I'm still trying to decide the tire size that I want to run on my RX8 wheels(STILL at the pcoater's). Presently, I have the mazdaspped3 rear bar and am pretty happy with the handling on my 5 as it is. That said, I have no plans to lower it since Eibach makes no springs for the 5 in the US. Has anyone run a 235 40 on this wheel or another 18 x 8 wheel without rubbing? I wasn't sure if this should go under tire or wheel but since the tire thread mostly dealt with stock and larger sized 17's, I thought that this might be the place.
optional sizes other than 225 40 18 on RX8 wheel for the 5l.
- Thread starter hibern8r
- Start date
rodslinger
Member
At stock ride height I was running a 225-45R18 on MS3 wheels and rarely rubbed. I would have to be fully loaded with people and luggage then hit a big dip in the road for the rear to scrape. If you are going to leave it at stock ride height I think you could get away with a 235-40R18 with minimal issues.
phunky.buddha
Booga Booga?
- :
- DFW TX
- :
- No mo MZ5 want MX5
I run 235/45-17 without rubbing on +55 offset wheels, and I have enough room for 5mm spacers in the front without rubbing, also in the rear after I bent the humongous lips in a bit with a fender roller. Those rear fender lips are 17mm wide- WAY bigger than they need to be- and they're what cause the clearance issues in the rear. Your RX-8 wheels are +50mm offset, so you're essentially the equivalent to my +55 offset wheels with the 5mm spacers. I would run 235/40-18 or 245/40-18 tires myself, but if you're not willing to roll the rear fender lips a bit, you'll probably run into problems.
For reference, my tires are the Sumitomo HTR A/S P01, 235/45 on 17x7 wheels. The wheels are 1 inch narrower than the spec measured wheel (17x8), so my section width is right at about 9.0 inches instead of the spec 9.4- so that that into account when you're looking at specific tires. The general rule is that you lose about 0.2 inches of section width per half inch of wheel width that's below the spec measured wheel, and I've found that to be pretty consistent (same works with wider than spec).
My tire spec info:
http://www.tirerack.com/tires/tires...ehicleSearch=false&fromCompare1=yes&tab=Specs
You'll probably have no problems clearing the fenders with 225/40 or 225/45 tires since they usually come in right at the 9.0 inch width on an 18x8 wheel, but it'll be pretty close in the back. Oh, forgot that I was lowered- but my rear camber is still sitting very close to the factory setup. I'm probably about half a degree more positive than the factory setup, so if you stay at stock height and don't have to push the tops of the tires further towards the edges like I did, you'll probably clear 235/40 just fine. If you want to test things out, load up enough weight in your car to push the tires up into the wheel well, then measure the distance from the sidewall to the fender- take into account your stock tire specs and your wheel specs, then compare to whatever tire you want mounted on that 18x8 +50 wheel.
For reference, my tires are the Sumitomo HTR A/S P01, 235/45 on 17x7 wheels. The wheels are 1 inch narrower than the spec measured wheel (17x8), so my section width is right at about 9.0 inches instead of the spec 9.4- so that that into account when you're looking at specific tires. The general rule is that you lose about 0.2 inches of section width per half inch of wheel width that's below the spec measured wheel, and I've found that to be pretty consistent (same works with wider than spec).
My tire spec info:
http://www.tirerack.com/tires/tires...ehicleSearch=false&fromCompare1=yes&tab=Specs
You'll probably have no problems clearing the fenders with 225/40 or 225/45 tires since they usually come in right at the 9.0 inch width on an 18x8 wheel, but it'll be pretty close in the back. Oh, forgot that I was lowered- but my rear camber is still sitting very close to the factory setup. I'm probably about half a degree more positive than the factory setup, so if you stay at stock height and don't have to push the tops of the tires further towards the edges like I did, you'll probably clear 235/40 just fine. If you want to test things out, load up enough weight in your car to push the tires up into the wheel well, then measure the distance from the sidewall to the fender- take into account your stock tire specs and your wheel specs, then compare to whatever tire you want mounted on that 18x8 +50 wheel.
Ok, I appreciate the responses from you guys, but I need something more concrete. It hit me like 5 minutes ago that I have an extra RX8 wheel in the garage (its pretty crappy, that's why I never sent it to the p coater). Anyway, I'll go and get a used 235/40 tire on it and then do my own little experiments with loading and turning the wheel. If it doesn't work, at least I know to get the 225s, and if it does work, I'll have a full size spare!!!
phunky.buddha
Booga Booga?
- :
- DFW TX
- :
- No mo MZ5 want MX5
I gave you pretty concrete information... if you want more, you'll have to do your own fit checks like I did- which were very similar to what you're describing with your extra wheel. Don't expect the forum to do all your work for you.
My tirade about specs was just that- you'll have to look up the specifications for the specific tire model that you're putting on your wheel, then see how the section width checks out vs spec size for the wheel width that you're using. Mine came out right at manufacturer spec or a hair less (like 1/16" less), and then the 0.2" adjustment for every half inch of wheel width away from spec was dead on too. The only thing your used 235/40 is going to tell you for sure is that the exact same tire model again will won't clear- not all tires with the same size stamped on the sidewall have the exact same dimensions- they're all a little different. THAT'S why I'm telling you to go look things up.
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- 2008 Mazda5 GT
I think Phunky meant the folks have provided enough empirical evidence to answer your question. Any further and you’d need to do your own test fit, which you are going to do anyway so you both are on the same track. Don’t miss read each other’s tone.
Btw, Phunk brought up a good point. The side walls for every manufacturer ‘s tire will be slightly different so one tire just “might” pose a slight issue if you are pushing for max width. If you read up their spec sheets, some sell them with a “rim protector” design (more bulge).
May I suggest doing the spare tire backwards. SHOULD the 235/40/18 not fit, you are screwed. Whereas if you start with a 225/40/18 or 225/45/18 spare, which should fit, at least you KNOW it can be used as a spare. You then get see how much space if left and gauge if there’s enough space for 235/40/18. Do you plan to roll your fenders??
Btw, Phunk brought up a good point. The side walls for every manufacturer ‘s tire will be slightly different so one tire just “might” pose a slight issue if you are pushing for max width. If you read up their spec sheets, some sell them with a “rim protector” design (more bulge).
May I suggest doing the spare tire backwards. SHOULD the 235/40/18 not fit, you are screwed. Whereas if you start with a 225/40/18 or 225/45/18 spare, which should fit, at least you KNOW it can be used as a spare. You then get see how much space if left and gauge if there’s enough space for 235/40/18. Do you plan to roll your fenders??
