265/75R16 vs 31×10.5R15
31×10.5R15 has an overall diameter of 787.4 mm (31.00") compared with 803.9 mm (31.65") for 265/75R16, a difference of -16.5 mm (-2.05 %). The sidewall changes by +4.4 mm, section width by +2 mm and ride height by -8.2 mm. Using the ETRTO rolling circumference, 265/75R16 turns 408 times per kilometre and 31×10.5R15 turns 416 times. With 31×10.5R15 fitted to a car calibrated for 265/75R16, an indicated 100 km/h is a true 97.9 km/h, and the odometer records 102.1 km for every 100 km driven. This is close to the commonly quoted 3 % tolerance, so check clearance and local rules.
Full comparison
| Measurement | 265/75R16 | 31×10.5R15 | Difference |
|---|---|---|---|
| Section width | 265 mm | 267 mm | +2 mm |
| Sidewall height | 198.8 mm | 203.2 mm | +4.4 mm |
| Rim diameter | 16" | 15" | -1.0" |
| Overall diameter | 803.9 mm (31.65") | 787.4 mm (31.00") | -16.5 mm (-2.05 %) |
| Static circumference | 2526 mm | 2474 mm | -52 mm |
| Rolling circumference (ETRTO) | 2452 mm | 2402 mm | -50 mm |
| Revs per km | 408 | 416 | +9 |
| Ride height | -8.2 mm | ||
| Inch equivalent | 31.6×10.4R16 | 31×10.5R15 | |
| Approved rim widths (approx.) | 7″–8.5″ | 7″–8.5″ |
Speedometer error
| Speedo reads | 40 | 50 | 60 | 80 | 100 | 110 |
|---|---|---|---|---|---|---|
| Actual speed (km/h) | 39.2 | 49.0 | 58.8 | 78.4 | 97.9 | 107.7 |
| Error (km/h) | -0.8 | -1.0 | -1.2 | -1.6 | -2.1 | -2.3 |
Assumes the speedo was accurate on 265/75R16. Odometer records 102.1 km for every 100 km actually driven.
- The 31×10.5R15 is 16.5 mm (2.05 %) smaller in diameter, so your speedo will read high and your odometer will over-record distance.
- Section width changes by +2 mm. Check guard, strut and inner-arch clearance and that the rim width is within the approved range for the new tyre.
- Rim diameter changes from 16" to 15", so new wheels are required.
Is 31×10.5R15 legal in Australia? More info needed
| Overall diameter (VSB 14 LS 4.2.4) Diameter change of -16.5 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 97.9 km/h (over-read 2.1 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 31×10.5R15 instead of 265/75R16?
Overall diameter changes by -16.5 mm (-2.05 %). 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 31×10.5R15?
Your speedo will read high by about 2.05 %. At an indicated 100 km/h you would actually be travelling 97.9 km/h, and at 110 km/h about 107.7 km/h.
What is the rolling circumference of 31×10.5R15?
Static circumference is 2474 mm; the ETRTO rolling circumference under load is about 2402 mm, which is 416 revolutions per kilometre.
31×10.5R15 in inches
31×10.5R15 is approximately 31×10.5R15: 31.0" tall, 10.5" wide, on a 15" rim, with a 8.0" sidewall.
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