im about to get a set of 18" x 8.5 rims with out tires.. i found a set of 4 tires for a great price.. 2 are 225/40/18 and 2 are 255/35/18.. i just wanted to make sure both sizes would fit on the rims properly and sit well on the car.. i would assume the 255's are for the rear?...and not sure but possibly will be adding a 1.5" drop too and with or without that drop just want to make sure i will have proper clearance with this set up. any suggestions would help.. thanks

 

should be able to fit them no problem...i got 18x9.5 with 245x40 18 on the front(withc i dont like,i need wider) and in the back i got 18x274x40 with no problems.....

 

What width tire fits on what width wheel is determined by the tire manufacturer. Go to Tire Rack and look up the specific tires you want to buy. There will be a table of sizes that tells you the acceptable wheel width for each tire size.

You also need to insure the tire is the correct diameter. Your car left the factory with either 235/55-15 tires (26.1") or 245/50-16 (25.7"). The 225/40-18 will fit correctly on a wheel that is (typical - each tire has its own specifications) 7.5 - 9.0" wide. But the diameter is too small at 25.1".

Same problem with a 255/35-18. It will fit on a wheel 8.5 - 10.0" wide, but its a 25.0" tire.... too small.

Too small a diameter and you lose ground clearance, the gap between the tire and the fender grows, and for the rear tires, the speedo get screwed up, requiring a PCM programming adjustment.

A 275/40-18 is actually a bit oversize at 26.7". Its like swapping in a slightly lower (numerical) rear axle ratio.

 

so for each tire company the ratings are different? i was just looking at ebay's tire and rim combos and seeing all the different size tires they were including with 18x 8.5 inch rims. and i usually seen those sizes. so you dont think the set up i wanted to buy would work then? even with lowering springs?

 

i went on tire rack and looked at the 18" tires.. they showed me many different tires that would fit 18" rims on my car. but doesnt show sizes of the tires such as what fits on what width of rim im going to have. what size tires would you recommend i get then? i dont want super fat tires. but not the lowest profile tire .. id like something in the middle and would like to lower the car 1.5" possibly down the road.

 

On Tire Rack, chose "tires by size". Put in the size you want, and it will give you a list of all the available tires in that size. For anyh tire you are interested in, click on "Specs" and it will give you a table that includes the recommended wheel width range for that tire.

Each manufacturer sets the acceptable wheel widths. Mostly, they are the same for the manufacturers for any given tire size, but they are not absolute values. Often you will find, for example that Dunlop tires have a wider range than other brands. I've seen different models of tires form the same manufacturer have different width ranges. It doesn't hurt to check.

You need to find a tire that is a close diameter match to the stock tires that came on your car. What size did it have on it when it left the factory?

 

im not sure what it had on it when it left the factory. but i bought it and it currently has the stock rims with 245/50/16 tires all around.. so with that said what is the size range i would be looking to get with a 18x8.5 rim?.. ***i jus checked the site now and it shows for the 225/40 size it has a overal diameter of 25.3 and the 255/35 size has a 25.2 overal range.. and you said factory with 245/50/16 size had a 25.7 then is .4 or .5 of a difference really that much to make it a big deal or?

 

245/40-18 is 25.7". Fits on a wheel 8.0-9.5" wide. "Measured" wheel is 8.5". That is the correct size.

You could also run a 255/40-18, but its at the limits with an 8.5" wheel. It may look a bit "bulgey".

While 0.4" or 0.5" undersize may not seem like much, the reduction is all in the sidewall. Its going to look like you stretched a rubber band on the wheel. Ride will be harsher, and exposure of the rim to pothole damage increases. Tires turn faster at any given speed, wearing them out faster. Speedo is up to 2.5% off unless corrected in the PCM.

Not sure why you are looking at a narrow tire like a 225. Why go narrower than the stock tire. You're looking at the equivalent of the tire width that came on the base V6 models. You can find out what tires your car had from the factory by looking at the tag on the end of the driver's door, or looking at the build tag for RPO "QLC" (Z-rated tires, 245/50-16).

But, do what you want.... its not going to be unsafe, maybe just a bit less cornering power and straight line traction. And if you like the skinny tire look, and the "rubber band" look, who am I to question it?

 

no im not going for that look at all.. just want to know what size is best recommended.. i seen some people with 18's and they had like real fat tires and i wasnt sure wat size they were but i just know i didnt want them.. if your suggesting i get 245/40-18 size then ill look for them..