tires math formula
 

Whats the correct formula for converting P metric tire size to diameter in inches ?

Im trying to figure out what P metric size 15" tires are around 31" tall, but are 60, 55, or 50 series.
I want a couple 15" street tires somewhere around 8 or 9 inches wide and about 30 inches tall.
maybe 295/60/15 ? Or am I way off ?

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-'77 Electra 403/TH350
-'76 GMC C-1500 Sierra Classic 350 4-bolt/TH350, 3.40 ratio
-'68 C-10 chassis
-'72 K-5 chassis


http://communities.msn.com/RandyR72K5
Randy
Lincoln, IL
Flying wrenches are cool only when you are the person throwing them....
r72k5@hotmail.com

check with the manufacturer, bfg gives a ton of specs on their site www.bfgoodrichtires.com

Fast -

Tire size is a little wierd. The 50-60-70-75 numbers in the tire size are aspect ratios, or what percentage of the tire width the sidewall height is. On a tire sized as 255/70R15 255 would be the width of the tire in millimeters, 70 would mean the sidewall height is 70% of the tire width and r15 is the size of the rim the tire is to be mounted on. To convert millimeters to inches, divide the number by 25.4 - 255/25.4= 10 inches. 10 inches * 70%= 7 inch sidewall height. 7 inch sidewall height * 2 = 14 inches + 15 inch rim diameter = 29 inches of tire height.

Another example..

Ex: 225/45/17 your tire

225(width)X 45%(profile)= 101.25 x 2 = 202.50 / 25.40 (for metric conversion) = 7.97" + the 17"(rim size) = 24.97" for total size

So basically substitute the letters in bold with your new tire sizes, hope this helps

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Toms River NJ
(Transplanted Hoosier)

71 custom 20 - 307 3onthetree-bone stock *sold*
56 working Street rod (under construction)
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The number one cause of computer problems is computer solutions.

Neat! Thanks

------------------
-'77 Electra 403/TH350
-'76 GMC C-1500 Sierra Classic 350 4-bolt/TH350, 3.40 ratio
-'68 C-10 chassis
-'72 K-5 chassis


http://communities.msn.com/RandyR72K5
Randy
Lincoln, IL
Flying wrenches are cool only when you are the person throwing them....
r72k5@hotmail.com

theres also another formula. give me a while to find my four wheeler book that has it and i will tell you