275/65R18 vs 285/75R16
285/75R16 has an overall diameter of 833.9 mm (32.83") compared with 814.7 mm (32.07") for 275/65R18, a difference of +19.2 mm (+2.36 %). The sidewall changes by +35.0 mm, section width by +10 mm and ride height by +9.6 mm. Using the ETRTO rolling circumference, 275/65R18 turns 402 times per kilometre and 285/75R16 turns 393 times. With 285/75R16 fitted to a car calibrated for 275/65R18, an indicated 100 km/h is a true 102.4 km/h, and the odometer records 97.7 km for every 100 km driven. This is close to the commonly quoted 3 % tolerance, so check clearance and local rules.
Full comparison
| Measurement | 275/65R18 | 285/75R16 | Difference |
|---|---|---|---|
| Section width | 275 mm | 285 mm | +10 mm |
| Sidewall height | 178.8 mm | 213.8 mm | +35.0 mm |
| Rim diameter | 18" | 16" | -2.0" |
| Overall diameter | 814.7 mm (32.07") | 833.9 mm (32.83") | +19.2 mm (+2.36 %) |
| Static circumference | 2559 mm | 2620 mm | +60 mm |
| Rolling circumference (ETRTO) | 2485 mm | 2543 mm | +59 mm |
| Revs per km | 402 | 393 | -9 |
| Ride height | +9.6 mm | ||
| Inch equivalent | 32.1×10.8R18 | 32.8×11.2R16 | |
| Approved rim widths (approx.) | 7.5″–9″ | 7.5″–9″ |
Speedometer error
| Speedo reads | 40 | 50 | 60 | 80 | 100 | 110 |
|---|---|---|---|---|---|---|
| Actual speed (km/h) | 40.9 | 51.2 | 61.4 | 81.9 | 102.4 | 112.6 |
| Error (km/h) | +0.9 | +1.2 | +1.4 | +1.9 | +2.4 | +2.6 |
Assumes the speedo was accurate on 275/65R18. Odometer records 97.7 km for every 100 km actually driven.
- The 285/75R16 is 19.2 mm (2.36 %) 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.
- Rim diameter changes from 18" to 16", so new wheels are required.
Is 285/75R16 legal in Australia? Needs certification
| Overall diameter (VSB 14 LS 4.2.4) 285/75R16 is 19.2 mm larger than 275/65R18; 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 lower: at an indicated 100 km/h you would be doing 102.4 km/h. ADR 18 requires the speedo never to read below true speed, but factory speedos typically over-read by 2-6 %, so a 2.4 % increase is usually absorbed. Verify with a GPS speed app after fitting. | Verify |
| 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 285/75R16 instead of 275/65R18?
Overall diameter changes by +19.2 mm (+2.36 %). 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 285/75R16?
Your speedo will read low by about 2.36 %. At an indicated 100 km/h you would actually be travelling 102.4 km/h, and at 110 km/h about 112.6 km/h.
What is the rolling circumference of 285/75R16?
Static circumference is 2620 mm; the ETRTO rolling circumference under load is about 2543 mm, which is 393 revolutions per kilometre.
285/75R16 in inches
285/75R16 is approximately 32.8×11.2R16: 32.8" tall, 11.2" wide, on a 16" rim, with a 8.4" sidewall.
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