cleanme

Out of pure curiosity, say you had Michelin 'X' tires and 4-18" rims and 4-19" rims. Wouldn't the 19" rims& tires work better because of a bigger contact patch?

multi21

I'm wondering that as well as it seems logical that the 19" have larger contact patch. I understand a lot of 997 GT3 owners are going to 18" for track use for less weight. Is the larger sidewall (softer) on the 18" contribute to better grip in the rear?

Ray G

Good point, but no, my tires are naked.

spr10r

I remain convinced that the contact patch area is fundamentally a function of the pressure in the tyre and the weight on the wheel. Generally, the lower the diameter, the lower the running presure and the greater the contact patch. The shape of the contact patch is related to the width, and wide tyres typical of a large dia. get closer to an ideal circular patch: The shape of the patch is generally more key than the actual area.
On flat surfaces i find it tough to loose grip at the back without judicous right pedal, but at cold 36psi+ rear it skips on bumps in an excitring way.

rop3

This is starting to concern me, I have an 08 RS on order great car to look at but what good is it if you can't track it with confidence. They are supposed to be track focused production cars?

See my other post video spins @ Limerock many owners are spinning/crashing there brand new cars?

I hope there is a fix for this.

mooty

you just need the normal mpsc tires and you be fine.
911 is intrinsically challenging to drive, that's part of the fun.
test it out, change alignmentment, play with tires....

atomic80

I don't think it'd be possible to go with 18" wheels in your case since you have the PCCBs with the 380mm rotors up front. 18" wheels won't clear those.

rop3

That's a great color 993, Ocean Blue?

frayed

Haven't read carefully through the replies. However, my first track day with my car and I was disappointed as the rear was a twitchy *****. Very daunting. But puckering in 90 mph corners.

Until I really pushed the car hard and after some hot lapping stressing the tires and managing pressures did the grip 'come in.' From that point on, it felt exactly like I expected. Sub-hoosier grip but with perma-grin g-force ear to ear grins.

My theory: street miles harden up these MPSCs and they need to be scrubbed in pretty hard on track before they come in. But they will, but it takes a good bit of abrasion and heat. These tires are not fast out of the box after notable street miles.

leif997

Dude....what's your point and how do you come in here cracking like that?

Ray G

My alignment was checked, and it was good. It's now set to the recommended track setting from the manual. I am also having a new set of tires mounted. I will be going to the track July 4th to test out the setup. I have a theory that it is the tires. For whatever reason, the more laps, the slippery they got (even when adjusting pressure down). If it were a suspension problem, it would not change from lap to lap. The tires behaved just like heat-cycled out rubber. Maybe I got an old set, or driving on the street altered them. I don't know, but I'll check back after July 4th.

NoSubEDU

Would be interesting to see if my Pirelli's offer any relief on this matter? Guess we'll find out this weekend- I'll be at Lowe's.

crispenigl

I said it in a post 2 months ago when I came back from button willow and described how greasy my back end was on corner exits

i learned that my tire pressure was too high and that my sway bars were off.

i dropped pressed to 28/30 at the start of a session and let it build to 34/36 and it was much better - i also softened the fronts and stiffened the rear.

i have had better luck since then but it still wants to step out more than i would expect under throttle exiting a corner.

Greg

crispenigl

interesting observation - i have noticed that my tires do get better with wear during the end of the track days as well

mooty

that is true, but even then it's not that grippy. and now my tire is all done.