Tire sizes (max) on stock rims
 

I have a 2008 base which i've looked up stock rims are 18x8.0 front 18x8.5 rear and im looking to fill up the wheel well without rolling,or rubbing during turns. I also don't have TCS so no need to worry about that. Also it will just be for spirited driving, no tracking, drifting etc.

with these stock rims at stock height, no plans on coil overs anytime soon and don't plan on new rims anytime soon what is the cleanest sizes i can get away with?

It seems most people have answered with 245/40/18 front and 265/40/18 rear
but i've also seen some people bump the rear up to 275, and some do 245/245 but the middle tire number ranges from 35-45.

Which if i understand corrently the first number is width of the tire, second is the height of the sidewall, and the 3rd is just the size of your rim (18)?



So basically 245/40/18 - 265/40?/18 or 275/?/18

Sorry i am trash at wording things and thanks for the help :thumbup:

If you take a tire size, for example. 245/40/18, the 245 is the tire width in millimeters. The 40 represents the side wall as a percentage of the width. "40% of 245 mm". The 18 represents the diameter of the rim. There are limitations as to what size tire can fit on what size rim. Many people push those limitations. My friend has a Mustang GT with Mickey Thompson drag radials that are 285 width on 7.5 inch OEM width on his rear. The tire dramatically hangs outside of the rim, and in my opinion, looks silly. But it's a straight line drag strip car that allows him to get away with it. For our Z's, I would keep the tire as close to a proper fit, for hard cornering, which is what our cars are engineered for. On the OEM 18's on your car, 265 on the rear are as wide as I would go. Maybe you could get away with more but I wouldn't push it on an 8.5 inch wide rim. I have 275/35/19 on my rear on the Track V2 19x10, and they fit and handle perfect on stock suspension.

Attachment 453601

The bottom is a Nitto NT01 265/40/18 on the same stock 18x8.5 rims you have
The top is a Firestone Indy 500 275/35/19 on OEM 19x10 Track V2

There isn't much difference between the two as different tire manufacturers vary in tire fit and finish. The Nitto is a drag radial and the Firestone is a summer ultra high performance.
Hope this helps.

For optimal fit (not "will it mount on the wheel?"), use the 120% (or 1.2) Factor.... tire width shouldn't exceed 1.2x/120% of the wheel width. Sure, you can mount a 285 on an 8.5" wheel but that doesn't mean you should do it. 8.5 wheel shouldn't have a tire on it larger than 259mm (or a 255 or 265).

Likewise, one shouldn't go less than 90% (or 0.9x) under wheel width.

I'm running 275/35r18 on the stock 18x8 wheel in the rear. Would I do it again? Probably not. Causes the edges to not touch the ground(almost like the tire is over-inflated) Although, I don't think I'll ever drive enough miles to wear them out. As far as handling/accel I am not really sure. I put them on when I turbo'ed and never had a comparison.

At the track, I see guys airing down to 15 psi to get that full patch you're talking about, and from a dig, it makes a big difference.

I had to drop it to around 20 psi when I took my car to New England Dragway, but you can't drive like that otherwise

For your objective (“fill up the well”) and limited to OEM wheel specs (8.0” & 8.5”); consider (F) 235/45 and (R) 255/45**. Gives you a tad more diameter (height) along with some added foot-print (width) and maintains ratio (the nat's ass math). No free lunch though, comes with a little more side-wall as well. Also, less summer performance tire options in that sizing combination. Plenty of good choices if you are looking for all-season treads.

As mentioned above, while you “can” install a wider cross-section on those narrow rims that doesn’t mean you should. Again, performance trade-offs, and not always in your favor when you start going too far astray with sizing.

Your reference to 245, 265 and 275 in 40-series is the opposite of what you are trying to accomplish (shorter = less visual fill at stock height) and a 275 on an 8.5” is something I would avoid altogether. In the end, you’re probably better off rollin’ OEM tire specs on those stock wheels, 225/45 & 245/45 for a host of reasons.

Spend time running sizing on the following calculators, or use other tools readily available on the net, you’ll answer your own questions. Otherwise there's a "spoon" meme in your future :icon39:

** Actual measurements and fitment can and will vary to a degree regardless of what’s on the sidewall or what a calculator indicates (variables in the real-world).

https://tiresize.com/comparison/

http://www.tyresizecalculator.com/ty...ize-calculator

http://www.tyresizecalculator.com/ty...dth-calculator

OK trick for the drag strip. Please don't attempt this on a road course.

With your wheel sizes (8.0" and 8.5"), I would go with 245/40/18 front and 265/40/18 rear. You could certainly mount 275's on the rear (10 mm is a small difference).

This is combo I normally run on Touring V2 OEM wheels for DD and track duty. However I recently switched to 245/45/18 and 265/45/18 since that what RE-71Rs come in. This setup fills up wheel wheels nicely because the sidewalls are larger (since 45 > 40). Overall the tires are .75" (nearly a full inch) taller overall then stock, but only raise the car half that amount (.38") so its not huge but noticeable. Also technically this throws off the speed-o by 2 mph at 80 I think.

I have went ahead and ordered 245/40/18s for the front and 265/40/18s for the rear, when i bought the car they came with 225/40s all the way around.

Did you check your rear wheels to make sure they are indeed staggered and the previous owner didn't swap them out?

i got them put on at firestone, do they normally take your car out for a drive after installing tires?

The tire shop may not (probably will not) test-drive the car after installing new tires, but they may ask that you return after a day or two to test the torque on the wheel bolts.

Testing the torque on wheel bolts is a common practice for tire shops when installing 265 or greater width tires.

This is why I mount and balance my own tires.

OK... But does that not require having access to some specialized equipment?

I would say it's uncommon to have a tire mounter in a residential garage, but it's not really a specialized tool since it's universal for tires. I paid $400 for the machine and use balancing beads(for balancing).

Yea i called and they said they do not typically do that but since the car has tpms they were trying to clear the code, but i think the guy just wanted to go for a joy ride, i have a tomei on it and i heard it going down the road at easily 4000 rpms. You live and you learn i guess.