GT3 Tyre pressures

[diesel]

HiGuys, can someone please tell me normal tyre pressures for 265/35 zr 18 225/40 zr 18 sizes, thanks
Regards Andy

[slippydiff]

265 or 285 ? 265 is a winter tyre width.
If you do mean 285 rears they should be 2.7 bar or (37psi in old money)
225 fronts " " " 2.2 bar or (32psi " " " )

[DanH]

Standard tyre pressures are noted under the fuel cap as well. At least they are on mine.

[diesel]

The GT3 wheels are on my 993! as of tonight.

[jeremyc]

slippydiff said:

265 or 285 ? 265 is a winter tyre width. If you do mean 285 rears they should be 2.7 bar or (37psi in old money) 225 fronts " " " 2.2 bar or (32psi " " " )

In my book, 2.7bar = 39psi in old money.

[diesel]

265 s are on at the moment, will 285 s fit?

[DanH]

diesel said:

265 s are on at the moment, will 285 s fit?

285 are the correct size!

[johnfm]

If the tyres/wheels are on a 993, why use GT3 pressures? Maybe use them as an initial guide, but you'll need to adjust to tweak front/rear grip balance.

[slippydiff]

jeremyc said:

slippydiff said: 265 or 285 ? 265 is a winter tyre width. If you do mean 285 rears they should be 2.7 bar or (37psi in old money) 225 fronts " " " 2.2 bar or (32psi " " " ) In my book, 2.7bar = 39psi in old money.

JC, you are of course totally correct. Which begs the question, why does my Drivers Manual state on Page 118 Rear 2.7 bar (37psi)?

What do you inflate yours to ? Anybody ?

>> Edited by slippydiff on Thursday 18th May 21:41

[nervous]

im running 36 all round, as recommended by parr.

[jeremyc]

slippydiff said:

jeremyc said: slippydiff said: 265 or 285 ? 265 is a winter tyre width. If you do mean 285 rears they should be 2.7 bar or (37psi in old money) 225 fronts " " " 2.2 bar or (32psi " " " ) In my book, 2.7bar = 39psi in old money. JC, you are of course totally correct. Which begs the question, why does my Drivers Manual state on Page 118 Rear 2.7 bar (37psi)? What do you inflate yours to ? Anybody ?

Ahh, but if you check page 3 of your manual you'll find they gave the correct conversion.

I use 32/39 on the basis that those ever efficient Germans are likely to have the correct pressure in bar.

[slippydiff]

Ahhh, if they're so efficient how come they let that massive error throughh the net ? freakin Germans. ( Trudges off to get tyre pressure gauge and pump )

Got to say I agree with you about using the prescribed tyre pressures though.
I over inflated the fronts by 2-3psi and it made the car more nervous than, well............... Nervous

[DanH]

johnfm said:

If the tyres/wheels are on a 993, why use GT3 pressures? Maybe use them as an initial guide, but you'll need to adjust to tweak front/rear grip balance.

Oops I didn't spot the bit about this being on a 993!

Dunno if your car will fit 285s. Might need the arches rolled if that isn't a normal size on a 993. Are all the offsets correct etc?

[Merritt]

nervous said:

im running 36 all round, as recommended by parr.

Really? That surprises me.. especially as you have Garys old car which was set up for track use. Does it still have the JZM suspension on it?

Steve

[andy tims]

Whilst 285 is the correct size for a GT3 rear & 225 for the front (MK1). Quite a few people (me included) are running 235 & 265 because thats what the choosen tyre comes in.
With circa 2deg neg camber I'm running 34/43 PSI vs 32/39 as per the book, to help counter excessive wear on the inside edges with almost no increase in nervousness (mine or the car's) or further deterioration in "ride quality"

[GreigM]

andy tims said:

Whilst 285 is the correct size for a GT3 rear & 225 for the front (MK1). Quite a few people (me included) are running 235 & 265 because thats what the choosen tyre comes in. With circa 2deg neg camber I'm running 34/43 PSI vs 32/39 as per the book, to help counter excessive wear on the inside edges with almost no increase in nervousness (mine or the car's) or further deterioration in "ride quality"

I'm the same - 2deg neg on the rear, so ~44psi for the road to try balance out the wear.