Comparison
225/55 R17 vs 255/45 R18
Plus-sizing from 225/55 R17 to 255/45 R18 keeps overall diameter close to factory while opening room for a larger 18-inch wheel. This setup preserves rolling diameter within a hair of the original. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input.
The speedometer offset is mild and well inside what most cars can tolerate without recalibration. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 255/45 R18 is 7.4 mm taller than 225/55 R17, shifting the speedometer by +1.09%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+7.4 mm
1.09%
Speedometer at 100
101.1 km/h
+1.09% error
Ground clearance
+3.7 mm
ride height delta
Sidewall change
-9.0 mm
revs/km: 463.5
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/compare/225-55-r17-vs-255-45-r18Detailed comparison
| Metric | 225/55 R17 | 255/45 R18 | Difference |
|---|---|---|---|
| Overall diameter | 679.3 mm | 686.7 mm | +7.4 mm (+1.09%) |
| Sidewall height | 123.8 mm | 114.8 mm | -9.0 mm |
| Circumference | 2.134 m | 2.157 m | +23.2 mm |
| Revs / km | 468.6 | 463.5 | -5.0 |
| Ground clearance | reference | +3.7 mm | +3.7 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.1 km/h | +1.09 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 101.1 km/h after switching to 255/45 R18 — a +1.09% 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 +3.7 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
225/55 R17
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255/45 R18
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