Tire Size Question

[thekid54]

I'm looking for the overall diameter of a 215/75/15 tire. I know there are various tire size calculators on the net, but they don't seem to be totally accurate. For example, I have a set of 205/75/15's that measure 26-5/8", but all the tire calculators say they should be 27.1". Anyone have an actual measurement for a 215/75/15 tire?

[tonythezeek]

i'm not a tire guy but i think the discrepancy is due to the weight (of the vehicle). i can only guess that the calculators on the web only give you the number of a tire's diameter with no load. i've also noticed that some tire brands just bow a bit more than others.

[thekid54]

That very well could be, but the only load on my tire was just the weight of the rear axle.

[oldspowered67C10]

Looks like most manufacturers are advertising the overall diameters at around 27.7" for their truck 215/75-15. Go to tirerack.com, they show the specs on pretty much all of their tires

[7071Bluck]

You have to take into account the rim width too, if you put it on a 6 or 8 inch wide wheel it will be taller than say if you put on a 10 or 12 inch wheel

[SCOTI]

215/75/15 = section width/sidewall percentage/wheel diameter

215 / 25.4 = 8.464" (basic metric conversion of millimeters to inches)
8.464" x 75% = 6.348" (sidewall height is a percentage of the sectional width)
6.348" x 2 = 12.69" (sidewall height- top & bottom)
12.69 + 15" = 27.69" (combined sidewall height plus rim diameter)

So it's 27.69" approx as each manufacturer has some fudge to their numbers as well.