215/55R17 vs 245/45R17
245/45R17 has an overall diameter of 652.3 mm (25.68") compared with 668.3 mm (26.31") for 215/55R17, a difference of -16.0 mm (-2.39 %). The sidewall changes by -8.0 mm, section width by +30 mm and ride height by -8.0 mm. Using the ETRTO rolling circumference, 215/55R17 turns 491 times per kilometre and 245/45R17 turns 503 times. With 245/45R17 fitted to a car calibrated for 215/55R17, an indicated 100 km/h is a true 97.6 km/h, and the odometer records 102.5 km for every 100 km driven. This is close to the commonly quoted 3 % tolerance, so check clearance and local rules.
Full comparison
| Measurement | 215/55R17 | 245/45R17 | Difference |
|---|---|---|---|
| Section width | 215 mm | 245 mm | +30 mm |
| Sidewall height | 118.3 mm | 110.3 mm | -8.0 mm |
| Rim diameter | 17" | 17" | 0.0" |
| Overall diameter | 668.3 mm (26.31") | 652.3 mm (25.68") | -16.0 mm (-2.39 %) |
| Static circumference | 2100 mm | 2049 mm | -50 mm |
| Rolling circumference (ETRTO) | 2038 mm | 1990 mm | -49 mm |
| Revs per km | 491 | 503 | +12 |
| Ride height | -8.0 mm | ||
| Inch equivalent | 26.3×8.5R17 | 25.7×9.6R17 | |
| Approved rim widths (approx.) | 6″–8″ | 7.5″–9″ |
Speedometer error
| Speedo reads | 40 | 50 | 60 | 80 | 100 | 110 |
|---|---|---|---|---|---|---|
| Actual speed (km/h) | 39.0 | 48.8 | 58.6 | 78.1 | 97.6 | 107.4 |
| Error (km/h) | -1.0 | -1.2 | -1.4 | -1.9 | -2.4 | -2.6 |
Assumes the speedo was accurate on 215/55R17. Odometer records 102.5 km for every 100 km actually driven.
- The 245/45R17 is 16 mm (2.39 %) smaller in diameter, so your speedo will read high and your odometer will over-record distance.
- Section width changes by +30 mm. Check guard, strut and inner-arch clearance and that the rim width is within the approved range for the new tyre.
Is 245/45R17 legal in Australia? More info needed
| Overall diameter (VSB 14 LS 4.2.4) Diameter change of -16.0 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 97.6 km/h (over-read 2.4 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 245/45R17 instead of 215/55R17?
Overall diameter changes by -16.0 mm (-2.39 %). 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 245/45R17?
Your speedo will read high by about 2.39 %. At an indicated 100 km/h you would actually be travelling 97.6 km/h, and at 110 km/h about 107.4 km/h.
What is the rolling circumference of 245/45R17?
Static circumference is 2049 mm; the ETRTO rolling circumference under load is about 1990 mm, which is 503 revolutions per kilometre.
245/45R17 in inches
245/45R17 is approximately 25.7×9.6R17: 25.7" tall, 9.6" wide, on a 17" rim, with a 4.3" sidewall.
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