Redleg

Hey...new to the forum, tried the search function and sifting through about 30 pages of posts but couldn't find the exact answer to the question. Any help is appreciated...

I'll be picking up my 2007 Mustang GT with the optional 17" bright cast aluminum wheels soon. My question is...what is the widest tire I can run on this rim? As I understand it...not all 17" rims are created equal. Is this a 17x8? 17x8.5? I've searched the Ford site and couldn't find the reference...can anybody clue me in/show me where they got this type of data?

I'm also concerned about height of the tire. The stock tires are 235/55. From what I understand...the tire is 235mm wide from sidewall to sidewall. The .55 aspect ratio means that the tire is 129.25mm "tall" from edge of rim to tread of tire. Am I doing this math right?

Assuming it's correct...

If I wanted to go to a 275/40/R17 tire...that would make the tire 275mm wide and 110mm tall (using the same math from above)....in other words...the tire on 275/40 tire on the rim would not sit as tall as the stock tire?

Same concept goes for a 285/50/R17 tire....285mm wide and 114mm tall...again not as tall...just wider.

Now going back to the top...can the stock 17" rim take that wide a tire? What's the process to find out? There are plenty of 275/40/R17 or 285/40/R18 tires available on Tirerack...I just don't want to asume that they'll fit on the stock tire.

Looking into the future...my tire selection is going to be important for when I lower my Mustang with either the Steeda or FR Handling Pack. I don't want to have too big a tire that can't accomodate the setup.

Any help is appreciated. Thanks.

Andys06GT

im looking at the exact same dilema.... here's what ive found so far. the 275/40R17 has infinite tire options. and you only and inch in height, but GAIN an inch in width. definately nice. havent coinfirmed if you can run that on the stock 17x8 bullets. yes, they're 8, not 8.5 but people have claimed runnin a 10.2" wide tire on them. ive done it on my f150, but for some reason it doesnt sit right with a car that ill be takin 115 mph at the track. gotta double check. another thing to look at, is the effect it will have on your gear ratio. if you begin with the 3.55 and have a 235/55r17 tire, then swap for the 275/40r17, it creates a 3.76 (plus or minus) gear ratio to the car, without actually swapping the gears. the drop in tire height means with the 3.55 gears, its still spins the RIM at the same speed, but the outter circ. is less, so the tire is moving faster. ask someone better in physics. im a layman. but yeah, i can enter numbers into a set equation and find the answer. someone will have to explain how you can have a taller tire, with different sidewall % and have the same diam. it makes purchasin a tire so hard. not to mention the stock wheel / tire size is an oddball to begin with. should just get some 16's....

97targa

You can't put a 275/40/17 tire on an 8" wide rim. It won't wear properly. The max is a 255/40. A 275/40 is made for atleast 8.5 more preferably a 9" wheel. I had 245/45/17 on my stock 17X8 Cobra wheels. It looked nice and very normal. I don't think you need to go wider anyway. Buy a set of 1" billet aluminum spacers off ebay for the rear and your car will have that wide stance look. They will fit with no clearance issue's. I had them on my GT and loved'em. I called them cheater plates...lol It makes your GT look like a GT and not a V6. You can pick them up for about $65 shipped. I bought mine off of EZAccessory on ebay. You can pull up community at the top of the page and type in their name and it will bring up their auction listings. They shipped out same day and I had a problem and they fixed it immediately. I would check them out!

Redleg

Thanks for the feedback. I'll check it out. Definitely after the wide stance. What's the deal with the gear ratio becoming 3.76? Because the tire is smaller (height), will I have quicker time off the line but less max speed? I have no issue with that since I'm not out to do 140 mph in my Mustang yet anyways.