Thanks in advance for anyone who helps. At the moment I have a 348 with standard wheels and tyres. I have a set of 360 wheels. 18inch X 7.5front, 10rear. I dont want to change the hight or gear roll ratio of the car, so what size profile do I need? Normal 360 Front 215/45 18 Rear 275/40 18 Normal 348: front 215/50 17 rear 255/50 17 360 wheels for a 348 having the same ride hight. FRONT: 215/?? 18 Rear: 275/?? 18 Need to know the ?? Thanks again.
348 normal size is 215/50/17 front and 255/45/17 rear. I have 18 in wheels and have 225/40 front and 265/40 rear. You can get 275/35/18 and they will work, but not always available. 215/?/18 are limited in tire manufactures. you might be better with 225/40/18 on the front. Check out www.tirerack.com and you can see specs for most manufactures.
Circumference 215/50 17 = 80 inches Circumference 215/45 18 = 80.48 inches Circumference 255/50 17 = 84.95 inches Circumference 275/40 18 = 83.76 inches There are many sites with calculators you can use. Here's one I found. http://www.csgnetwork.com/tireinfo4calc.html
You can estimate diameter from the tire and rim specs: 17" rim = 8.5" diameter * 25.4 mm/inch = 215.9mm radius. 215/50 :: 215mm tread width, *0.50 aspect = 107.5 sidewall height (approx) 215.9 radius + 107.5 height = 323.4 mm radius :: 646.8 mm (25.46") diameter. On the tire manufacturer's site, you'll find specifications for their tire types. The specs you're looking for (aside from load rating) is rim width range and diameter (or revs per mile -- based on circumference = pi*d). From Yokohama: es100: 215/50ZR17 measured on a 17x7" rim: overall width 8.8", overall diameter: 25.5", 815 revs/mile. So the estimate (25.46) was pretty close. Look up the revs/mile of your stock tires. Then find tires for the width and diameter of your rims, and look for the series (50,45,40) that are closest to the stock revs/mile. That way, your speedo (and odo) won't be too far off. Frankly, you may have trouble fitting those rims. 7.5" is a narrow rim for 18" dia. There aren't too many 215 width tires for 18" rims, either. That may have been a typo, but I don't think you want to go from 255 to 275 width on the rear without also going wider on the front. But you may have trouble getting a 255 width tire to fit on a 10" wide rim. If you can match diameter, you'll be okay on vertical clearance in the wheel wells, but if your new tires are a wider tread, look to see if you have horizontal room in the wells -- especially when you turn the front wheels. I don't know the width of the stock 358 rear rims, but going to an 18x10" rear rim might have trouble clearing the hub assemblies, too. Sometimes you need to add spacers to the hubs if the tires rub the insides of the wells. On ricers, they sometimes have to roll the fenders to make more room on the outside of the wells. And spacers tend to muck up the steering geometry, too. All that's the theory. Much of the practice is to ask people what sizes they've run on their cars. (Should "tires that worked on an xxx" be in a technical section somewhere?)
348 rears are 255/45/17 = 81.79 in. circ. or 26.04 in dia. That would be closer to 275/35/18 = 80.36 in circ or 25.58 in dia. or 265/40/18 = 82.77 circ or 26.35 dia.
You can fit 235- 40-18 on the front, but you might have to roll the front arches slightly. On the rear 295-35-18`s will fit ok.
DrT. is setting you straight. I had stock modena wheels & tires at first on my 348. Good thing the tires were wearing out, because they're too tall. For the swap, I chose PS2's , and moved down one aspect ratio from the stock modena tires - 275/35 & 225/40. (couldn't get 215's for the front) Compared with stock modena tires, it looks more natural with a little extra clearance between the tires & fenders. Ratio's are close to being exact with stock 348 diameter. More importantly, I haven't experienced any tire rub since the swap. Thanks Brotherhood.
