solomonschris

One: My Harley has nitrogen in the tires. It takes months to leakdown a few pounds, don't know why, and has a much lower coefficient of expansion so pressures are more stable. Does anybody here use nitrogen.

Two: At what ambient temperature do the summer only Pirellis that came on my car become foolish to drive on...not at the track, just normal driving?

Three: What's the best tire? Mine being an S has 20" wheels. I won't drive in the snow, or even before a good rain washes the salt off the roads. I will drive in the cold, if that ever happens again here in Maryland. Thanks as always.....Chris

chuckbdc

I have 20 inch P Zeros too, haven't tried nitrogen. Today (~70 degrees) I tried 33-39 for commute home from work. The tires got up to 36-42 after mild entertainment on parkway along the Potomac- and the car felt great. One day this summer (~85 degrees) I started at 32-37 (where I used to run Mich SuperSports on my Boxter S) and a not too excessive fun run in the country ran pressures up to 38-48, - the rear felt loose. So far (~7500 miles) the P Zeros seem pretty good. But when they go it will be SuperSports for sure. They were way better than the PS2s that Porsche used to use on performance models.

I don't plan to track the car or I'd have to go for either cheaper or R tires -I am *RESISTING* going down that rabbit hole yet once more)!

rnl

When the weather consistently gets in the 40s or below, time for winter tires. I have 20s. Have run 32/39 - partial load pressures until today. When using the 36/44 pressures my rear tires got up to 51psi in hot weather. It's colder now and am running 36/44.

My winter tires at the dealer now and the mechanic recommended that I put them on in November. We live west of Philadelphia.
The November GT Porsche magazine says switch at 7 deg C which is 34 f
I too curious to hear about anyone's experience with the nitrogen fill....curious as air is 80% nitrogen anyway. right? ... trying to remember college chemistry.

chuck911

Well our atmosphere, what you normally inflate with, is already 78% nitrogen. Therefore any benefits of using pure nitrogen per se are bound to be slim. The real benefit to using nitrogen is due to the reduction of water vapor. Compressed air can be quite humid. Moisture that may be vapor when compressed can condense into water inside a cold tire. You measure low pressure and add more moisture-containing air. As the tire heats up this moisture vaporizes, causing pressure to rise much faster than it otherwise would. Bottled nitrogen on the other hand is just that- nitrogen, no water vapor. Other gases could be used to similar effect, but nitrogen is plentiful, cheap and inert.

I run Bridgestone RE-71's and love em!

Edgy01

The nitrogen fill issue is a gimmick for automobiles because "air" is roughly 79% nitrogen anyway. Aircraft use nitrogen because it is moisture free. That's important when your outside air temperature is minus 40º Fahrenheit and at such temperatures moisture will freeze and cause greater issues for you than dry air or nitrogen. Nitrogen molecules are larger than oxygen so there is a theory that the loss via osmosis is less.

I would not run on summer tires much below 45º Fahrenheit because they lose a lot of their resilience as they get colder. Winter tire formulations use other compounds which perform well at 45º and below.

John 996 TT Cab

7' Celsius is actually 44.6' F not 34 F. My sources also tell me minimum safe temperature for the Summer tires is 7'Celsius which is a bit of a problem in Vancouver where our average winter temperature, during the day is around 5-6' Celsius.

I've got a 991S Cab coming as a daily driver and am going to have to think carefully about winter driving. I do have a set of 18" 996 Turbo wheels which I'm going to see if they can be fitted to the 991 for the winter (might need different spacers?). Failing that I guess I'm into an extra set of wheels again.

John in Vancouver

chuckbdc

I have no problems if it is dry right down to 35 F. I do not push it at those temps, but have never had anything feel any different at commuting speeds. Any suggestion of possible of frost freezing rain or snow and its locked up tight in the garage.

Bob Rouleau

Summer tire rubber is at its hardest once ambient temps are around 40 degrees F. Grip is seriously reduced so the off ramp you could take at some speed in summer is likely to bite you once temps are lower.

All season tires are good to - 15 C about 5 deg F and winter tires to -40. The trouble with winter tires is that they wear out very quickly once temps get over freezing i.e. 0 C. So, summer tires are the choice until temps get into the 40's F then use all season or snows.