Calculating tire sizes
Since this formula has been put in numerous posts but questions still pop up from time to time I thought I would throw the formula here.
Ex. tire size. 275/40/17 Breakdown 275 = width in millimeters 40 = aspect ratio of width (40%) 17 = wheel diameter Note.. 1 inch equals 25.4 millimeters Obviously to determine width in inches you would just divide 275 by 25.4 275/25.4= 10.83 inches To determine overall diameter of wheel/tire combo.. 40% of 275mm = X 275mm x .4 = 110mm Note that 110mm is only one sidewall and must be multiplied times 2 since you have 2 sidewalls when looking at the overall diameter of a wheel/tire. 110mm x 2 = 220mm At this point I convert the sidewalls to inches 220mm / 25.4 = 8.66 inches Add your wheel size (17" in this example) to 8.66 inches 17 + 8.66 = 25.66 So a 275/40/17 is 10.83 inches wide and 25.66 inches tall. Disclaimer. This is how formula is suppose to work. Actual size varies by manufacturers. For example Nitto drag radials will be a little narrower and shorter while there 555 street tire will almost be dead on with this formula. Also BFG KDW's seem to follow this as well. I don't know baout other tire brands. |
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