255/60R18 vs 275/55R19
275/55R19 has an overall diameter of 785.1 mm (30.91") compared with 763.2 mm (30.05") for 255/60R18, a difference of +21.9 mm (+2.87 %). The sidewall changes by -1.7 mm, section width by +20 mm and ride height by +10.9 mm. Using the ETRTO rolling circumference, 255/60R18 turns 430 times per kilometre and 275/55R19 turns 418 times. With 275/55R19 fitted to a car calibrated for 255/60R18, an indicated 100 km/h is a true 102.9 km/h, and the odometer records 97.2 km for every 100 km driven. This is close to the commonly quoted 3 % tolerance, so check clearance and local rules.
Full comparison
| Measurement | 255/60R18 | 275/55R19 | Difference |
|---|---|---|---|
| Section width | 255 mm | 275 mm | +20 mm |
| Sidewall height | 153.0 mm | 151.3 mm | -1.7 mm |
| Rim diameter | 18" | 19" | +1.0" |
| Overall diameter | 763.2 mm (30.05") | 785.1 mm (30.91") | +21.9 mm (+2.87 %) |
| Static circumference | 2398 mm | 2466 mm | +69 mm |
| Rolling circumference (ETRTO) | 2328 mm | 2395 mm | +67 mm |
| Revs per km | 430 | 418 | -12 |
| Ride height | +10.9 mm | ||
| Inch equivalent | 30x10R18 | 30.9×10.8R19 | |
| Approved rim widths (approx.) | 7″–8.5″ | 7.5″–9.5″ |
Speedometer error
| Speedo reads | 40 | 50 | 60 | 80 | 100 | 110 |
|---|---|---|---|---|---|---|
| Actual speed (km/h) | 41.1 | 51.4 | 61.7 | 82.3 | 102.9 | 113.2 |
| Error (km/h) | +1.1 | +1.4 | +1.7 | +2.3 | +2.9 | +3.2 |
Assumes the speedo was accurate on 255/60R18. Odometer records 97.2 km for every 100 km actually driven.
- The 275/55R19 is 21.9 mm (2.87 %) 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.
- Rim diameter changes from 18" to 19", so new wheels are required.
Is 275/55R19 legal in Australia? Needs certification
| Overall diameter (VSB 14 LS 4.2.4) 275/55R19 is 21.9 mm larger than 255/60R18; 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 lower: at an indicated 100 km/h you would be doing 102.9 km/h. ADR 18 requires the speedo never to read below true speed, but factory speedos typically over-read by 2-6 %, so a 2.9 % 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 275/55R19 instead of 255/60R18?
Overall diameter changes by +21.9 mm (+2.87 %). 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 275/55R19?
Your speedo will read low by about 2.87 %. At an indicated 100 km/h you would actually be travelling 102.9 km/h, and at 110 km/h about 113.2 km/h.
What is the rolling circumference of 275/55R19?
Static circumference is 2466 mm; the ETRTO rolling circumference under load is about 2395 mm, which is 418 revolutions per kilometre.
275/55R19 in inches
275/55R19 is approximately 30.9×10.8R19: 30.9" tall, 10.8" wide, on a 19" rim, with a 6.0" sidewall.
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