944 tyre pressures

[nick3814]

Hi there, I have just had new turbo style 17" cup alloys fitted (the 5 spoke ones with the slight twist) to my 1988 944 Lux, I have been advised that the tyre pressures for this size (255 rear and 225 front) should be 36lbs does this sound right as it seems a bit high to me.

Thanks

Nick Stevenson R3 RO

 

[idwoodvale]

Have had 17" cup 3 wheels (255 rear / 225 front) on my Lux for about 3 months now and have ben running at the standard 36psi rear, 29psi front. Have probably done about 1500 ish miles both in town and motorway and haven't noticed any problems, handles fine too.

 

[Guest]

Hi group....

I've a 944 S2 '91 Cabriolet - could someone put me out of my misery and tell me what the normal tyre pressure should be? They're standard 7 spoke S2 alloys, 225 front and 225 rear.

Many thanks.

 

[Melv]

From my memory, book pressures are 30 something front and 44 rear. IMHO, far too high and my 944 S2 wore out the centres of the rear tyres first -a sure sign of over inflation.

Tried 36psi all four and wear evened out and the car handled better.

Rgds
Mel

 

[Fen]

ORIGINAL: Hipster

Hi group....

I've a 944 S2 '91 Cabriolet - could someone put me out of my misery and tell me what the normal tyre pressure should be? They're standard 7 spoke S2 alloys, 225 front and 225 rear.

Many thanks.

I run 36psi all round in my cab on standard tyres.

Note that standard front is 205 - I assume it was a typo but otherwise you have the wrong size.

 

[Guest]

Thanks guys for the replies...

Actually Fen, it wasn't a typo....they are 225's front and rear - could that be why I get a sound like a cat being dragged through a mangling machine, when I turn the wheels full lock?

Cheers.

 

[Diver944]

The S2 handbook for 1989 has the pressure at 36 front and rear. In 1990 they revised it to 36 front and 44 at the rear. I've tried mine at 44 and it makes the handling trully nervous [] so I have both at 36 psi. As Melv said this also yields even tyre wear.

For those without manuals, the official pressures should also be on the yellow sticker inside your petrol flap. Gmund cars who advertise in Porsche Post often have official handbooks for sale

 

[Mikie_gb]

cat being dragged through a mangling machine, when I turn the wheels full lock?

I am not sure that it is the tyres contacting, as I am running N1 235/40 Z 18" up front on a completely standard 944 S with out any bother. (the rears on the otherhand, which are N1 265/35 Z 18" on 10" rims are less happy with the unrolled arches). I am running 36 psi front and 42 psi rear, which was suggested by Michelin for this application. (and the rears still look slightly dished from behind)

 

[Guest]

ORIGINAL: Diver944

The S2 handbook for 1989 has the pressure at 36 front and rear. In 1990 they revised it to 36 front and 44 at the rear. I've tried mine at 44 and it makes the handling trully nervous [] so I have both at 36 psi. As Melv said this also yields even tyre wear.

For those without manuals, the official pressures should also be on the yellow sticker inside your petrol flap. Gmund cars who advertise in Porsche Post often have official handbooks for sale

Its weird that is it not. How can Porsche get it so wrong with the pressures? I cant quite let myself run at 36 all round, so i use 36F 38R. But saying tht the cr@ppy gauges could be 3 or 4 psi out anyway!!!

Would be interesting to find out where that 44psi actaully came from.

 

[Fen]

ORIGINAL: Mikie_gb

I am not sure that it is the tyres contacting, as I am running N1 235/40 Z 18" up front on a completely standard 944 S with out any bother. (the rears on the otherhand, which are N1 265/35 Z 18" on 10" rims are less happy with the unrolled arches). I am running 36 psi front and 42 psi rear, which was suggested by Michelin for this application. (and the rears still look slightly dished from behind)

No Way! I have destroyed 2 sets of 265/35 18's by wearing them around the middle. Remember they balloon at speed.

First one at 38psi, second at 36psi. My current set have half-worn evenly with 34psi in them, so I'd knock lots of pressure out of your's.



Hipster,

Is the noise the tyres (unlikely I suspect) or the 944 TADTS problem of a resonance in the pipes (probably)? That being the case it is worse with bigger tyres and we don't know how to cure it, but a fluid change usually helps quieten it a bit.

 

[Diver944]

Hipster,

I once had my rear 9" wheels on the front with 255 tyres and the clearance was fine, so I agree with Fen your noise could be the famous noisy power steering. Most will 'groan' at full lock, especially reversing. Mines done it for 6 years with no ill effect

Mikie,

Wth 18" wheels you may have to dial in a bit more negative camber at the rear so that the wheels 'lean in' slightly at the top. Some cars are ok just with arch lip rolling but some need more help.

Slim,

I've seen lots of discussion about this pressure increase over the years. My current favourite is that they changed it after some high speed blow outs on the German autobahns, so therefore it's completely immaterial for us slower speed countrys []

 

[Mikie_gb]

No Way! I have destroyed 2 sets of 265/35 18's by wearing them around the middle. Remember they balloon at speed.

First one at 38psi, second at 36psi. My current set have half-worn evenly with 34psi in them, so I'd knock lots of pressure out of your's.

Point taken. I haven't done more than 500 miles on them, and very little at high speeds so wear pattens have not been established as yet. When I get the car back I can experiment more.

The Michelin guy advised this pressure for the tyres, but consider the tyres (N1) are for his purposes, for the 911 GT3 application, one would expect a car of 50/50 weight distribution to require different tyre pressures to a car with the engine strapped to the rump. And I suppose, when you stray from the standard set up on a car ie wheel size, you are pretty much on your own.

 

[Mikie_gb]

Wth 18" wheels you may have to dial in a bit more negative camber at the rear so that the wheels 'lean in' slightly at the top. Some cars are ok just with arch lip rolling but some need more help.

What is interesting, is that the passenger rear tyre is closer to the outer body work than the drivers side. No shunt evidence at the rear of the car, so it might be worth a trip to the alignment shop to get the whole thing double checked, and from what you guys are saying, possibley a workshop with more than average experience with messing with 944s.

 

[Diver944]

ORIGINAL: Mikie_gb

What is interesting, is that the passenger rear tyre is closer to the outer body work than the drivers side

Yes, that's normal. You have to remember these cars were designed in the early 80's before sophisticated cad/cam packages came along. As a result the nearside rear arch bulges less than the offside [&:]

Here's a piccy of mine to show that the nearside (on the left in this pic) sticks out 3cm, the offside is 4cm

 

[Andy Duncan]

I would stick to 36 all round (I use this on my 1990 944S2), 44 in the back is too high, even for rear engined 911's in my opinion (GT3 is 39 in the rear).

In my 993 I dropped the pressure to 36 in the rear. There's been much debate on the high recommended tyre pressures in a number of mags (sorry can't remember specifc articles) suggesting Porsche set pressures too high.

andy