poor college student

Ok, i used the search function to look for tire size, determine tire size, and so on, but i couldn't find out how you decifer the tire size code... like people say 255/number/number... what does each number mean?

thanks in advance

~Jeremy

UniqueTII

225 - width in mm
55 - aspect ratio = percent of the width that is the height
17 - rim size in inches

poor college student

what do you mean percent of the width that is the height? call me dumb, but i don't get it.... i get the 225 and the 17 but just a little fuzzy on the aspect ratio....

rx7gslse

I have 265/60/16 on my truck.
265mm wide, 60series (very tall sidewalls) 16" diameter

For racing my 7 I run 225/45/13
225mm wide, 45 series, (fairly small sidewall) 13" diameter


The best site to get a visual for all of this: http://www.miata.net/garage/tirecalc.html

neo_omega

The first number is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, divide by 25.4 In the example above, the width is 185mm or 7.28".

The second number is the aspect ratio. This is a ratio of sidewall height to width. In the example above, the tire is 7.28" wide, multiply that by the aspect ratio to find the height of one sidewall. In this case, 185x0.60=111mm or 7.28"x0.60=4.36".

The last number is the diameter of the wheel in inches.

To figure the outside diameter of a tire, take the sidewall height and multiply by 2,(remember that the diameter is made up of 2 sidewalls, the one above the wheel, and the one below the wheel) and add the diameter of the wheel to get your answer.

Example...185/60R14 85H or 185/60HR14

185mm x .60=111mm x 2=222mm + 355.6mm(14")= 577.6mm or 22.74"

neo_omega

this belongs to tire/wheels section