235/60R18 vs 255/55R19Tire Size Comparison

Use Caution

The 3.2% diameter difference exceeds 3% and may affect speedometer accuracy.

235/60R18739mm dia255/55R19763mm dia+11.9mm

Comparison Details

Overall Diameter739.2 vs 763.1 mm (+23.9 mm)
Diameter Difference+3.23%
Section Width235 vs 255 mm (+20 mm)
Sidewall Height141.0 vs 140.3 mm (-0.7 mm)
Circumference2322.3 vs 2397.3 mm
Clearance Change+11.9 mm
Speedometer Error+3.23%
Revs/Mile693 vs 671

Speedometer Correction

When switching from 235/60R18 to 255/55R19, your speedometer will differ from actual speed.

SpeedometerActual SpeedDifference
30 km/h31.0 km/h+1.0 km/h
40 km/h41.3 km/h+1.3 km/h
50 km/h51.6 km/h+1.6 km/h
60 km/h61.9 km/h+1.9 km/h
70 km/h72.3 km/h+2.3 km/h
80 km/h82.6 km/h+2.6 km/h
90 km/h92.9 km/h+2.9 km/h
100 km/h103.2 km/h+3.2 km/h
110 km/h113.6 km/h+3.6 km/h
120 km/h123.9 km/h+3.9 km/h
130 km/h134.2 km/h+4.2 km/h

Vehicles Using These Sizes

Vehicles with 235/60R18

Vehicles with 255/55R19

Individual Tire Size Details

Practical Guidance

The 3.2% diameter difference between 235/60R18 and 255/55R19 exceeds the standard 3% tolerance. While physically possible, this change will cause noticeable speedometer error and may affect ABS and traction control calibration. Consult a tire professional before making this switch.

The 3% diameter tolerance is a widely accepted industry guideline referenced by the ETRTO and most vehicle manufacturers. When in doubt, consult your vehicle's owner's manual or a qualified tire professional. For U.S. tire safety standards and recalls, see the NHTSA Tire Safety page.

Frequently Asked Questions

Use Caution. The overall diameter differs by 3.23%, width changes by 20mm.

Speedometer error will be 3.23%. At an indicated 100 km/h, actual speed is about 103.2 km/h.

Ground clearance changes by +11.9mm per side.