BimmFiniti

Thanks! Appreciate it. I really love the combination of performance, looks and driveability (although you might not think so given this thread!).

You're right that it is the OEM wing. I just don't have the offical name for it: everything else was on the original window sticker; the wing was added afterward.

I'm not quite sure what I'll be doing yet with my setup. Maybe something's wrong, maybe I'm just expecting more of a BMW ride, maybe I need different tires? Stay tuned...

Mathemagician

OK, now you've done gone and confused a rookie!

If 36 front and 44 rear sets up a lot of understeer, that should mean there is a lot less grip in front and a lot more grip in the rear. Doesn't it then make more sense to correct this by giving the front more grip (i.e. raise the front pressure towards 44) rather than taking grip away from the rear (i.e. lowering the rear pressure towards 36)?

CosmosC4S

Wait...doesn't more air pressure create less rubber grip, and less air = more grip???

LJpete

What suspension are you running? I have stock suspension and 18's with PS2's and the ride is way better than any BMW I have had or driven (and I've had a chance to drive many ranging form E30-to E92 and everything in between). My 996 is easily as comfortable as my 98 323is with normal (non sport suspension). BMW's especially the sport suspension package, are always over damped on compression which gives them a harsh initial hit even though they have relatively low spring rates.

How old is your suspension? Your dampers could be shot which is giving you the bad ride. Mines a bit on the old side and I still find the car controlled and comfortable. It' has a bit too much body roll for my tastes but considering it's stock it's not bad.

I suspect something else is afoot here.

sjfehr

Generally speaking, the lower the air pressure and bigger the contact patch, the better. (Tire rubber has a dynamic coefficient of friction that decreases with pressure; if you push on it twice as hard, it grips more, but not twice as much.) Other factors come into play, though, such as sidewall stiffness and tire deformation, so simply bleeding air doesn't work out all that well. Optimum tire pressure is on a curve with a sweet spot. Too little air, and tires lose grip. Too much air, and tires lose grip. (Generally, too much air is less detrimental than too little.) This changes when you compare cornering grip to accelerating/braking grip. And from one model tire to another.

Logic dictates Porsche optimized the front tire pressure for braking, and rear for cornering, to ensure nice safe understeer. Which is nice and safe for street use, but not so good for performance handling.

BimmFiniti

Just a quick update. I took my car into Les Schwab today and they did find the left front wheel was imbalanced.

I'm running my tires @ 33/42 now, close to the 36/44 that's recommended.
* I think I might be able to go to 36/44 with PS2s, but not with the T1Rs.
* Around town - which has always been fine - is still OK.
* On the highway... well, we'll see. I'll update next time I take a significant highway drive to see if the wheel balancing has improved the situation.