Tire Size Calculator

Tire Size Finder (optional):

Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
235/45r21 vs 155/85r18 Tire Comparison Side By Side
  235/45-21 155/85-18 Difference
Diameter inches (mm) 29.33 (744.9) 28.37 (720.7) -0.95 (-24.2) -3.2%
Width inches (mm) 9.25 (235) 6.1 (155) -3.15 (-80) -34%
Circum. inches (mm) 92.13 (2340.17) 89.14 (2264.15) -2.99 (-76.03) -3.2%
Sidewall Height inches (mm) 4.16 (105.75) 5.19 (131.75) 1.02 (26) 24.6%
Revolutions per mile (km) 687.7 (427.32) 710.8 (441.67) 23.09 (14.35) 3.4%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.35 mph (31.14 km/h)
25 mph (40.23 km/h)24.19 mph (38.93 km/h)
30 mph (48.28 km/h)29.03 mph (46.71 km/h)
35 mph (56.33 km/h)33.86 mph (54.5 km/h)
40 mph (64.37 km/h)38.7 mph (62.28 km/h)
45 mph (72.42 km/h)43.54 mph (70.07 km/h)
50 mph (80.47 km/h)48.38 mph (77.85 km/h)
55 mph (88.51 km/h)53.21 mph (85.64 km/h)
60 mph (96.56 km/h)58.05 mph (93.42 km/h)
65 mph (104.61 km/h)62.89 mph (101.21 km/h)
70 mph (112.65 km/h)67.73 mph (108.99 km/h)
75 mph (120.7 km/h)72.56 mph (116.78 km/h)
80 mph (128.75 km/h)77.4 mph (124.57 km/h)
85 mph (136.79 km/h)82.24 mph (132.35 km/h)
90 mph (144.84 km/h)87.08 mph (140.14 km/h)
95 mph (152.89 km/h)91.91 mph (147.92 km/h)
100 mph (160.93 km/h)96.75 mph (155.71 km/h)

Gear Ratio / RPMs for New Tire (@ 65 mph)
2.35 2.73 2.94 3.07 3.21 3.31 3.42 3.55 3.73 3.91 4.11 4.27 4.56 4.88 5.13 5.29 5.38 5.71 6.17 7.17
18092101226323632471254826322733287130103164328735103756394940724141439547495519
Better Fuel Economy Factory Ratios Increased Power

Most Popular 235/45-R21 Comparisons

To Top