ClayMan28

A beast like the 993TT deserves as much wheel and tire as it can get. I'm looking at an opportunity to rebuild a set of 3-piece wheels and I'm dreaming up the possibilities, so would appreciate some veteran advice about fitment, fender (outboard) and suspension (inboard) clearance! (Let's assume they fit over the big reds)

In the front, I'm looking to fit 235/40-18 or 245/40-18 street tires (e.g., PS2):
18x9 +50 (conservative, should work unless it hits something inside?)
18x9 +37 (aggressive)
18x8.5 +43 (plan B - would prefer 9" wide)

In the back, I'd be using 315/30-18 tires (e.g., PS2):
18x11.5 +44 (easy, right?)
18x11.5 +32 (aggressive)
18x12 +38 (crazy?)

Thoughts? In the aggressive / crazy scenarios, how much negative camber would be needed to safely clear the fenders (let's assume they are moderately rolled, maintaining original contour / shape)?

wagongotya

Do you already have the wheels? What are the offsets, widths, and barrel sizes currently? I assume this is a street setup with street tires? That's going to highly limit the agressiveness of your alignment if you want to keep your tires longer than a few thousand miles.

In terms of what fits...9.0x18 and 11.5x18 is as big as you really need to go to stuff 245/40/18 and 315/30/18 respectively. Not sure how much lip you want to run but around ET45 and ET35 seem to be pretty standard with the 9 and 11.5 inch widths.

I hope that helps.

Basal Skull

For reference I have 255/35 on 8.5x18 offset 52mm, and 315/30 on rear 11x18 offset 40mm , -2 all around (gt2 uprights). The higher profile fronts rub on the liners at full lock and I've gone through liners. I think the 35 profile is better for the fronts but have modified my liners as well.

ScottMellor

Liners? We don't need no stinkin' liners!
I had to remove mine altogether. But obviously I have flared fenders and ginormous wheels.

ClayMan28

Interesting, and your centre diff is OK with the rears being ~2% larger than the fronts? (Stock 225/40 and 285/30 is ~1.4% *smaller* in the back)

DM993tt

Anything under 4% is supposedly OK

I ripped out my front diff

DM993tt

I thought anything under 4% rolling circumference is supposedly OK

I ripped out my front diff

Basal Skull

What Dave said^
I think it's still okay, with all 4's off the ground spinning one wheel seems to turn the others but who knows? It didn't help me much few weeks ago when a bunch of us got caught in a 'flash' snow storm coming back on I5 from a track day... was chugging along so slow in 6th and started to go uphill I decided to shift down, which was enough to unsettle the car, I spun out twice on the freeway, pretty scary - didn't seem like 4wd was helping me a bit but we all made it home without any other incident.

ClayMan28

I also have the option if 18x9.5 +44. Anyone successfully run 18x9.5 or in the front? Particularly with 255/35 tires? What offset? (Or 19x9.5)

Apparently this has been done on 996s with just rolled fenders, no flares.