[quote]Originally posted by Viken:
<strong>Me? Oh, I drive like a granny. </strong><hr></blockquote>

So you find that those lower pressures work out much better for you when you make those right hand turns at 7 mph, do ya?

And just so EVERYONE stays on topic, the original poster asked for STREET cold air pressure, not at the track! <img src="graemlins/nono.gif" border="0" alt="[nono]" />

 

[quote]Originally posted by dcpmark:
<strong>And just so EVERYONE stays on topic, the original poster asked for STREET cold air pressure, not at the track! <img src="graemlins/nono.gif" border="0" alt="[nono]" /> </strong><hr></blockquote>

Well, I don't know about the rest but my "street" (not R-compound) tire pressures do not change between STREET and TRACK. As such, I maintain pressures of 32 and 35 front and rear. I'd probably go down to 34 rear on a RWD car, though.

 

I'm with Chris, Viken, and Greg. I originally tried those insane Porsche 36/44 recommendations, but now run cold street pressures of 32-34 front and 34 - 36 back, using S-02s, S-03s, and now my much improved Pirelli P-Zero C's. Never dented a wheel.

During last year's DE season with the S-02s, starting with 32 front / 34 rear consistently gave me 40 psi all around after a session, which seems just right.

If you like the rear to feel like it's on ice skates, 44 psi is the way to go.

 

[quote]Originally posted by Viken:
<strong>Well, I don't know about the rest but my "street" tire pressures do not change between STREET and TRACK.</strong><hr></blockquote>

Well, I have exactly 0 hours of track experience, but to me that doesn't seem to make any sense. On the track, you are adjusting tire pressure because you are pushing your car to its limits, no? Tires can heat up fast and even overheat. You adjust tire pressure accordingly to compensate AND to achieve the highest possible control at handling limits, or to achieve a particular style of control at the higher limits. No one drives like that on the street/hwy, are they? Is anyone driving their 993s to the limits on streets, or are we commuting, going out to dinner, driving to Starbucks, the dry cleaners, avoiding potholes, etc.?

I am not aware of any place in Los Angeles where I can push my car anywhere near its limits without endangering myself and/or others. The biggest thrill I can get is on the way up the freeway onramp and a good downshift on the offramp. Sure, I love that feeling of taking a clear curving offramp at 60 rather the recommended 35mph, but I'm not putting the car even close to its limits.

Viken, am I wrong in my thinking? <img src="confused.gif" border="0">

 

Mark,

You are not wrong in the way you are thinking if you do not push your car on the streets. However, 36/44 is still not a preferred pressure set even for those who cruise on the highways. Try lowering yours to 36/38 or somewhere around that and see how much better the car will feel.

 

[quote]Originally posted by Silver Bullet:
<strong>Can't express it properly but I felt "wobbly".</strong><hr></blockquote>

Kim,

If you felt wobbly, it might not be related to your tires! (Sorry, I couldn't resist!)

Maybe, those pesky RSR mufflers are affecting your car's performance. You know - they are made by some backyard hack.

 

[quote]Originally posted by Silver Bullet:
<strong>Also, I bet if I bought an air compressor from the right vendor and filled the tires, I would get an 10-15HP increase too!</strong><hr></blockquote>

Don't forget that tire pressure gauge. They are not all that accurate, you know.

 

[quote]Originally posted by Viken:
<strong>Try lowering yours to 36/38 or somewhere around that and see how much better the car will feel.</strong><hr></blockquote>

Actually, I did get to try it for a while when I bought my car. The previous owner was running SO2s at 32/38, and both of the rear wheels were slightly bent. This from a guy who lived and worked in Beverly Hills, which is not exactly known for its rough streets! I immediately went to 36/44, and was treated to a bone-jarring ride. Hence the switch to Pilot Sports.

I'm scared to try it with my Pilot Sports for two reasons: first, the immutable laws of physics say that there is a greater risk of bending the wheels at 38 than there is at 44. The less pressure in the tire the more give in the sidewall, and the greater the chance that one good pothole will send one of my wheels to the shop. Now, I'm not saying that it WILL happen, as you and Anir and others can attest to, but only that there is a greater risk. Of this fact there can be no debate, that lowering the tire pressure increases the CHANCE of a bent rim from the street.

