jumper5836

Will this combo work on our 996tt's?

235/40/18
305/35/18

PAULUNM

With that front tire, I would go with the 315/30/18 in the rear. OE GT2 sizes, front to rear ratio is acceptable for our AWD system.

I don't know how the height of the 305 compares to the 315.

philstireservice

Usually a 305 and a 315 are the same height ( or close) because of the aspect ratio

305/35R18
315/30R18

SelectiveRecall

What wheels are you using?

jumper5836

I am running OZ 18's 8" on front and 10" on back. I've run 235/40 front and 295/30 and 295/35 on back with no issues. 315's wont fit on the 10" rims and my car is lowered which even on stock wheels seems like they are too close to the outer wheel arch and could rub if you hit a bump to hard.

This is what it looks like with 295/30 on 35's look even closer

powdrhound

I used to run the common 235/40/18 and 315/30/18 NTO1 combo but I've been running the NTO1 245/40/18 and 305/35/18 combo since this size came out this past year. On my 3rd set already. The 305/35 runs very wide and I use 18x9 and 18x12 wheels. The tires sit very square on this wheel size. I wouldn't use anything narrower. Chris, who set up my car had me switch to the 305/35 and I love it. Awesome set up compared to the 315/30/18 I ran before. The 305/35/18 is over an inch taller than the 315, 26.42" v. 25.3", and also carries a higher load rating. There is a lot less rollover on the 305/35 and I can run about 4lbs less pressure with it. Grip is also better as you get a larger contact patch with the taller 305 and it gives the car some rake. Really a win win all the way around. The only caveat is the fact that you have to be RWD to run it since it's so much taller than the front.

http://www.flickr.com/photos/87731073@N06/10161515464/
http://www.flickr.com/photos/87731073@N06/11977202846/

996TWINS

If you like to stick with the OZ's, use the GT2 12" (no spacer) or the GT3 11" (with a spacer , IIRC 14mm).

Odd the OZ makes a 10" rim when the OEM size comes with an 11".

I use the OZ 11" so I can use 295, 305 or 315 tires.

powdrhound

The 10" wheel is a Boxter/Cayman size wheel....

996TWINS

Agreed. When you search Tire Rack for an 18" rear for a 996 Turbo it gives you a 10" (?) and 12" rear wheel option.

jumper5836

10"'s can run 265-305. So no problem there, winter tires are 265's. 10's are lighter as well.

I am more concerned about the height of the tire. Are 305/35/18 taller then 295/35/18. I can run those but they are a very tight fit with only a pinky between the fender lip and side wall.

powdrhound

A 305/35/18 will be taller than a 295/35/18. Look up the manufacturer specs. 30 seconds with google will give you your answer. Even though within spec, NT01 305/35/18 will be super pinched on a 10" wheel. It sits square on a 12" wheel. Handling will also suffer on a 10 vs 12 as the tire will roll over much more on the skinny wheel.