Comparison
245/45 R17 vs 255/35 R18
Plus-sizing from 245/45 R17 to 255/35 R18 keeps overall diameter close to factory while opening room for a larger 18-inch wheel. This wheel and tire pairing trims or stretches rolling diameter by a small margin. The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 255/35 R18 is 16.6 mm shorter than 245/45 R17, shifting the speedometer by -2.54%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-16.6 mm
-2.54%
Speedometer at 100
97.5 km/h
-2.54% error
Ground clearance
-8.3 mm
ride height delta
Sidewall change
-21.0 mm
revs/km: 500.7
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/compare/245-45-r17-vs-255-35-r18Detailed comparison
| Metric | 245/45 R17 | 255/35 R18 | Difference |
|---|---|---|---|
| Overall diameter | 652.3 mm | 635.7 mm | -16.6 mm (-2.54%) |
| Sidewall height | 110.3 mm | 89.3 mm | -21.0 mm |
| Circumference | 2.049 m | 1.997 m | -52.2 mm |
| Revs / km | 488.0 | 500.7 | +12.7 |
| Ground clearance | reference | -8.3 mm | -8.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.5 km/h | -2.54 km/h |
Verdict: excellent
Within ±3% — speedometer, ABS and traction control should behave normally.
Speedometer impact
At a true 100 km/h, your dashboard will read 97.5 km/h after switching to 255/35 R18 — a -2.54% offset. Use the speedometer error calculator to recheck for other indicated speeds, and the speedometer error guide for the full background.
Ground clearance change
The new tire's half-diameter changes ride height by -8.3 mm. Small differences are absorbed by suspension travel, but anything beyond ±10 mm can affect headlight aim, fender clearance and bump-stop margin. See the plus-sizing guide before committing.
Back to
245/45 R17
Back to
255/35 R18
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