I need suggestions for a good 18 inch wheel and tires. I'm liking the Volks but I'm on the fence. Any ideas?

 

Did you look at the tirerack site?

 

I have a set of CCW C14s: http://www.ccwheel.com/files/home.php

 

Wheel choice is up to you but be careful with tire choice, especially the rears. Fronts at 235/40/18 keep the same rolling diameter but 295/35/18 (or 305's) are required for the rear to keep a 660mm (26") rolling circumference. I made the mistake of getting 285/30/18 which are at least an inch shorter than the OEM 295/30/19. (much harder to find R-Spec semi slick rubber in this size as well).
the rears (on 285/30/18) were actually smaller than the fronts which set off my PSM light a few times. I've since changed to the right size tire and no more problems.

 

Trust me on this....

CCW Wheels
9x18 front
12x18 rear

Toyo R888
255/35/18 front
315/30/18 rear

this combo work extremely well for the track.

 

what about porsche factory 18'' wheels ?

 

I ran 997 18" wheels for my first track set up, went with the 295/30/18 in the rear and they were way too small when compared to the stock tire height. I didn't have any PASM error's but it didn't sit well. The right combo would have been as mdrums suggested a 315/30/18 gives the corrrect height, however the 10" wide wheel that comes from Porsche is too narrow for the width. You should have at least a 11" wheel, but a 12" wheels is better.

I now run 19" with MPSC, and love the way the car handles, but I am limited to 4 tires for the track and they are a little more more for the tires.

 

To keep everything the same for a 997 S with 18" wheels, wouldn't the specs have to be"

Front: 235-245/40/18
Rear: 295-315/35/18

Don't you have to increase the sidewall size to account for the loss in 1" diameter of the wheels?

This is what i was told by Porsche, Kumo, and mechanic.

So Stock side-walls are: Front 35 & Rear 30 so you would have to go with Front 40 Rear 35.

 

I used the tire calculator at 1010tires.com to compare the sizes suggested:

Seems like the best fit would be the 235/40 & 295/35 .. I read that PASM has issues when the rolling diameters between the front and rear are not in sync (could be regarding C4/C4s).

 

I put the factory 19 in back with the RINSPEED in front and drove 1000 mile ( Denver to LA ) without any errors. I think it's just C4 and C4S

 

What size tires do you have on your rinspeeds? If its 235/30R20 .. then there is only a .1in difference between them and the 235/35R19.

 

Spot on Mishref.
The comparison from 1010tires confirms exactly the issues I've experienced from having the wrong rolling diameter.
See attached picture...
To see the difference, the standard 295/30/19 on OEM 19" Lobsters is the tire on the right (PS2). The track tire 285/30/18 on an 18x10" wheel is on the left.
Clearly the OEM tire on the right is "taller" than that of the 285/30/18 or the right.
My OPC commented that C2's and especially C4's would have PSM/ABS issues if the front and rear rolling diameters dont match that of the OEM setups.
Also, since changing to 295/35/18's with larger sidewalls I find the rear tracks much better than before with a more progressive feel. Just MHO.