tire pressure?

Just checked the tire pressure (car has 18"s) and it's pretty darn low 29ft/35rr vs. 36/44 factory rec. However, the car really seems to be handling well right now. Should it be handling better with this lower pressure, and should I continue to run them this low? TIA

We've had extensive discussions about this on the "old" 993-996 board. The consensus was that for the US, a great compromise was 32 FR and 36 RR. If you're driving at real high speeds, the factory pressures HOT (not cold) are probably very good. Again, this only works for the US where speeds are real low, in Europe where you'll hit 100MPH every day, this is probably a tad low JM

Jean-Marc was the "compromise" temperature 32F/36R a hot or cold temp? thanks Mike in Chi

Also, any significance to the fact that factory recs (36/44 on 18") have an 8 lb variance between f and r vs. 4 lb for the compromise?

Cold, street pressures are given cold, track pressures are given hot JM

Thanks JM I appreciate the info. Mike

What's the typical diff between hot and cold - 4 lb?

It depends on where and how hard you drive. On the track it could be as much as 8-10 pounds.

"It depends on where and how hard you drive" Then how do we apply that to Jean-Marc's: "the factory pressures HOT (not cold) are probably very good." It seems a cold number would be better. What is your rec on cold numbers for 18"s? TIA

I always run 32/35 cold on the streets and as low as 28/31 on the track during very hot days. For those who have a 2WD car, a 2 psi differential is even better. Bear in mind that these are for street tires.

Thanks Viken. So your saying you run 32/35 on 18"s on the street? What about the 2 psi diff? Does that mean 33/35?

I know I'm late in the game in this thread, but isn't the factory recommended PSI for "cold" rather than "hot" tires? I've been driving my c4 inflated at the factory 36/44 cold pressure levels - should I really be driving with significantly lower inflation levels than the factory recommendation? I've always driven all my cars (I've had many) at factory recommended inflation levels - is there a reason why the 996 is different (well - I know it has no peer among cars under $100k - and few above that, but I mean re: inflation levels).

I think most 2WD people have been happy with 32/34. I suggest that you experiment with your pressures by starting at 36/38 and working your way down. I am only suggesting the higher psi's because I don't know how hard you drive your car on the streets. The harder you drive, the hotter they get. Shoot for a hot pressure of 40 to 42 psi's. Also, the actual tire you are running can and will react slightly differently to the same pressures.

The factory recommended "cold" 36/44 is the least understood set of pressures. This contributes to a load of understeer, harsh ride and premature rear tread (center) wear. Some say that these pressures are a must for very high sustained speeds (Autobahn) but this only means that the 44 will soon reach and exceed 50 which is too hot for the tire. So, I really don't know why the factory recommends 36/44 but whoever tries lower pressures, finds better grip, better handling, more even wear and a better ride.

"I think most 2WD people have been happy with 32/34. I suggest that you experiment with your pressures by starting at 36/38 and working your way down. I am only suggesting the higher psi's because I don't know how hard you drive your car on the streets." Thanks for taking the time to help out. I drive it VERY spirited ALWAYS.

One more thing, you drive a 993, right? Does this advice change at all for the 996.

No, I find that most 911 cars with the heavy weight bias to the rear react about the same to tire pressure differences. Also, Porsche's factory recommended pressures have also been the same on all 911 cars for as long as I remember.

Viken, Wouldn't over inflated rear tires grip less, leading to over steer? I know when my track tires over heat, they get really "greasy." My solution is to drop the hot pressure of the axle that is not gripping. Would you expand on that? Definitely 44 psi cold would be way to high on the track.

Yes, of course overinflated tires will have less grip but you don't need ultimate grip when driving Autobahn speeds in a straight line.