255/40R19 vs 235/40R19
235/40R19 has an overall diameter of 670.6 mm (26.40") compared with 686.6 mm (27.03") for 255/40R19, a difference of -16.0 mm (-2.33 %). The sidewall changes by -8.0 mm, section width by -20 mm and ride height by -8.0 mm. Using the ETRTO rolling circumference, 255/40R19 turns 478 times per kilometre and 235/40R19 turns 489 times. With 235/40R19 fitted to a car calibrated for 255/40R19, an indicated 100 km/h is a true 97.7 km/h, and the odometer records 102.4 km for every 100 km driven. This is close to the commonly quoted 3 % tolerance, so check clearance and local rules.
Full comparison
| Measurement | 255/40R19 | 235/40R19 | Difference |
|---|---|---|---|
| Section width | 255 mm | 235 mm | -20 mm |
| Sidewall height | 102.0 mm | 94.0 mm | -8.0 mm |
| Rim diameter | 19" | 19" | 0.0" |
| Overall diameter | 686.6 mm (27.03") | 670.6 mm (26.40") | -16.0 mm (-2.33 %) |
| Static circumference | 2157 mm | 2107 mm | -50 mm |
| Rolling circumference (ETRTO) | 2094 mm | 2045 mm | -49 mm |
| Revs per km | 478 | 489 | +11 |
| Ride height | -8.0 mm | ||
| Inch equivalent | 27x10R19 | 26.4×9.3R19 | |
| Approved rim widths (approx.) | 8.5″–10″ | 8″–9.5″ |
Speedometer error
| Speedo reads | 40 | 50 | 60 | 80 | 100 | 110 |
|---|---|---|---|---|---|---|
| Actual speed (km/h) | 39.1 | 48.8 | 58.6 | 78.1 | 97.7 | 107.4 |
| Error (km/h) | -0.9 | -1.2 | -1.4 | -1.9 | -2.3 | -2.6 |
Assumes the speedo was accurate on 255/40R19. Odometer records 102.4 km for every 100 km actually driven.
- The 235/40R19 is 16 mm (2.33 %) smaller in diameter, so your speedo will read high and your odometer will over-record distance.
- Section width changes by -20 mm. Check guard, strut and inner-arch clearance and that the rim width is within the approved range for the new tyre.
Is 235/40R19 legal in Australia? More info needed
| Overall diameter (VSB 14 LS 4.2.4) Diameter change of -16.0 mm is within the +15 mm / -26 mm allowance for a passenger car (MA/MB) (measured against the largest size the manufacturer designates for the model). | OK |
| Speedometer (ADR 18/03) A smaller tyre makes the speedo read high: at an indicated 100 km/h you would be doing 97.7 km/h (over-read 2.3 km/h; ADR 18 allows up to 13.8 km/h at that speed). | OK |
| Load index (tyre placard / ADR 42) Enter the placard load index and the replacement tyre load index to check. | ? |
| Speed rating (tyre placard / ADR 42) Enter the placard speed rating and the replacement tyre speed rating to check. | ? |
Frequently asked
Can I fit 235/40R19 instead of 255/40R19?
Overall diameter changes by -16.0 mm (-2.33 %). That is close to the 3 % rule of thumb; it may fit, but check guard, strut and brake clearance and your local rules. In Australia VSB 14 allows up to +15 mm for passenger cars and +50 mm for 4WDs/goods vehicles without certification.
How much will my speedo be out with 235/40R19?
Your speedo will read high by about 2.33 %. At an indicated 100 km/h you would actually be travelling 97.7 km/h, and at 110 km/h about 107.4 km/h.
What is the rolling circumference of 235/40R19?
Static circumference is 2107 mm; the ETRTO rolling circumference under load is about 2045 mm, which is 489 revolutions per kilometre.
235/40R19 in inches
235/40R19 is approximately 26.4×9.3R19: 26.4" tall, 9.3" wide, on a 19" rim, with a 3.7" sidewall.
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