They do make a 305 for 18s. I run them. 245/40/18 and 305/35/18. Fantastic set up and grip is better than the smaller 315/30 due to the larger contact patch and better load rating. RWD set up though...

 

^yes. i meant they didnt make a 305 30 18 (so he could stay within the awd parameters with a 235 40 front)

 

Gotcha. I used to run a 315/30/18 as my track tire and was really shocked how much better the 305/35/18 is. Better grip, less rollover. Same exact brand, just different size.

 

i can understand why. more sidewall is more grip.

these awd guys man... they dont know what theyre missing lol


997 cup cars run 18s to take advantage of a thicker sidewall

btw, how did it affect acceleration ? i always thought the bigger you go, the slower your acceleration would be.

 

Ok, Steve, Prodigymb, and Powderhound... I've ordered 18x9 at 40 offset and 18x12 at 40 offset wheels. On H&R springs, not coilovers, this will run 235 and 315's? What sidewall again? One last time please.

WhereItsAt

 

If anything, in my case acceleration improved based on the speeds I see at the end of the straight at our track, basically 145 v 142mph I saw before (and this is based on GPS speed, not speedometer). The higher Hp cars will see a benefit because they have the power for the taller gearing. These speeds are measured via GPS. The one byproduct of the 26.4" tall rear is the fact that my speedo is pretty much on the money with actual GPS speed. With the shorter 315/30/18 my speedo indicated about 3-4 mph fast.

 

Those are good offsets. I run 18x9 et47 and 18x12 et41. My fronts track is widened 10mm per side due to LCA shims to run -3.0 camber. My rear fenders are rolled and you will probably need to do so. Tires on the car with the silver wheels are NT01 245/40/18 and 305/35/18. If you track you car at all, the NT01s beat the R888 hands down plus you can swap then side to side. They are also quieter compared to the 8s.








If you are AWD, than you're pretty much stuck with a 235/40/18 and 315/30/18 as pictured below with the car on NT01s and also 18x9x12s. This is what I ran prior to my current set up. Still works well, just not as well since the 315 has a smaller contact patch and rolls over more due to the softer sidewall. I can run about 4psi less on the 305 compared to the 315..

 

Powder hound, do you have rubbing upfront with the 9" inch wheel?

Just caught your ninja edit. Understood. Changed the fron to 8.5 and will run the 40 offsets with GT2 tire sizes.

 

I'd keep the 9s vs. the 8.5s. That won't make any difference if you keep the offset the same. Basically the tire bead will be stretched 1/4" per side but the centerline of the tire won't change. No issue with a 9" on 235s. I have no rubbing on my set up but I do not have a stock suspension. I am on JRZs with lower GT3 control arms w/ shims, 996 Cup uprights, and adjustable thrust arm bushings to dial in the caster. I am also running full GT2 fender liners along with -3 camber. The fit is tight but there is no rubbing whatsoever lock to lock. I do have a 245/40 which is a bit taller than a 235/40 (which would give you more clearance obviously).

Honestly, If I were you I'd run a 45 offset in the front on a 9" wheel. The 45 will tuck the wheel in a touch more and reduce the run radius of the wheel giving you a bit more clearance. Works well and gives you the option to run wider tires if you later desire. The 9" wheel will stiffen the sidewall of the tire a bit over an 8.5. An 8.5 et40 however works fine if you are going to stay mostly stock.

As a point of reference, I recently sold a local guy a set of 18x9 et45 and 18x12 et45 wheels. These are on his totally stock 996TT with PSS10s and a street alignment. Tire are 235/40 and 315/30 Pzeros. Zero rubbing. Hope that helps..

 

where its at .
235 40
315 30

you will be absolutely fine. no rubbing whatsoever.

 

How would 245/40's on 18x9's and 315/30's on 18x12's work? I'm thinking about picking up a set of R888's in those sizes. They're still within tolerance for an AWD setup (25.7" front and 25.5" rear) and would provide a bit more contact patch in the front. But I don't see many people running this setup which leads me to believe there might be issues.

 

you can do that without any issues.in fact, it will fill the wheel better (assuming 9" wheel) it'll reduce understeer too

 

For an AWD set up it's always better to have an ever so slightly larger diameter front than rear as it helps the AWD system transfer power to the front. 245/40 and 315/30 is a popular track set up and works well. 90% of track guys run this size in NT01s which run 25.55 and 25.35 respectively for the reasons I've mentioned before. It's also one of the most popular track R compound set ups for 996GT3s..

 

Awesome, thanks for the help guys!

 

Yes, Thank you gentlemen!

I ordered 18x9x45 and 18x12x40 so I can run 235x40 and 315x30 R888's. I'll post pics when they arrive. Actually, I'll be posting a thread on my mild/moderate build.