Change of tires radically change the car...

[deschodt]

I inherited Pirelli P-zeros when I bought my 03 C2. I had nothing against Pirelli...until I drove the car more than 5 minutes, and in truth, maybe it's unfair from me, maybe those particular tires were a bad batch, heat cycled wrong, whatever... But I never quite liked my 996's road feel until yesterday... I thought the tires were incredibly loud, road noise and "doinks" reverberating inside the cockpit whenever the rear tires drove over a road reflector, harsh (even before the ROW 030), and most annoyingly, took a flat spot just from sitting overnight... and did I mention loud ???

I finally picked up a nail and drove on the tire long enough to do some damage (can't feel a flat on those low profiles unless you're on a twisty road, or maybe it was my subconscious making sure I destroyed the infamous "squirelli" tire) ! I was not replacing just the rears to be stuck with more Pirellis, so I picked up a set of 4 Michelin Pilot sport N-something. Not cheap, ($1500 dealer installed) but last time I went cheap I got a set from tire rack and one was out of round, so my car was stuck for a week waiting for an exchange!!!

Wow... Initially it was so-so until I remembered the dealer probably went with 36F/44R Hindenburg pressures again. Once I went down to more normal pressures (34/38), what a difference! Quieter, softer ride, more shock absorbtion, already better grip (and they're not even worn in) - I enjoy the ride a lot more ! I gotta say that the 996 is quite the resonance chamber, though. Any expansion joint or grooved asphalt and the whole cabin reverberates "doink" sounds like crazy... I wonder if it's just mine, but it did it before the ROW030 too. Maybe it's the extreme low profile tires, I ran 18s on previous porsches (40 profiles), but never 30s... I'm starting to think a 30 profile is just plain too harsh for my tastes, generally speaking, and not all that much better on track!

Anyway, if you're on those pirellis and never tried anything else, do yourself a favor and try another brand! My car is 10x better now (and the Pirellis were not even worn out when deep sixed).

Edited December 4, 2007 by deschodt

[KevinMac]

[Everthing I have read was those pressures were done based on the Porsche recommendation after test track runs for the best handling. When you reduce pressure the sidewalls flex more.

[deschodt]

[Everthing I have read was those pressures were done based on the Porsche recommendation after test track runs for the best handling. When you reduce pressure the sidewalls flex more.

I'm generally not one to argue with Porsche, and definitely am not arguing with you either, but in this case, let me state that:

- on 44R, the car is downright bouncy, the tires have zero give and I feel like I'm riding on balloons.. That's the highest pressure I've heard of too, for that kind of size

- On 44R, the pressure quickly rises to 50+ after a couple of laps, and I think that's getting downright dangerous. Most track guys reduce those pressures greatly and then beat the crap out of the car for laps and laps, so it can't be that bad for performance ! before I realized this, I noticed that my tires were going away after 15 minutes or so. So clearly, 44 is not good for performance any way you look at it...

- The 987 with similar(ish) tire sizes in 18" lists 32/36 as the pressure. The 993 was also lower... the 996 in 18" is the first time that ludicrous 44 ever appeared that I know of ? Except maybe your space saver tire ? ;-)

- I've read that those high pressures were not so much for handling as they were to protect the rim from potholes...I can believe that as my car came to me with 2 bent rear wheels...

- a 30 sidewall is *very* stiff... It took me 10 minutes too long to notice my 40 sidewall tire was flat on the 987. I drove my 996 on 30 profiles on a flat rear tire for 40 miles (straight, admittedly) without noticing it was flat, or getting flat, from the handling. I think a 30 sidewall is plenty stiff no matter what ;-) It's almost a run flat !!!

- Final data point, that's the biggest gap Front to rear I've ever seen on a 911.. Most 911s over the years have been happier with say a4 psi gap front to rear, this is 8 !!!

Just throwing that out there, for the sake of discussion ;-)

PS: Could be wrong on this but I believe I've read that 44 produced an abnormal wear pattern as well

Edited December 4, 2007 by deschodt

[martadon]

I inherited Pirelli P-zeros when I bought my 03 C2. I had nothing against Pirelli...until I drove the car more than 5 minutes, and in truth, maybe it's unfair from me, maybe those particular tires were a bad batch, heat cycled wrong, whatever... But I never quite liked my 996's road feel until yesterday... I thought the tires were incredibly loud, road noise and "doinks" reverberating inside the cockpit whenever the rear tires drove over a road reflector, harsh (even before the ROW 030), and most annoyingly, took a flat spot just from sitting overnight... and did I mention loud ???

