Ford 6.7 owners
What gear ratio do you have? I just got a '16 end of the year sale. Got everything I wanted except the gear ratio. Slim pickens this time of year. I ended up with 330's. I wanted 410 or at leas...
Forum Discussion
transamz9 wrote:alexleblanc wrote:
275/70R18 has a diameter of 33.3"
275/65R20 has a diameter of 34.1"
in my case the 295/60R20's that I'm running have a diameter of 33.9" so its somewhere in the middle.
Don't want to change the subject but what tire are you running? I've been looking around at different tires for when I do need them and I think I might step up a size width wise but don't want to go much taller.
You can convert tire size to diameter if you understand what the numbers refer to:
The first number say 295 is the width of the tire in millimeters. The second number is the aspect ratio expressed as a percentage. So 60%. It is the distance from the top of the rim to the top of the thread divided by the tire width and multiplied by 100. The R refers to radial and the 20 is the rim diameter in inches.
So a 295/60 R 20 tire will be 60/100 x 295 = 177 mm rim edge to top of tire x 2 because you have rim edge to pavement as well. Divide that by by 25.4 to get inches. So a total of 13.94 inches of sidewall plus 20 iches of rim yields a tire diameter of 33.94 inches.
A narrower 275/65 R 20 works out to be a fairly similar diameter 65/100 x 275 x 2 /25.4 + 20 = 34.07 inches.
