Can someone explain tire sizes?
09-14-2001, 05:24 AM
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Can someone explain tire sizes?
I'm confused on tire sizes. I hear terms like 245/55/16 and the like. Can someone explain what the numbers mean and how can I calculate them?
09-14-2001, 07:05 AM
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From TireRack.com:
The first number is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, divide by 25.4 In the example above, the width is 185mm or 7.28".
The second number is the aspect ratio. This is a ratio of sidewall height to width. In the example above, the tire is 7.28" wide, multiply that by the aspect ratio to find the height of one sidewall. In this case, 185x0.60=111mm or 7.28"x0.60=4.36".
The last number is the diameter of the wheel in inches.
The first number is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, divide by 25.4 In the example above, the width is 185mm or 7.28".
The second number is the aspect ratio. This is a ratio of sidewall height to width. In the example above, the tire is 7.28" wide, multiply that by the aspect ratio to find the height of one sidewall. In this case, 185x0.60=111mm or 7.28"x0.60=4.36".
The last number is the diameter of the wheel in inches.
09-14-2001, 07:17 AM
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Squeezer,
The sidewall markings are important to determine the size of the tire...but there are a couple more factors invovled.
1. Treadwidth
The first number 255/35/18, may tell you the width of the tire from sidewall to sidewall...but it won't tell you how wide the tread width is. For example...our stock S02's have a sidewall to sidewall rating of 225, but everyone knows that the tread width is wider than some 255/35/18's. Tread width is determined by the manufacturer and can sometimes be found on the manufacturer's site.
Tread width is important to know for performance evaluation and to estimate weather you will have any rubbing issues if your car is lowered and you have a set of aftermarket wheels.
2. Overall diameter
The overall diameter is important when trying to put different size tires on your car. Our stock tire diamter is 24.8 inches and when you are trying to use wider or smaller profile tires, it is good to stay close to the stock size. For example, 245/45/16 has around a 24.8 inch diameter, and so does 245/35/18.
The sidewall markings are important to determine the size of the tire...but there are a couple more factors invovled.
1. Treadwidth
The first number 255/35/18, may tell you the width of the tire from sidewall to sidewall...but it won't tell you how wide the tread width is. For example...our stock S02's have a sidewall to sidewall rating of 225, but everyone knows that the tread width is wider than some 255/35/18's. Tread width is determined by the manufacturer and can sometimes be found on the manufacturer's site.
Tread width is important to know for performance evaluation and to estimate weather you will have any rubbing issues if your car is lowered and you have a set of aftermarket wheels.
2. Overall diameter
The overall diameter is important when trying to put different size tires on your car. Our stock tire diamter is 24.8 inches and when you are trying to use wider or smaller profile tires, it is good to stay close to the stock size. For example, 245/45/16 has around a 24.8 inch diameter, and so does 245/35/18.
09-14-2001, 04:00 PM
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I don't know about you guys, but personally, I've always felt that tire sizes are about the stupidest sizing-standard i've ever encountered.
There are 3 dimensions in the tire specification: width, inside diameter, and aspect ratio (ultimately used to calculate outside diameter), and NONE of them uses the same measuring system !!
The width is in millimeters (metric)
The inside diameter is in inches (british)
The aspect ratio is a percentage (neither)
Furthermore, the tire width never really tells you either the tread width or the corresponding wheel width - these are things you have to inately know about different tire sizes.
Why couldn't they have just done something like:
8-2-16 - where
8 corresponds to the width in inches,
2 corresponds to the thickness of the tire, and
16 corresponds to the diameter of the wheel?
Then, at least you'd have an easier time fitting wheels and tires together !!
Just some food for thought.
There are 3 dimensions in the tire specification: width, inside diameter, and aspect ratio (ultimately used to calculate outside diameter), and NONE of them uses the same measuring system !!
The width is in millimeters (metric)
The inside diameter is in inches (british)
The aspect ratio is a percentage (neither)
Furthermore, the tire width never really tells you either the tread width or the corresponding wheel width - these are things you have to inately know about different tire sizes.
Why couldn't they have just done something like:
8-2-16 - where
8 corresponds to the width in inches,
2 corresponds to the thickness of the tire, and
16 corresponds to the diameter of the wheel?
Then, at least you'd have an easier time fitting wheels and tires together !!
Just some food for thought.
09-14-2001, 05:28 PM
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not a bad thought.. but I'd prefer it all to be in mm. with the 3 measurments being:
treadwidth
wheel diameter
overall diameter.
It'd make it much easier to determine how close of fit a particular tire is.
treadwidth
wheel diameter
overall diameter.
It'd make it much easier to determine how close of fit a particular tire is.
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