FixedWing

[quote]<strong>I am going to put helium in my street car - less unsprung weight.
</strong><hr></blockquote>

Not true!!!

Well, I am sure there is a specific gravity difference between helium and air but the idea that helium will just make everything lighter doesn't work. Helium must be accelerated up or down and around and around just as air does.

To prove this consider a blimp. Have you ever seen a fast blimp?

S.

Fadz

[quote]Originally posted by 02-targa911:
<strong>Fadz,to answer ur first quistion on how much pressure to put. I'm not far off from u in Bahrain and I usually put 32 front and 40 rear. Works for me </strong><hr></blockquote>

What you mentioned is reasonable as long as the size of the tyres are front 225/40 and rear 295/30??? Do you have the same tyres size?

One more thing since you are in Bahrain, do you think i can find a clean 964 cabrio out there?

Thanks

Fadz

[quote]Originally posted by Greg Fishman:
<strong>

Actually your pressures are way, way off. Lower the fronts by abour 3 or 4 psi and the rears by about 8 and you will have a much better riding and handling car.</strong><hr></blockquote>

Greg, do you think the extra pressure in tyres made the vibration of the steering wheel?

Thanks

Greg Fishman

[quote]Originally posted by Fadz:
<strong>

Greg, do you think the extra pressure in tyres made the vibration of the steering wheel?

Thanks</strong><hr></blockquote>

My guess is the tires had a slight flat spot from sitting. It usually goes away after driving for a distance, and getting the tires warm, also depends on how long the car has sat. Pirelli's seem to be worse for this than other brands I have had

RogerJ

[quote]Originally posted by Karl S:
<strong>Air generated by a compression always has some water in it. The water molecules will heat and expand, causing the tire pressure to increase significantly between cold and hot temps (8-12psi), especially with extreme use as on a track or at high speed on the autobahn.

Nitrogen is dry, assuming you get your tank from a good dealer who purges the tank properly before filling it. Because there is no water vapor in it, the hot pressure does not increase nearly as much, thus as others have pointed out, the hot pressures will not dramatically change from cold (2-4 psi).

Karl</strong><hr></blockquote>

Others here have dealt with the theortical so I will only relate my personal experience. I started carrying N so I could adjust my Penske shocks. I believe that is how the whole N use in tires got started - you had a ready source of gas to add a little pressure to tire. Once I started doing this I thought it would be cool to run all N in the tires are that is what the Indycar guys were doing. Now admittedly I had no way to evacuate the tire completely. I just let all the air out and refilled with N, so there was a small amount of air with a trivial amount of moisture in it.

My experience was quite different than quoted above. The pressure rise was quite similar when using plain ol' air. I think others on this thread have explained way quite well. Race tires seem to seep a little air when they are unused and I didn't notice any change in that behavior.

In asking around about this, I was told (by the tire guy for the Ganassi team) that the real benefit is that because N is dry they get a more consistant pressure rise when they use from humid conditions vs. drier ones. Since they change pressures regularly by as little as half a pound, they feel there is a benefit. The benefit is in the repeatability of making the car handle a certain way with certain settings.

In closing, I don't see any benefit at all in running N in a street car. With that said, it certainly won't hurt anything either.