I finally picked up a nail and drove on the tire long enough to do some damage (can't feel a flat on those low profiles unless you're on a twisty road, or maybe it was my subconscious making sure I destroyed the infamous "squirelli" tire) ! I was not replacing just the rears to be stuck with more Pirellis, so I picked up a set of 4 Michelin Pilot sport N-something. Not cheap, ($1500 dealer installed) but last time I went cheap I got a set from tire rack and one was out of round, so my car was stuck for a week waiting for an exchange!!!

Wow... Initially it was so-so until I remembered the dealer probably went with 36F/44R Hindenburg pressures again. Once I went down to more normal pressures (34/38), what a difference! Quieter, softer ride, more shock absorbtion, already better grip (and they're not even worn in) - I enjoy the ride a lot more ! I gotta say that the 996 is quite the resonance chamber, though. Any expansion joint or grooved asphalt and the whole cabin reverberates "doink" sounds like crazy... I wonder if it's just mine, but it did it before the ROW030 too. Maybe it's the extreme low profile tires, I ran 18s on previous porsches (40 profiles), but never 30s... I'm starting to think a 30 profile is just plain too harsh for my tastes, generally speaking, and not all that much better on track!

Anyway, if you're on those pirellis and never tried anything else, do yourself a favor and try another brand! My car is 10x better now (and the Pirellis were not even worn out when deep sixed).

2001 C2 w/18" rims, here. P-Zero Rosso's came on the car and I agree that they're the loudest things ever. Very sticky on the pavement but wear-out like pencil erasers. I now have Bridgestone Potenza RE960AS Pole Positions and can tell you they are FAR superior for my tastes. Quiet, handle well (no track, open road) and good cost factor.

I keep mine at the recommended tire pressures and everything is still nice and quiet (relative to the Pirelli's). I'd be a little leery of running too low tire pressures unless all of your driving is on ultra smooth, new pavement. Wouldn't want to bend a rim--35 profile tires place the rim mighty close to the road!

[deschodt]

>Wouldn't want to bend a rim--35 profile tires place the rim mighty close to the road!

Yes they do ! ;-) Like I said I had to buy 2 after trying repeatedly to balance my rears ... $1400 I think !

This is probably the last car that I buy with such a low profile tire... I do quite a bit of track events, and I enjoy sharpess over comfort, but in my opinion 30 profiles cross the line. 40 is as low as I am comfortable with these days, and not much of a performance hit... Nothing wrong with a little sidewall flex here and there, it's more predictable anyway ;-)

[martadon]

>Wouldn't want to bend a rim--35 profile tires place the rim mighty close to the road!

Yes they do ! ;-) Like I said I had to buy 2 after trying repeatedly to balance my rears ... $1400 I think !

This is probably the last car that I buy with such a low profile tire... I do quite a bit of track events, and I enjoy sharpess over comfort, but in my opinion 30 profiles cross the line. 40 is as low as I am comfortable with these days, and not much of a performance hit... Nothing wrong with a little sidewall flex here and there, it's more predictable anyway ;-)

You could always go with 17" rims. They're 50/40 profile, front/rear.

[deschodt]

You could always go with 17" rims. They're 50/40 profile, front/rear.

Thought about it, but I think that limits you to 265 rears...

[Izzy]

I would be surprised if the 36-44 pressures where done post any kind of tracking. I made the mistake last weekend, inflated my track tires to drive to VIR to 36-42. Saturday morning I was talkng to friends in the paddock and heard the call for my group, got the helmet on and drove to the grid. Air temp was around 41F. After abour 5 laps, having a difficult time turning, realized that I forgot to lower my pressures pre-track. The car drove like a pig. I kept going but slowed down to turn.

Got off track, and measure the pressure to be 45-53, zepelin pressure. Lowered to 32-37 hot, and the next track time the tires had a grip like a 4 year-old on a Sponge Bob movie. I use the Falken Azenis RTs, 275-35-18's rears work fine for me.

[der meister]

I would be surprised if the 36-44 pressures where done post any kind of tracking. I made the mistake last weekend, inflated my track tires to drive to VIR to 36-42. Saturday morning I was talkng to friends in the paddock and heard the call for my group, got the helmet on and drove to the grid. Air temp was around 41F. After abour 5 laps, having a difficult time turning, realized that I forgot to lower my pressures pre-track. The car drove like a pig. I kept going but slowed down to turn.

Got off track, and measure the pressure to be 45-53, zepelin pressure. Lowered to 32-37 hot, and the next track time the tires had a grip like a 4 year-old on a Sponge Bob movie. I use the Falken Azenis RTs, 275-35-18's rears work fine for me.

A bit off-topic, but have you ever tried Nitrogen in the tires?

http://www.sonic.net/~racerx/excellence-ma...rt1/art1p3.html

[Izzy]

PV=nRT

Long discussion on nitrogen on this thread

http://www.renntech.org/forums/index.php?s...amp;hl=nitrogen