this tire size conversion chart was found on tirerack.com

link below, here for convenience only, not updated
http://www.tirerack.com/tires/tiretech/45_conversionchart.html

Tire Size Conversion Chart

1949
to
1964 1965
to
1970 1970 to 1980 1960 - On 1980 - On

NUMERIC ALPHA NUMERIC* EURO-METRIC P-METRIC EURO-METRIC or P-METRIC

"90-" to "80"-series 78- to 50-series "82"-series 80-, 75-series 70-series 65-series 60-series 50-series

5.20-10 145R10 165/70R10

5.20-12 145R12 P145/80R12 165/70R12

5.60-12 6.00-12 155R12 P155/80R12

165/65R13

145R13

155R13 P155/80R13 175/70R13 195/60R13 215/50R13

5.60-13 6.00-13 A 165R13 P165/80R13 185/70R13 205/60R13

6.50-13 B 175R13 P175/80R13

C P185/80R13

7.00-13 D 185R13

195R13

5.60-14 6.00-14 145R14 175/65R14

6.00-14 6.45-14 155R14 175/70R14 185/65R14

B 165R14 P175/75R14 185/70R14 195/65R14 205/60R14

6.50-14 6.95-14 C 175R14 P185/75R14 195/70R14 215/60R14

D

7.00-14 7.35-14 E 185R14 P195/75R14 205/70R14 225/60R14 245/50R14

7.50-14 7.75-14 F 195R14 P205/75R14 215/70R14 235/60R14

8.00-14 8.25-14 G 205R14 P215/75R14 225/70R14 245/60R14 265/50R14

8.50-14 8.55-14 H 215R14 P225/75R14

9.00-14 J 225R14

9.50-14 L

5.60-15 A 155R15 P155/80R15 185/65R15 195/60R15

6.00-15 B 165R15 P165/80R15 185/70R15 195/65R15 205/60R15 225/50R15

6.50-15 6.85-15 C 175R15 195/70R15 205/65R15 215/60R15

D

7.35-15 E 185R15 P195/75R15 205/70R15 215/65R15 225/60R15

6.70-15 7.75-15 F 195R15 P205/75R15 215/70R15 235/60R15

8.15-15

7.10-15 G 205R15 P215/75R15 225/70R15 235/65R15 245/60R15 265/50R15

8.25-15

8.45-15

7.60-15 H 215R15 P225/75R15 235/70R15 255/60R15 275/50R15

8.55-15

8.00-15 8.85-15 J 225R15 P225/75R15 235/70R15 265/60R15

8.20-15 9.00-15 K

9.15-15 L 235R15 P235/75R15 255/70R15 275/60R15 295/50R15

N

* When replacing Alpha Numeric tires with Euro-metric or P-metric tires, look for the Euro-metric or P-metric size listed in the equivalent aspect ratio. For example, when replacing a FR78-14, you would look up the appropriate 75-series size, the 205/75R14. If replacing a FR70-14, you would look up the appropriate 70-series size, the 215/70R14. If replacing a FR60-14, you would look up the appropriate 60-series size, the 235/60R14.