265/65R17 vs 285/70R17
285/70R17 has an overall diameter of 830.8 mm (32.71") compared with 776.3 mm (30.56") for 265/65R17, a difference of +54.5 mm (+7.02 %). The sidewall changes by +27.3 mm, section width by +20 mm and ride height by +27.3 mm. Using the ETRTO rolling circumference, 265/65R17 turns 422 times per kilometre and 285/70R17 turns 395 times. With 285/70R17 fitted to a car calibrated for 265/65R17, an indicated 100 km/h is a true 107 km/h, and the odometer records 93.4 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 | 265/65R17 | 285/70R17 | Difference |
|---|---|---|---|
| Section width | 265 mm | 285 mm | +20 mm |
| Sidewall height | 172.3 mm | 199.5 mm | +27.3 mm |
| Rim diameter | 17" | 17" | 0.0" |
| Overall diameter | 776.3 mm (30.56") | 830.8 mm (32.71") | +54.5 mm (+7.02 %) |
| Static circumference | 2439 mm | 2610 mm | +171 mm |
| Rolling circumference (ETRTO) | 2368 mm | 2534 mm | +166 mm |
| Revs per km | 422 | 395 | -28 |
| Ride height | +27.3 mm | ||
| Inch equivalent | 30.6×10.4R17 | 32.7×11.2R17 | |
| Approved rim widths (approx.) | 7.5″–9″ | 8″–9.5″ |
Speedometer error
| Speedo reads | 40 | 50 | 60 | 80 | 100 | 110 |
|---|---|---|---|---|---|---|
| Actual speed (km/h) | 42.8 | 53.5 | 64.2 | 85.6 | 107.0 | 117.7 |
| Error (km/h) | +2.8 | +3.5 | +4.2 | +5.6 | +7.0 | +7.7 |
Assumes the speedo was accurate on 265/65R17. Odometer records 93.4 km for every 100 km actually driven.
- The 285/70R17 is 54.5 mm (7.02 %) larger in diameter, so your speedo will read low and your odometer will under-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.
- 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 285/70R17 legal in Australia? Needs certification
| Overall diameter (VSB 14 LS 4.2.4) 285/70R17 is 54.5 mm larger than 265/65R17; 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 107.0 km/h. ADR 18 requires the speedo never to read below true speed; a 7.0 % 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 285/70R17 instead of 265/65R17?
Overall diameter changes by +54.5 mm (+7.02 %). 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 285/70R17?
Your speedo will read low by about 7.02 %. At an indicated 100 km/h you would actually be travelling 107 km/h, and at 110 km/h about 117.7 km/h.
What is the rolling circumference of 285/70R17?
Static circumference is 2610 mm; the ETRTO rolling circumference under load is about 2534 mm, which is 395 revolutions per kilometre.
285/70R17 in inches
285/70R17 is approximately 32.7×11.2R17: 32.7" tall, 11.2" wide, on a 17" rim, with a 7.9" sidewall.
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