It seems that there are two camps here, people who have had rims bent that now stick to 44psi, and people who have never had a rim bent while using much lower pressures. Would the latter people feel the same way if they had bent their wheels, and it could be shown that the damage was directly caused by the lower pressure? By analogy, Viken, let's pretend I said that "I always lock my front door because once I got robbed," and you said that "I never lock my front door and I've never been robbed." Don't you think you might change your tune if you did, in fact, get robbed one day because you left your front door unlocked?

By the way, can you all tell that I have way too much free time on my hands at work today?

Oh, and the second reason that I'm scared to try it is that I might like it.......

 

I have 18" Turbo Wheels with P-zeros and am 34-35 cold front/37-38 cold rear.

I was at streets of willow a few weeks back and took the fronts down because they were so hot and so was the track surface. Once they cooled (later that night) they were around 30/32. I think I was getting 5-6lbs more when they were hot.

BTW I also live in LA and there ARE a lot of places where you can push the car and do so safely.

 

[quote]Originally posted by dcpmark:
<strong>By analogy, Viken, let's pretend I said that "I always lock my front door because once I got robbed," and you said that "I never lock my front door and I've never been robbed." Don't you think you might change your tune if you did, in fact, get robbed one day because you left your front door unlocked?</strong><hr></blockquote>

No, this is not a fair analogy. I used to bend wheels all the time when I was younger and always bought crappy aftermarket wheels. I also used to drive like a maniac and never paid attention to potholes or other severe road irregularities. With higher quality such as Porsche's OEM and more mature and attentive driving comes straight and true wheels.

[quote]<strong>Oh, and the second reason that I'm scared to try it is that I might like it.......</strong><hr></blockquote>

You are afraid of liking a properly behaving Porsche automobile???? Quick, trade it in for a Lexus. That will surely take the skepticism and scare away in an instant.

 

[quote]Originally posted by 88clbsport:
<strong>BTW I also live in LA and there ARE a lot of places where you can push the car and do so safely.</strong><hr></blockquote>

Absolutely!

 

[quote]Originally posted by 88clbsport:
<strong>I BTW I also live in LA and there ARE a lot of places where you can push the car and do so safely.</strong><hr></blockquote>

Clubby, don't be such a tease! Where??? <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" />

 

Although I have not bent any rims, I look at my tire pressures differently between street and track. For the track the tire temps get much hotter than on the street, thus causing the pressures to increase. I found that I had to lower the pressures regularly, as the car got very "darty" with the hotter and higher temps. I tried to keep them at 34-35 front and 38 rear hot. As they cooled down, they went to 30 front, 34 rear and on the street I was concerned about the bent rim issue. I increased the pressures to 36 front and 40 rear. Seems to be a nice comprimise and the car does not feel darty (as it did at the factory settings). I don't drive the car very hard on the street though, as it is mostly commuting to work. Maximum street performance is secondary to me preventing a bent rim.

 

Hi all:

Kim: My alignment on both cars (one with 285x30x18 the other with 265x30x18) was factory, although I did not have it checked on either as the problem went away as soon as I let about 8 psi (they were pumped up by the local dealer after a service). You'll have a better feel for how minute changes in tire pressure impact your contact patches on this car after a few days on the track!

With 44 psi the rear feels like it is tramlining--following non-existent grooves in a non-existent headwind--at highway speeds. Not reassuring.

Viken--interesting point about new rears and worn fronts, could have been the case on my 1997.

Someone asked Bruce Anderson about this years ago (Pano?)... and he thought the 44 psi was ridiculous. As I recall he recommended 2-4 psi difference front to rear.

My car handles great on 34/36, with no cupping. I gradually drop the pressures about 6 psi during hot track days--after which you'll have so much race tire snot on your tires you'll think you've bent all 4 wheels anyway!!

(gotta get some track rubber)

 

1.Will the same principals apply to 17"???

2.Why there is a major difference it the rear tire presures between an 18" and 17" as Porsche recommends 36 for rears on 17"?

3. Why DE instructors constantly recommend to inflate from cold at least 2 psi over the recommended manufacturers pressure?

By the way from my experience on the track I agree that really high pressures has caused the back end to be very loose. I have not however tried anything below 36 psi cold.