265/60R18 vs 275/65R18
275/65R18 has an overall diameter of 814.7 mm (32.07") compared with 775.2 mm (30.52") for 265/60R18, a difference of +39.5 mm (+5.10 %). The sidewall changes by +19.8 mm, section width by +10 mm and ride height by +19.8 mm. Using the ETRTO rolling circumference, 265/60R18 turns 423 times per kilometre and 275/65R18 turns 402 times. With 275/65R18 fitted to a car calibrated for 265/60R18, an indicated 100 km/h is a true 105.1 km/h, and the odometer records 95.2 km for every 100 km driven. This exceeds the commonly quoted 3 % tolerance; check clearances, ABS/ESC calibration and local roadworthy rules (VSB 14 in Australia).
Full comparison
| Measurement | 265/60R18 | 275/65R18 | Difference |
|---|---|---|---|
| Section width | 265 mm | 275 mm | +10 mm |
| Sidewall height | 159.0 mm | 178.8 mm | +19.8 mm |
| Rim diameter | 18" | 18" | 0.0" |
| Overall diameter | 775.2 mm (30.52") | 814.7 mm (32.07") | +39.5 mm (+5.10 %) |
| Static circumference | 2435 mm | 2559 mm | +124 mm |
| Rolling circumference (ETRTO) | 2364 mm | 2485 mm | +120 mm |
| Revs per km | 423 | 402 | -21 |
| Ride height | +19.8 mm | ||
| Inch equivalent | 30.5×10.4R18 | 32.1×10.8R18 | |
| Approved rim widths (approx.) | 7.5″–9″ | 7.5″–9″ |
Speedometer error
| Speedo reads | 40 | 50 | 60 | 80 | 100 | 110 |
|---|---|---|---|---|---|---|
| Actual speed (km/h) | 42.0 | 52.5 | 63.1 | 84.1 | 105.1 | 115.6 |
| Error (km/h) | +2.0 | +2.5 | +3.1 | +4.1 | +5.1 | +5.6 |
Assumes the speedo was accurate on 265/60R18. Odometer records 95.2 km for every 100 km actually driven.
- The 275/65R18 is 39.5 mm (5.1 %) larger in diameter, so your speedo will read low and your odometer will under-record distance.
- Section width changes by +10 mm. Check guard, strut and inner-arch clearance and that the rim width is within the approved range for the new tyre.
- A diameter change over 3 % is outside the usual rule of thumb; check local roadworthy rules (in Australia see VSB 14 / NCOP Section LS) and ABS/ESC calibration.
Is 275/65R18 legal in Australia? Needs certification
| Overall diameter (VSB 14 LS 4.2.4) 275/65R18 is 39.5 mm larger than 265/60R18; the limit without certification for a passenger car (MA/MB) is +15 mm. Larger increases need an approved signatory / engineering certificate (modification code LS or state equivalent) and may not be permitted at all. | Cert. |
| Speedometer (ADR 18/03) A larger tyre makes the speedo read low: at an indicated 100 km/h you would be doing 105.1 km/h. ADR 18 requires the speedo never to read below true speed; a 5.1 % increase is unlikely to be absorbed by the factory over-read, so the speedo will need recalibration (correction module) and certification. | Cert. |
| 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 275/65R18 instead of 265/60R18?
Overall diameter changes by +39.5 mm (+5.10 %). That is outside the 3 % rule of thumb, so it may rub, upset ABS/ESC calibration and may not be legal without certification. 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 275/65R18?
Your speedo will read low by about 5.10 %. At an indicated 100 km/h you would actually be travelling 105.1 km/h, and at 110 km/h about 115.6 km/h.
What is the rolling circumference of 275/65R18?
Static circumference is 2559 mm; the ETRTO rolling circumference under load is about 2485 mm, which is 402 revolutions per kilometre.
275/65R18 in inches
275/65R18 is approximately 32.1×10.8R18: 32.1" tall, 10.8" wide, on a 18" rim, with a 7.0" sidewall.
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