" wheels then one day I was loading some shopping into the storage space under the bonnet and I saw an official Porsche sticker which gave the tyre pressures for 16"/17" and 18" tyre sizes. It suggested that for the 18" the cold tyre pressures should be 29 up front and 34 at the rear. I will take a picture of it and attach it soon as I can. The pressures are much lower than expected. Subsequently I dropped my fronts from 36PSI to 33 up front (rears were all ready about 35PSI) to feel what the difference is like and the steering is noticeably heavier. Although I must check what 33PSI on warm tyres equates to when the tyres are actually cold. Not sure if anybody cares but there you go.

Migration info. Legacy thread was 20085

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