What do you guys think of these SSRs

When it comes to optimum wheel width to tire cross section width, really the tire manufacturer's specs will tell you what is allowed and what is recommended. For performance-sake, I've always said that it is better for the wheel to be wider then the tire then the other way around...within the reasonable limits of both the tire, the wheel, and the car itself. Meaning, if you put a 235/40-18 tire on a 8" rim, that's all well and good, but an 8.5" rim would be slightly better if the wheel didn't weigh more. Why? Because the tire is shaped better for handling with a slightly wider wheel. Its a case of geometry, really. A good way to prove this is to look at Porsche or other high-end cars and their stock tire size compared with their wheel size.

At any rate, the most important thing is to pick a tire size that fits the car, the wheel, and the situation you intend to put the car in. For our car, it comes with 214/45-18's stock in MS3 form, and fits our 18x7 wheels. If you want to go wider, you also will end up taller unless you drop your sidewall profile down to 40, so that makes going to a 225/40 or 225/45 incorrect (though it still works, it is indeed going to throw off your speedometer.) But a 235/40 OR a 245-40 are much, much closer to stock height and it will work far better. The only problem then is you need a wider wheel then the stock 7"! So, to accommodate this, the search begins for 18x8 or even wider wheels, but our offset requirements are very specific at these sizes. As jp4130 proved, an 8.5" wheel is possible if you select the right offset CAREFULLY. Now with a wheel that wide (or down to 8"), you can easily run a 235/40-18 or possibly maybe a 245/40-18. Your next enemy is the fender edges, because you are now pushing the limit of the available space in the fender well. A 235/40-18 is about the limit it seems, but I suppose you could roll the rear fender lip a bit and get a 245/40-18 in there relatively easily.

Once again, jp great job. That took balls to try, and I commend you for it. The tolerances you've shown are amazingly tight, yet it works. Its going to be exciting to find out if you can 245/40-18's on that wheel or if that is just too much. It depends on the tire, too! I've noticed each brand of tire has a slightly different shape to its tread style, and the smallest of changes here could make or break it for you. IMO, the 235/40-18 gives you the best of all worlds, plus you stuck WEDSPORT wheels on your ride and that's worth points alone.

Fourthmeal, is there any rule of thumb for optimum rim/tire width ratio?
The factory 7.5/215 works out to 88% rim/tire ratio, 8.5/225 would be 96%. Is that too much rim? 8.0/225 comes out to 90%. I would expect that the tire design would come into play on this. Something with stiff, straight sidewalls would probably be better off with a wider rim whereas a more traditional radial with the rounded sides might be better off on a slightly smaller rim. At least that seems reasonable to me, but I could be out to lunch.
 
Check out tirerack.com, they have specs for all the tires they sell (or most of them at least).
Here's the specs for the stock tires on the MS3s.
The columns: Meas. Rim Width and Rim Width Range tell you what size wheels the tires will work with.

From what I've seen (from experts like fourthmeal) it's probably not a good idea to push the wheel/tire combo to the limits of the manufacturers' specs.
So, even though the stock 215/45 18s could probably be forced onto a 6.5" rim it's not wise.
 

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Thanks for the compliment of being an expert, but I'm just applying knowledge gained from doing this type of stuff for a while now. I wouldn't say I'm an expert since I'm no longer in the business...I'm just happy to help if I can because others have helped me and I know it comes back to me through Karma or whatnot.
 
Fourthmeal, if you did this for a living, you are now our official expert. Bask in the glory.
The stock rims are 7 inch? I don't know why the hell I thought they were 7.5.
It sounds like you agree with my theory that the widest recommended rim for the tire in question is the way to go.
Maybe I'll just stick with the factory tires on a wider rim and avoid the whole speedo calibration issue... naaaahhhh!
 
Yes. I was a tire/wheel specialist at NTB, Sears, and briefly at my own shop (that was a FAIL), so maybe 4-5 years of down and dirty install work and planning for people and their custom setups. One advantage I had was we could order truly custom wheels if needed, ones that had infinite offset choices and that was a plus when working on some rare breeds.

I sold:

American Racing
Prime
Centerline
TSW
Enkei
Pretty much anything available at TireRack
BBS
Motegi
a few other crazy brands like those out of Keystone catalogs and such.

My best wheel install experience:
An Integra Type R (original!) with 17x8 BBS RK wheels, with some nice wide rubber that fit like a glove.

My worst wheel install experience:
A Suburban on 22" wheels back when they weren't really super-popular, and the tires weren't really perfected. That b**** was impossible!
 
When it comes to optimum wheel width to tire cross section width, really the tire manufacturer's specs will tell you what is allowed and what is recommended. For performance-sake, I've always said that it is better for the wheel to be wider then the tire then the other way around...within the reasonable limits of both the tire, the wheel, and the car itself. Meaning, if you put a 235/40-18 tire on a 8" rim, that's all well and good, but an 8.5" rim would be slightly better if the wheel didn't weigh more. Why? Because the tire is shaped better for handling with a slightly wider wheel. Its a case of geometry, really. A good way to prove this is to look at Porsche or other high-end cars and their stock tire size compared with their wheel size.

At any rate, the most important thing is to pick a tire size that fits the car, the wheel, and the situation you intend to put the car in. For our car, it comes with 214/45-18's stock in MS3 form, and fits our 18x7 wheels. If you want to go wider, you also will end up taller unless you drop your sidewall profile down to 40, so that makes going to a 225/40 or 225/45 incorrect (though it still works, it is indeed going to throw off your speedometer.) But a 235/40 OR a 245-40 are much, much closer to stock height and it will work far better. The only problem then is you need a wider wheel then the stock 7"! So, to accommodate this, the search begins for 18x8 or even wider wheels, but our offset requirements are very specific at these sizes. As jp4130 proved, an 8.5" wheel is possible if you select the right offset CAREFULLY. Now with a wheel that wide (or down to 8"), you can easily run a 235/40-18 or possibly maybe a 245/40-18. Your next enemy is the fender edges, because you are now pushing the limit of the available space in the fender well. A 235/40-18 is about the limit it seems, but I suppose you could roll the rear fender lip a bit and get a 245/40-18 in there relatively easily.

Once again, jp great job. That took balls to try, and I commend you for it. The tolerances you've shown are amazingly tight, yet it works. Its going to be exciting to find out if you can 245/40-18's on that wheel or if that is just too much. It depends on the tire, too! I've noticed each brand of tire has a slightly different shape to its tread style, and the smallest of changes here could make or break it for you. IMO, the 235/40-18 gives you the best of all worlds, plus you stuck WEDSPORT wheels on your ride and that's worth points alone.

Thanks dude. Ya I should have really pushed my luck with 245s; Next set for sure. I was pretty nervous about going bigger than 235 with this offset.
I totally agree with you about the brand of tire having huge effect. 235 from one brand being just right, does not garentee that all 235s will be right. Thats ok though I plan on sticking with bs potenza re01rs. Judging by my 235s 245s of this tire should still have a nice crisp sidewall wheel relationship.

Those rx8 wheels look better on the speed3 than they do on the rx8.(headbang)

Oh ya, it's cool that at least one person agrees with my threorys. (drive2)
 
Very likely you'll find it by asking the RX8 guys, but if I recall it is pretty light. Most importantly, it is wide enough to fit a 235/40-18 no problem,...maybe a 245/40-18 if you're lucky (or if you don't mind rolling the rear fender!)


edit : Found on wheelweights.net that they weigh 22lbs. Or, about as much as ours do stock. Still, being an inch wider, you've gotta love it.
 
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