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racer_d · 11-30-2007, 01:40 PM

Just to expand on tire reading basics:

225 40 18

225 = section width of the tire, in millimeters

40 = aspect ratio - the percentage of the section width that then defines the sidewall height. In this case, the side wall height is 40% of the tires width (225 x .40 = 90mm)

18 = rim diameter in inches

so.. a 225-40-18 is both narrower (225<245) and "shorter" ( 40% of 225 =90, 40% of 245 = 98) than a 245-40-18.

11-30-2007, 01:40 PM	#3
racer_d Registered User Join Date: Nov 2006 Location: Virginia Posts: 846	Just to expand on tire reading basics: 225 40 18 225 = section width of the tire, in millimeters 40 = aspect ratio - the percentage of the section width that then defines the sidewall height. In this case, the side wall height is 40% of the tires width (225 x .40 = 90mm) 18 = rim diameter in inches so.. a 225-40-18 is both narrower (225<245) and "shorter" ( 40% of 225 =90, 40% of 245 = 98) than a 245-40-18. __________________ 1976 914 2.0 2000 Boxster 2.7 (sold) 1978 911 SC (sold) 1970 914 w/2056 (sold)