-4.74%Borderline — noticeable speedometer/odometer error
Speedometer error
With a speedometer calibrated to 245/40R20, fitting 235/40R19 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 38.1 km/h | 25 mph | 24 mph |
| 60 km/h | 57.2 km/h | 37 mph | 36 mph |
| 80 km/h | 76.2 km/h | 50 mph | 47 mph |
| 100 km/h | 95.3 km/h | 62 mph | 59 mph |
| 120 km/h | 114.3 km/h | 75 mph | 71 mph |
Full comparison
245/40R20
Overall diameter704.0 mm · 27.72 in
Section width245 mm · 9.65 in
Sidewall height98.0 mm · 3.86 in
Circumference2211.7 mm · 87.1 in
Revolutions per mile728
Revolutions per km452
235/40R19
Overall diameter670.6 mm · 26.40 in
Section width235 mm · 9.25 in
Sidewall height94.0 mm · 3.70 in
Circumference2106.8 mm · 82.9 in
Revolutions per mile764
Revolutions per km475
-4.74%Borderline — noticeable speedometer/odometer error
Original
Overall diameter704 mm · 27.72 in
Sidewall height98 mm
Circumference2,211.7 mm
Revolutions / mile727.7
New
Overall diameter670.6 mm · 26.4 in
Sidewall height94 mm
Circumference2,106.8 mm
Revolutions / mile763.9
Speedometer & odometer error
The new tire changes overall diameter by -4.74%. With a speedometer calibrated to the original tire, that same percentage is how far the speedometer and odometer read off — a taller tire means your true speed is higher than indicated and the odometer under-counts distance.
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 38.1 km/h | 25 mph | 24 mph |
| 60 km/h | 57.2 km/h | 37 mph | 36 mph |
| 80 km/h | 76.2 km/h | 50 mph | 47 mph |
| 100 km/h | 95.3 km/h | 62 mph | 59 mph |
| 120 km/h | 114.3 km/h | 75 mph | 71 mph |
See individual specs: 245/40R20 · 235/40R19. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.