245/40R19 vs 255/40R19 at a glance
| Measure | 245/40R19 (current) | 255/40R19 (new) | Difference |
|---|---|---|---|
| Overall height | 26.72 in | 27.03 in | +0.31 in (+1.18%) |
| Width | 9.65 in (245 mm) | 10.04 in (255 mm) | +10 mm |
| Sidewall | 3.86 in | 4.02 in | +0.16 in |
| Wheel | 19 in | 19 in | +0 in |
| Circumference | 83.9 in | 84.9 in | +1.0 in |
| Revs per mile | 754.9 | 746.1 | −8.8 |
Verdict: close match
Within the 3% rule of thumb, so the speedometer, gearing and ride height change little. Going from 245/40R19 to 255/40R19 is a 1.2% increase in overall height (+0.31 in), and the vehicle sits about 0.16 in higher. The tire is 10 mm wider. The 3% rule of thumb comes from Discount Tire and 1010tires; it is not a guarantee of fit.
True speed and odometer
| Speedometer shows | You are really doing | Difference |
|---|---|---|
| 35 mph | 35.4 mph | +0.4 mph |
| 45 mph | 45.5 mph | +0.5 mph |
| 55 mph | 55.6 mph | +0.6 mph |
| 60 mph | 60.7 mph | +0.7 mph |
| 65 mph | 65.8 mph | +0.8 mph |
| 70 mph | 70.8 mph | +0.8 mph |
| 75 mph | 75.9 mph | +0.9 mph |
Odometer: 1,000 indicated miles is 1,012 real miles, and 10,000 is 10,118.
The math
245/40R19: 19 + 2 × (245 × 40% ÷ 25.4) = 26.72 in. 255/40R19: 19 + 2 × (255 × 40% ÷ 25.4) = 27.03 in. Change = 27.03 ÷ 26.72 − 1 = +1.18%. True speed at 60 = 60 × 27.03 ÷ 26.72 = 60.71 mph.
Check next
- Regear and RPM at cruise for this swap
- Speedometer and odometer correction
- Other sizes within ±3% of 245/40R19
Calculated from the size alone. Real tires vary a little by brand and model, and the loaded radius is a bit smaller. Confirm the wheel width range, clearance, load index and speed rating for your vehicle. See how to read a tire size, the load index chart and the speed rating chart.
Size pages: 245/40R19 · 255/40R19. More swaps: all tire size comparisons.