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?

tks

 

Its actually a lot worse than an ECU fault. With more than 3% tolerance, it can fry your differential. Do a search there are threads about it. I would look at the c4 setup that came with 18s for guideline, but do search a lot on the issue. I think someone here was running an 18 in setup for track?

 

yes i hear you about the diff. others have mentioned this. when i look at the C4 set up the difference is very similar at 0.73 taller in the rear. So it seems like the need to stay close to this.

 

May I ask why you want to go with an 18 set up?

 

cheaper running cost at track.

 

Thats what I thought.....

 

finding a set of 18inch wheel that has 380mm rotor/caliper clearance is also another subject to consider, but very interested to see if you find a working solution

 

Already done. Clears.