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Tire diameter formula with known metric tire size.
#1091288
10/09/11 03:31 PM
10/09/11 03:31 PM
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Joined: Sep 2003
Posts: 1,168 Vancouver, WA
MoparMarq
OP
super stock
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OP
super stock
Joined: Sep 2003
Posts: 1,168
Vancouver, WA
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Some have posted on tire size swaps while seeking a specific tire diameter. Here's the formula for tire diameter.
Tire size is, of course, listed as "SW/AR-RD", where SW is section width (the width of the tire), AR is aspect ratio (the height of the sidewall of the tire expressed as a percentage of width), and RD is the diameter of the rim the tire is designed to be mounted on. E.G., 235/45-16 is a 235 millimeter wide tire with a sidewall height 45% of the width, designed to be mounted on a 16 inch rim.
Overall tire diameter is as follows:
TD = (SW x AR x 2) / 25.4 + RD
The term in parentheses is the height of both sidewalls and dividing by 25.4 converts the units from millimeters into inches for addition to the rim diameter. E.G., (235 x .45 x 2)/25.4 + 16 gives an overall diameter of the above mentioned tire of 24.3 inches.
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Re: Tire diameter formula with known metric tire size.
[Re: deansrr]
#1091291
10/09/11 09:24 PM
10/09/11 09:24 PM
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Joined: May 2005
Posts: 4,742 Florida
BDW
master
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master
Joined: May 2005
Posts: 4,742
Florida
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Re: Tire diameter formula with known metric tire size.
[Re: RodStRace]
#1091292
10/09/11 09:24 PM
10/09/11 09:24 PM
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Joined: Jan 2003
Posts: 4,588 St. John's Newfoundland
440newport
master
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master
Joined: Jan 2003
Posts: 4,588
St. John's Newfoundland
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Quote:
That is nice and sorta helpful, but as anyone who has worked in a tire store can tell you, 2 different brands of tire the same size can be different heights.
And widths. I had a pair of 225/70 Good-years that looked about an inch wider than a 225/70 BFG.
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