Biggest tire that wil fit a stock 18" RX-8 wheel?

I have been led to believe that a 245/40 r18 will fit the car on it's stock wheels. Local tire shops have said they will not fit. I have seen on other fora that 275/35 r19 fit all corners. Will the 245/40 r18 tires fit? All advice is appreciated.

Yes, those should fit on the stock wheel. I haven't done it, but I've seen other people use them.

I ran a 255/40/18 on OEM 18x8 350z wheels with no issue. The 245 will be fine.

I agree that 245 is possible, but it depends a little on the tire construction. Some tires are designed to fit narrower rims than their treadwidth indicates.

Ex: I can fit 275's on the OE RX8 wheels, but only because they're Hoosier A6's and designed specifically to get the widest contact patch on a narrow (stock) wheel.

I run 245/35 19's on the R3. 245/45 18 should be the same diameter and width. I have no problems.

245 is entirely possible, I've seen it several times.

I'm currently running 245/40/18 on my RX-8 with zero issues. Each tire manufacturer has a range of rim sizes their tires will fit. Check out the "spec" information on tirerack's website.

A few issues ago GRM ran an article which suggested maximum performance would be achieved by ensuring the rim is wider relative to the tire the tire. Based on this information my next set will be the stock 225/45/18.

245 would be great on a RX8. I had 255/40/18 (iirc) on my 350z and enjoyed it. The RX8 is a good deal lighter so I can imagine 245 would feel similar.

Thanks for the help. I have ordered BFG KDWs in the 245/40 size.

Snrub wrote: A few issues ago GRM ran an article which suggested maximum performance would be achieved by ensuring the rim is wider relative to the tire the tire. Based on this information my next set will be the stock 225/45/18.

Hold on, you're going to reduce tread width to get a slight tire stretch for better performance? Are you sure you're not putting the cart before the horse here? I'd think getting a wider rim to slightly stretch the existing tire would improve performance (but at the cost of the practical downsides to stretching tires...easier curb rash & de-beading, bead contamination)

Sorry I phrased that rather poorly. Let me look for the article I'm referring to and then I will clarify. :)

As all others have said yes there will be no issues, I run S1 own wheels with 235/40/18 kumho xs on an S2 with no issues at all (235/40 was a good bit cheaper then 245s) where did you get your tires from?

I have 245/40/18s on a set of rx8 wheels and they fit fine.

I think I'm running 245/35R18s on mine. Definitely 245 tread width.

In reply to JtspellS:

Tire Rack

I have 'kook R-S3 in 245/40R18 on OEM RX8 rims. Works great!

I know people that run staggered on their RX8 but they use aftermarket rims and the back are wider than OEM.

I forgot to do my follow up. In the December 2013 issue, page 126 there are lap time results for different tires on a road course.

Average/Best Laps

BFG Rival 8" rim - 205/50/15 - 84.03/83.65

BFG Rival 8" rim - 225/45/15 - 83.93/83.65

BFG Rival 9" rim - 225/45/15 - 83.47/83.18

Note that the 205 and 225 on the 8" rim have essentially the same performance. Going to a wider rim was needed to allow the 225 to improve upon the 205 results. This implies to me that you don't want to put the widest tire possible on a given rim width (eg. 245/40/18 on a 8" rim). You're better with the tire to rim ratio being a bit lower eg. 225/45/18 might be faster.

I can tell you that 245/40 18's will fit on the RX8 stock rims. I have bridgestone re760 sports on my RX8 and they are fantastic. They fit super "square" to the rim, meaning that the tires fit right over the very edge of the rim but they do fit with no rubbing.