ryangambrill

I just want to confirm that regardless of brand and model of tire, the cold pressure should be at the PSI listed on the inside of the fuel door.

In my case, 18" 36 PSI front, 44 PSI rear.

Correct?

Just checked, currently 35 PSI in rear and 31 PSI in fronts.

C4CRNA

Mine is listed under the trunk lid.

SH || NC

ryangambrill

So how do I know the proper cold tire pressure?

I am running the Aumi's HTR Z3's.

sjfehr

Yes, that's correct, the cold pressure should match what's on the sticker (in my case, it's on the fuel door.). When the tires are hot, it will go up a couple psi and it's almost impossible to do anything consistantly then, so they spec them cold instead.

What creates difficulty is that air gauges, especially cheap ones, are notoriously inaccurate. I checked my tire pressures once with 5 gauges I had sitting around (the kids bike pumps, my 12V compressor, a couple pencil gauges, etc) and they had a 15psi deviation! If you can, check your gauge against someone else's. If they read close, they could both be way off, but chances are they're both relatively accurate.

RallyJon

This is a strange question. If you want the tire pressures to match what the sticker says, then you should set them to... what the sticker says.

If you want the car to handle its best, under the conditions in which you drive it, a bit more work it required.

sjfehr

This is a good point I thought probably would get confusing to elaborate on when the question is how to know if your tires match the cold pressures on the sticker. Not to mention a lot of trial and error is required for the best grip with any tire brand/model, car (which corner weights can very considerably with options) and driver, and you'll only notice the difference while driving at the edge of traction, which you shouldn't ever be doing intentionally on the street. As it is, Porsche's recommended tire sizes and pressures create nice, safe, boring, understeer. Which is probably the right way to leave it while off the track, especially for a rear-engine car like this.

ryangambrill

I was just confirming that I was doing everything properly. I then became confused when the mess said that the PSI only applied to "Porsche Approved" tires.

Looks like I could be a bit low on the tire pressure. I have a digital gauge and will test again tonight. Then I will make sure that the tires are inflated to 36 PSI and 44 PSI.

thanks.

Michael Gibney

My 2002 Targa was wearing out rear tires in the middle so that they were down to the wear bars at 6-8000 kilometers. Not happy -- it was expensive.

So, I went down to 38 on the rears and now the tires wear evenly over the width of the tread -- am now at 16000 kilometers and not half worn -- same brand and type of tire.

Porsche dealer checked the alignement -- on all 4 wheels and said -- perfect -- not even a fraction of -- all 4 to within 1% of middle of spec.

Where did Porsche get 44 for the rear?

Go figure!!!

Torontoworker

My INDY (Porsche factory trained and also a former Grand Am Winning crew chief) says the 36/44 for 18" rims is too high and lowered mine last time I was in for service. He also noted that a high PSI on *some* after market alloy's could end up breaking the rims if they hit stuff like potholes and manhole cover lips. He said he had a guy break an HRE a few weeks back and he felt that the 'spec' PSI could have been a factor along with the newer - tougher (but lighter) sidewalls coming on the market pass more impact energy through to the rims now.

sparks259

just to cloud the issue; on my 2000 996 / sumi tires, i use 1#per 100# of car weight and add 2-4 for the motor. even tire wear so far with at least 3 trac days on them.

tgt40

Lowered them to what?

Torontoworker

34/42

My 'plate' says 36/44 and when I asked him about that he says my car was made in 1999 with 1999 era tires. The Conti's I am running are not the orig tires that came with the car (I think they were Pirelli) and tire designs have changed in 10 years. I've been running at the lower settings now for a few months and quite frankly I like the ride far better. He actually suggested I could go as low as 32/40 but not lower then that and not for lapping days, just daily driving. This summer has been very cool and wet around here and the lower settings seems to work quite well as far as grip and confidence.

jasper

That makes 30/34 ? Sounds low for the street no?

Good thread. I *just* set mine to factory after driving around for the last few months at 35/42-ish. Don't know if I'll leave it at factory. I'm thinking to air 'em back down to even the tyre wear out.

SH || NC

And, I tend to increase my pressures during the winter since there is a difference between my garage temp and the temp outside. See T/R's tech info:

Air Pressure, Temperature Fluctuations
http://www.tirerack.com/tires/tirete....jsp?techid=73

Higher Tire Pressures for Winter Driving
http://www.tirerack.com/winter/tech/...sp?techid=168&

And lastly, Altitude
http://www.tirerack.com/tires/tirete...jsp?techid=167