I've posted this many times. This is the results of my tire size research:
European sized metric tires, such as a 185SR14 for example, do not have an 80% aspect ratio, but 82% or 83% (I forget which, but I think it's 82%). This changes things just a bit. I've added the Euro spec tires to the list of acceptable 14" and 15" sizes for buses.
Bentley says that the 3/4 ton (small nut) models came with a 6.40-15 tire, having a diameter of 27.16", +/- .24".
This makes the nearest European radial tire size a 185R15, and the nearest P-Metric size a 205/75-15.
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 185/82-15 6.0in 13.5in 26.9in 84.6in 748 -0.6% 195/80-15 6.1in 13.6in 27.3in 85.7in 739 +0.7% 205/75-15 6.1in 13.6in 27.1in 85.2in 744 0.0% 225/70-15 6.2in 13.7in 27.4in 86.1in 736 +1.1% 255/60-15 6.0in 13.5in 27.0in 85.0in 746 -0.2%
How about running 14" wheels on a 3/4 ton (small nut) bus?
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 205/75-15 6.1in 13.6in 27.1in 85.2in 744 0.0% 205/82-14 6.6in 13.6in 27.2in 85.6in 740 +0.5% 225/75-14 6.6in 13.6in 27.3in 85.7in 739 +0.7% 235/70-14 6.5in 13.5in 27.0in 84.7in 748 -0.6% 275/60-14 6.5in 13.5in 27.0in 84.8in 747 -0.4%
Good luck getting most of these on the back. I've gotten some big tires on the back of an old bus by letting the air out while wedging the tire between the drum and the body lip, and then refilling it after getting the wheel bolted up.
One ton (big nut) models came with 7.00-14 tires, having a diameter of 26.22", +/- .24".
This makes the nearest radial tire size a 195R14, and the nearest commonly available P-Metric a 205/75-14.
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 185/82-14 6.0in 13.0in 25.9in 81.5in 777 -1.3% 195/80-14 6.1in 13.1in 26.3in 82.6in 767 0.0% 205/75-14 6.1in 13.1in 26.1in 82.0in 773 -0.7% 225/70-14 6.2in 13.2in 26.4in 82.9in 764 +0.4% 255/60-14 6.0in 13.0in 26.0in 81.8in 774 -0.9%
How about running 15" wheels on a one ton (big nut) bus?
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 195/80-14 6.1in 13.1in 26.3in 82.6in 767 0.0% 175/82-15 5.6in 13.1in 26.3in 82.6in 767 +0.1% 185/75-15 5.5in 13.0in 25.9in 81.4in 778 -1.4% 195/75-15 5.8in 13.3in 26.5in 83.3in 761 +0.9% 205/70-15 5.6in 13.1in 26.3in 82.6in 767 +0.1% 235/60-15 5.6in 13.1in 26.1in 82.0in 773 -0.7%
If you're thinking of using a tire size not listed here, try the tire size calculator at http://www.miata.net/garage/tirecalc.html to see how it compares.
