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Front + Rear 18x12 trials and tribulations

neema

TMO Race
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Location
Fresno, CA
Figured I'd share in case anyone else wants to go down this avenue. I think most people know the "why" you go down this avenue. Anyways, I'll cut the crap and get to details.

I currently use 305/35/18 NT01s, which is a ~26.3" OD. Haven't tried taller OD tires yet.

Wheels are Forgestar CF5s, et38 up front and et58 in the rear, or notably, 8" backspace in the front and 8.78" in the rear. My MO was to mount wheels as tightly as possible to inboard obstructions and use spacers for wider tires as needed. These wheel dimensions fit with very, very little clearance between inboard hardware, which is great! Use 3, 5, 7mm spacers as needed for tires. Note: I'd probably do 1mm less offset (et37) up front. I didn't have any issues driving around town, but on track, I took a little paint off the strut. I now have a 3mm spacer up there.


If you wanted identical wheel sizes on all four corners, 18x12 et58 wheels with a 20-25mm spacer should do the trick


Wheel clearance steps by axle:

Front:
  • Cortex offset struts
  • you may need to trim or use spacers on the swaybar endlink
  • camber plates (presumably you have these if you have Cortex struts). I have 2.6°, limited by the camber plate, not by the hole in the strut tower. More camber would probably allow for a 335?


Inboard clearance with no spacer

IMG_7012.jpg

What it looks like outside
IMG_7026.jpg


Rear
  • bump stop bracket trim/removal and either bump stops relocated or bump stops on rear shocks
  • Stock, or as close to OEM rear shock style mount. If using Cortex rear coilovers: 1. divorce the spring and put on a weight jacker in the OEM location, 2. invert/flip the shock upside down, and 3. ideally remove spring perches. You can avoid spring perch removal (like me) and run a 10mm spacer, but now you're dealing with some rear tire protrusion. I don't rub but have since ordered rear JRis with OEM style mounts, rather than eyelets, to make adjustments easier (in the trunk rather than under the car) and open up more room
  • properly centered watts link
  • with a shorter 315/30 or 335/30, you may be able use a small spacer and OD

With an OEM style shock, I may have been able to pull in the rear wheel a few more mm, but on 18s it gets tough since the rim gets close to the top of the shock mount. 20" wheels can usually go to et61 because the wheel is hanging out in slightly different parts of the wheel well.


Some photos of the inverted rear shock that I have. You can see the spring perch still in place that takes up a little space. Disregard the bump stop on the axle. I run mine on the shock
IMG_2684.JPG


Still affords a little more space than how Cortex runs the coilover out of the box, like the image below.
IMG_2145.JPG


What I'm changing to:
IMG_7028.PNG


How the car sits now:

IMG_7021.jpg
IMG_7024.jpg
 
Last edited:

neema

TMO Race
Messages
431
Reaction score
109
Location
Fresno, CA
How I manage to still mess up image hosting blows my mind. Fixed links. hopefully it works
 
Last edited:

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