Tires: trailer tire size conversion, tire size conversion, st205 75r15

Question
Can metric size tires be safely run on rims that originally held 7.00-15, 8-ply tires?  I find conversion charts on the Internet, but cannot find any conversion for 7.00-15.  One discussion thread suggests that ST225/75 R15 load range D might work, but opinions in that thread vary.

Answer
Dick,

Sort of.

When radials were first introduced, there were a number of complaints about rims cracking.  I'm not 100% sure this was due to the radial construction in the tire, but it was certainly plausible.  But I think it is something that should be watched.

The load carrying capacity of a 7.00-15 8 ply rating is 1710# @ 50 psi single and 1520# @ 50 psi dual.  You should check the sidewall of the tire to be sure this is correct.

If so, then an ST205/75R15 Load Range C, which has a load carrying capacity of 1820# @ 50 psi is adequate.  But let's check other sizing issues:

                    
            Diameter / Width / Rim Width
7.00-15        29.6" / 7.95" / 5 to 6 1/2"
ST205/75R15    27.1" / 7.99" / 5" to 6 1/2"

The only thing that doesn't seem to work is the diameter.

For comparison:  ST227/75R15 28.3" / 8.78"  / 6 to 7"