Anyone tried lower tyre pressures?

Robertb · 2 May 2017

Over in the 991 section, there is a thread about 'comfort' tyre pressures. The 996 (certainly in my 4S manual) only has the one recommended pressure, and this seems very harsh on UK roads. 36f/44r seems comically high.

The 991 'comfort setting' seems to take 10% pressure out of the rears only... this might make a difference to the harshness I feel on the 3rd world roads round us.

What might the likely effect be on the car's handling... will I lose control on the first bend and die horribly?

Alex · 2 May 2017

Expect greater tyre wear and higher load on the sidewalls, especially when cornering.

Should be named drift setting, not comfort setting.

e92 · 2 May 2017

I run my 996 at 90% of the recommended pressure and it handles beautifully. I have got a very aggressive setup so not sure how a standard car would handle. (Flame suit on :grin: )

Martin996RSR · 2 May 2017

It will be fine. Although you may be able to detect it feeling a little less positive at the rear, you'll actually have slightly more grip as the tyre will be more compliant. The reverse of correlation of this is that if you over-inflate your tyres you'll get less grip out of them as they will become less compliant and will start to bulge, reducing your contact patch. Assuming you're running 18" wheels, your sidewalls will be so small that there probably is little to be gained in softening the tyre by under-inflating it anyway. If you have 17" wheels the effect will be much more pronounced.

If I want to prepare any car for drifting, the very first thing I do is set the front tyre pressure to stock-10% or so, and the rear to stock+15% or more. This includes my 996 for when I really want to get it sideways. Softening the rear by under-inflating it will increase the car's bias toward understeer.

EGTE · 2 May 2017

I knock 10% of the figures myself (because it's rarely fully-loaded, which I expect those figures cater) for.

So that makes 32 front, 40 rear. Comfort is much improved and if anyone can find fault with the handling, they'd be driving waaaaaaaaaaaaay too fast for the public roads.

Alex · 2 May 2017

Manufacturers set these levels as it's an average to cater for all conditions (temp, weather, speed, load, etc.). In a perfect world it won't really matter, just like anything else that's set to a specific level. But when A, B & C are all at their extremes, that's when unwanted things happen.

Regardless of that, the last thing I'd want is to end up having to fight an Insurance claim as the assessor notified the Insurance company that my car was running on under-inflated tyres that could have added to the cause of the accident. Simply not worth it just to add some comfort to your rear end. If you want soft, buy a Jag.

Disco · 2 May 2017

It also depends on the tyre. On my GT3 the recommended cold pressures are 29psi front to 31psi rear for Michelin Cups but higher for winters. The recommended pressures for a 997 Carrera are 33/39 (normal) to 36/44 (fully loaded). Yes the GT3 is a bit lighter, but I don't see any reason that you couldn't put rubber with stiff sidewalls like Cup2s on a Carrera and run them at something like 31/34. I wouldn't ever do that with something like a PS2 though...

For what it is worth: when I used to run a 996 on PS2s I found that 32f/38r worked well.

steve r · 2 May 2017

Center Gravity set mine to 34f 40r rather than 36f 44r

skinny_monkey · 3 May 2017

I wouldn't call 40 psi under inflated!

Robertb · 4 May 2017

Right then, I've dropped the pressures to 34/40. Lets see what happens when I drive it next.

Out of interest, I've done the same to my X5 Sport to try to soften the ride, defo made a difference with no apparent reduction in grip.

911munKy · 4 May 2017

I lowered my tyre pressures a couple of years ago by a few psi each (can't remember the exact amounts but others on a different USA forum had recommended it), the ride was more compliant but it increased the understeer, I'm went back to 36/44.
Rear tyre wear was pretty even (standard geo with slightly more rear camber), wear was slightly more in the centre but I put that down to driving solo most of the time.
Please post your feedback.

RJW1881 · 4 May 2017

Just thought I would pitch in, following advise from my Indy I have been running 28f/ 32r for the last year as it transforms the way the car feels and handles.

I've done 12k miles (sometimes at serous speed) and had no adverse tyre wear but did have to disable TPMS as the pressures are below there perimeters so had a light on the dash all the time.

Give it a try, I think you will like it!

wasz · 5 May 2017

I run mine at least 10% down for Lancashire roads...

e92 · 5 May 2017

I run mine at 32f 36r (I think) and handles very well. The lower pressure is not for comfort but more for handling.

rob_p · 6 May 2017

RJW1881 said:
Just thought I would pitch in, following advise from my Indy I have been running 28f/ 32r for the last year as it transforms the way the car feels and handles.

I've done 12k miles (sometimes at serous speed) and had no adverse tyre wear but did have to disable TPMS as the pressures are below there perimeters so had a light on the dash all the time.

Give it a try, I think you will like it!

That is low! Fascinating the range on here. I have always been in the slightly soft to improve comfort camp.

Anyone tried lower tyre pressures?

Robertb

Yas Marina

Alex

Nordschleife

e92

Monza

Martin996RSR

Montreal

EGTE

Sao Paulo

Alex

Nordschleife

Disco

Portimao

steve r

Spa-Francorchamps

skinny_monkey

Montreal

Robertb

Yas Marina

911munKy

Imola

RJW1881

Spa-Francorchamps

wasz

Paul Ricard

e92

Monza

rob_p

Suzuka

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