Help with tire sizes

Go to this link for the offset and tire size calculator to help you get the proper size wheel and tire.
Remember that the outside diameter of your new tire must be within 1% of your OE size.

Do you have staggered sizes now?
What size tires do you have now?
AWD?
Are you comfortable with wearing out tires quickly since they can't be rotated?
Are you OK with the additional cost of good quality rubber for the large, wide wheels - the larger size could cost anywhere from $50 to $200 more per tire depending on the tire you pick.
Are you OK with a significantly harsher ride of the much larger wheels (and the smaller sidewall)?
Are your roads good enough for a 19" wheel?
Why do you want the 19", very wide wheels?
These are questions you need to ask yourself. There are no wrong answers and it is OK to say "for looks" on the last question.
A quick tire size primer
19 (or 17 or 18 or whatever) is the size of the wheel diameter measured in inches from bead to bead (where the tire sits - so the actual diameter is always a hair more, but close). For modern passenger cars the sizes are always in whole inches.
The 285 (275, 255, 165 or whatever) is the width of the tire contact patch in mm - so a a 285 tire would measure roughly 285mm.
The 35 (40, 45, 50 or whatever - generally between 30 to 85 for passenger car tires) is the height of the sidewall expressed as a percentage of the width of the contact patch.
The standard size tire for a 350 is 245/45-17 . This means that the contact patch is about 245mm, the sidewall is 45% of that and it fits on a 17 inch wheel.
This means that the OE tire has an outside diameter of about 25.68 inches. Subtract the size of the wheel (17) and you are left with 8.68 inches. Divide that by 2 (because the "half" of the sidewall is on either side of the wheel and you come up with 4.34 inches - which is about 110.236mm. 45% of 245 is 110.2
To get the same outside diameter for a 19" wheel and a 285mm wide tire, you would need a 30 aspect ratio tire - a 285/30-19. That gives you a an outside diameter of 25.73 or about as close as you can get.
Let's look at the sidewall though. You've gone from a 4.34 inch sidewall to a sidewall that is 3.465 - or about an inch less.
Last edited by CEB; Jun 11, 2013 at 10:34 AM.

Do you have staggered sizes now?
-Yes
What size tires do you have now?
-18 OEM AMG wheels
AWD?
-No, RWD
Are you comfortable with wearing out tires quickly since they can't be rotated?
-Yes
Are you OK with the additional cost of good quality rubber for the large, wide wheels - the larger size could cost anywhere from $50 to $200 more per tire depending on the tire you pick.
-I am fine with better quality. Actually prefer it
Are you OK with a significantly harsher ride of the much larger wheels (and the smaller sidewall)?
-I think I will be fine with the harsher ride. I am wondering will there be a big difference going from 18 to 19?
Are your roads good enough for a 19" wheel?
- I believe so. I live in Irvine, So cal and i rarely see potholes here
Why do you want the 19", very wide wheels?
- This is mainly for looks. Also right now I have the continental pros that came with the car and they are becoming so loud whenever I drive. I know that 19s will give the car a harsher ride, but if I get a better quality tire would that reduce the noise?? I also want the tires to be flush with the side of the car and not sticking out.
The local shop recommended the michelin supersport, but I am not sure if I even need that type of tire. It seems a little overkill for my needs. I normally just commute everyday.
I was looking at the Michelin MXV4 Primacy. Ultimately, I want it for the looks but I want to also be on the safe side. I don't want to be having any issues with clearance or rubbing. Would the 285 be way overkill in terms of width? Also with the sidewall of 3.465, would that be an issue?
Thanks for the help again!
Last edited by alanme123; Jun 11, 2013 at 02:51 PM.
As far as tires are concerned, you need to decide about your driving style. Will you ever drive at temps going below 40 degrees (or about 50 degrees regularly) with this car? If so, then you'll need an all-season tire. In your neck of the woods you can probably get away with a performance all season tire.
I'm actually a fan of Conti. They have a very nice DWS tire that is reasonably priced.
As far as fitting flush with the wheel well, you'll take "offset" into consideration.
Somebody else is going to have to jump in here with thoughts of rubbing with 285's

Thanks for the help again...I heard good things about dws as well. I will look into that too
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