Compare 195/50 R16 vs 195/55 R16 Tire Size and Comparison Calculator calculate tire diameter from code and compare speedometer differences for tire sizes. The first number 195 is the tire width in millimeters. Tire size comparison in inches 185/55 R15 vs 195/55 R15 Calculate CM INCHES If your speedometer reads: Real speed is: Size difference between 185/55 R15 and 195/55 R15 tires. In the tire comparison table above, you can see a detailed calculation of the size difference between 185/55 R15 and 195/55 R15 tire. Tire size comparison 195/65 R15 vs 205/65 R15 Calculate CM INCHES If your speedometer reads: Real speed is: Size difference between 195/65 R15 and 205/65 R15 tires. In the tire comparison table above, you can see a detailed calculation of the size difference between 195/65 R15 and 205/65 R15 tire. Tire size comparison 195/50 R15 vs 195/60 R15 Calculate CM INCHES If your speedometer reads: Real speed is: Size difference between 195/50 R15 and 195/60 R15 tires. In the tire comparison table above, you can see a detailed calculation of the size difference between 195/50 R15 and 195/60 R15 tire. Most Popular 205/65-R15 Comparisons. vs 195/65-15 vs 205/70-15 vs 215/65-15 vs 205/60-16 vs 215/70-15 vs 215/60-15 vs 205/55-16 vs 215/60-16. 195/65-R15 tires are 0.51 inches (13 mm) smaller in diameter than 205/65-R15 tires and the speedometer difference is 2.0%. sdIfk8.