Guys,

Thought this may help everyone who is contemplating replacing their tires or wheels or both. I used this to calculate the actual tire diameter of my OEM 255/70x16 Goodyear tires at 30.06"

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"Performance Formulas:

You can calculate nominal dimensions by using the following calculation. Individual tires may vary slightly from these dimensions.

Using tire size of 235/60 R H 15 as an example.

TO CONVERT TIRE SECTION WIDTH IN MILLIMETERS TO INCHES:

Section width in millimeters ÷ 25.4 (standard metric conversion formula) = Section width in inches

EXAMPLE:

235 ÷ 25.4
= 9.25" nominal section width

TO CALCULATE TIRE SECTION HEIGHT:

Section width x aspect ratio percentage=section height

EXAMPLE:

9.25 x 60% = 5.55" nominal section height


TO CALCULATE NOMINAL OVERALL TIRE DIAMETER:

(section height x 2) + wheel diameter = overall tire diameter

EXAMPLE:

(5.55 x 2) + 15 = 26.1" nominal overall diameter"

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Borrowed from this web site which incidentally has other excellent technical tire information.

http://www.tyres1.com/tech.html

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Dunbarton "The Middle Aged Kid" '99 XLT SC SB 4x2 4.6 auto 3.55 ls The occasional Z-71 Eater! Wedgewood & Denim, SuperChipped, Airaid FIPK, HD electrical and cooling, power seat, Rhino Liner, Extang Classic tonneau cover, Mobil 1. Man, I got it all! (New Jersey)