Has anyone put on 18s?
I'm thinking about going to an 18in wheel/tire set up. There are plenty of wheel choices, however tires are a different story.
The challenging part is finding the right height combo as not to trip any ECUs.
Let me explain. The stock set up is:

F- 235/35/19 = 25.48"
R- 305/30/19 = 26.20"

Difference of 0.72" taller in the REAR

18" Option A:

F- 245/40/18 = 25.72"
R- 315/35/18 = 26.68"

Difference of 0.96" taller in the REAR

So option A yields a .24" taller rear. Will this trip the ECU/traction control on our AWD cars?

 

305/35/18 rear I run and IIRC the Fronts are 245/40/18

Keep it around .7 front to back

 

I would only run 18s in track or snow tires, be sure there is <2% difference in dia or the diff is a gonner.

 

With my earlier M3, I went to 19 from 18 and ride was much too stiff. So for this reason, thought 18s for my turbo would give same result. However, 3 tire/wheel dealers all said that Porsche suspension was set up for 19s (excluding snow tires) and consequently ride would be same except for more side-to-side in sharp curves. Also the look changed. A couple 6speeds have posted photos of 997s with 18s and I liked the 19" look much better.

 

just installed my 18" today to try it next weekend's track day .. i went with pirielli trofeo 295/30/18 and 235/40/18 .. but when i took the car for a test drive today , there was a problem with ABS ... my tuner said it just needs remapping in the software and everything would be normal then ....

would remapping solve this problem ?

 

this is good to know. However looking at my the calculations, your set up is:

235/40/18 = 25.40 in
295/30/18 = 24.97 in

difference = 0.43 in SHORTER Rears.

was there any reason you went w/ 30 series, vs 35series on the rears as the 35's would have yielded a stock difference of approx 0.73 in TALLER ?

tks

 

thank you for the information ...

30 series was the only available option from pirielli trofeo for the 18" , i know i did a mistake and i've should have bought toyos r888 instead as they offer a 35 series in their 18" range . any way , my tuner said the problem cannot be solved by doing a remap for the software.

 

according to tirerack.com that size combo isnt available. are you running different brand/models f/r?

 

im running TROFEO for the rear and TROFEO R for the front.

any way i decided to stay with the 19" wheels, as the 18" plans did not go well after all . BTW im going to sell the trofeo tires i hvae now in 18" , i have 2 sets of 235/40/18 trofeo r and 295/30/18 trofeo , one set was used for few hours and the other set is still brand new .... if anyone is interested let me know..

 

take'em to the next track day event. They will sell.