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Old 07-17-2012, 03:37 AM   #1
MR 325
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How Does Tire Sizing Work? READ THIS

  • Tire

    • Tires only have one shape, but they have many sizes. The size (along with other pertinent information) is stamped on the sidewall of the tire. It has three measurements of the tire and the numbers are separated by forward slashes. Use the following tire size as an example to break down the definition of the size of the tire. 185/65/R15. The numbers and letters after this number define the speed and load ratings of the tire.

  • Tire Width

    • The width of the example tire is 185 millimeters. This measurement is measured with the tire mounted and inflated to specifications from the widest point of the sidewall to the widest point of the opposite sidewall; straight across. The higher the number, the wider the tire. The lower the number, the narrower the tire.

  • Aspect Ratio

    • Also known as the section height of the tire, this measurement is used to determine in a percentage, and measures the sidewall from the wheel to the tread. In the case of the example tire, the aspect ratio or height of the tire is 65 percent of the section width of the tire. The higher the aspect ratio number, the taller the tire. The lower the number, the shorter the tire.

  • Diameter

    • The last number on the example tire size is the diameter of the tire. In this case, 15. The "R" before the number indicates it is radial ply. This is the most common letter you will see there for car tires. The number after the letter "R" is the measurement of the size of the hole in the middle of the tire, and determines what size rim or wheel to mount the tire on in inches. While some heavy duty trucks may use 1/2 inch size (like 16.5) most all cars only use inches. The example tire size has a diameter of 15 inches, and will only work on a 15 inch wheel.

  • Tire Size Conversions

    • There may be other sizes you can deviate from for your vehicle. Often, this information will be offered on the tire label. For example, if your car took the specific tire size used in the example size, it may also display another number at the bottom of the label in a 16 inch rim. The rim and tire for each wheel would have to be changed, but the information would provide you with another option that would fit the wheel well of the car without interfering with the suspension or chassis components of the car. Also, most reputable tire dealers will have a tire size conversion chart where the actual tire size of your car can be compared to similar sizes from which you may want to deviate. For example, you may wish to go with a wider tire or a taller sidewall tire. This size conversion chart would show in inches and/or millimeters how much difference there is between the actual size and the size you desire.
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Old 07-17-2012, 04:49 PM   #2
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I think my stupidity was just responsible for a sticky...
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Old 08-03-2012, 10:44 AM   #3
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Most people know about this, but...

Here's a handy tool you can use to see how much bigger or smaller a tire is going to be compared to stock and how that will affect your speedometer.

http://www.miata.net/garage/tirecalc.html
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Old 08-04-2012, 10:34 AM   #4
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these 2 are pretty cool sites too..

http://www.kouki.co.uk/utilities/vis...ize-calculator

http://www.1010tires.com/tiresizecal...r-snt-emty-str
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Old 08-04-2012, 11:12 AM   #5
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This is also useful:

http://customwheelsmarket.com/rimwheelwidth1.html
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Old 08-05-2012, 04:55 PM   #6
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Thanks guys!
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Old 11-14-2012, 08:38 PM   #7
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Quote:
Originally Posted by MR 325 View Post
  • Tire

    • Tires only have one shape, but they have many sizes. The size (along with other pertinent information) is stamped on the sidewall of the tire. It has three measurements of the tire and the numbers are separated by forward slashes. Use the following tire size as an example to break down the definition of the size of the tire. 185/65/R15. The numbers and letters after this number define the speed and load ratings of the tire.

  • Tire Width

    • The width of the example tire is 185 millimeters. This measurement is measured with the tire mounted and inflated to specifications from the widest point of the sidewall to the widest point of the opposite sidewall; straight across. The higher the number, the wider the tire. The lower the number, the narrower the tire.

  • Aspect Ratio

    • Also known as the section height of the tire, this measurement is used to determine in a percentage, and measures the sidewall from the wheel to the tread. In the case of the example tire, the aspect ratio or height of the tire is 65 percent of the section width of the tire. The higher the aspect ratio number, the taller the tire. The lower the number, the shorter the tire.

  • Diameter

    • The last number on the example tire size is the diameter of the tire. In this case, 15. The "R" before the number indicates it is radial ply. This is the most common letter you will see there for car tires. The number after the letter "R" is the measurement of the size of the hole in the middle of the tire, and determines what size rim or wheel to mount the tire on in inches. While some heavy duty trucks may use 1/2 inch size (like 16.5) most all cars only use inches. The example tire size has a diameter of 15 inches, and will only work on a 15 inch wheel.

  • Tire Size Conversions

    • There may be other sizes you can deviate from for your vehicle. Often, this information will be offered on the tire label. For example, if your car took the specific tire size used in the example size, it may also display another number at the bottom of the label in a 16 inch rim. The rim and tire for each wheel would have to be changed, but the information would provide you with another option that would fit the wheel well of the car without interfering with the suspension or chassis components of the car. Also, most reputable tire dealers will have a tire size conversion chart where the actual tire size of your car can be compared to similar sizes from which you may want to deviate. For example, you may wish to go with a wider tire or a taller sidewall tire. This size conversion chart would show in inches and/or millimeters how much difference there is between the actual size and the size you desire.
on the picture of you car, what wheels are those?
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Old 12-10-2012, 01:38 PM   #8
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I know I've seem multiple sites that have pictures of variously sized tires on variously sized wheels.

This is one of them:

http://tyrestretch.com/

What are some others? I know there are some out there...
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Old 12-10-2012, 01:48 PM   #9
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Also keep in mind for very close fitment issues that not all tires are the same. not every 225/50/16 is going to be the same. Some brands may run wider even though it may be a "225"
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Old 12-10-2012, 04:56 PM   #10
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Originally Posted by future rs View Post
Also keep in mind for very close fitment issues that not all tires are the same. not every 225/50/16 is going to be the same. Some brands may run wider even though it may be a "225"
That's right.

And under tire width, contact patch should also be noted.
"This measurement is measured with the tire mounted and inflated to specifications from the widest point of the sidewall to the widest point of the opposite sidewall"
That means two tires could have the same "225" width, but one could have a larger contact patch than the other, for several reasons, like it being a summer vs winter tire or the tire having a larger or smaller aspect ratio.
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Old 12-10-2012, 05:35 PM   #11
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What are some others? I know there are some out there...
Found it!

http://rimtuck.com/
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Old 12-10-2012, 06:01 PM   #12
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Also, with *most* R-comp or like R-comp tires... they run wider than your average street tire!
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Old 12-10-2012, 07:54 PM   #13
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http://www.willtheyfit.com/
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Old 12-10-2012, 09:07 PM   #14
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Best one I've found:


http://www.rimsntires.com/specs.jsp
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would be in depending on tip slant and tube size
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Old 12-10-2012, 09:36 PM   #15
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That's right.

And under tire width, contact patch should also be noted.
"This measurement is measured with the tire mounted and inflated to specifications from the widest point of the sidewall to the widest point of the opposite sidewall"
That means two tires could have the same "225" width, but one could have a larger contact patch than the other, for several reasons, like it being a summer vs winter tire or the tire having a larger or smaller aspect ratio.
Thanks that's what I was looking for. Contact patch.
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