Comparison
215/55 R17 vs 245/45 R18
Plus-sizing from 215/55 R17 to 245/45 R18 keeps overall diameter close to factory while opening room for a larger 18-inch wheel. This sizing approach barely shifts the rolling circumference. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement.
The speedometer offset is mild and well inside what most cars can tolerate without recalibration. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 245/45 R18 is 9.4 mm taller than 215/55 R17, shifting the speedometer by +1.41%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+9.4 mm
1.41%
Speedometer at 100
101.4 km/h
+1.41% error
Ground clearance
+4.7 mm
ride height delta
Sidewall change
-8.0 mm
revs/km: 469.7
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/compare/215-55-r17-vs-245-45-r18Detailed comparison
| Metric | 215/55 R17 | 245/45 R18 | Difference |
|---|---|---|---|
| Overall diameter | 668.3 mm | 677.7 mm | +9.4 mm (+1.41%) |
| Sidewall height | 118.3 mm | 110.3 mm | -8.0 mm |
| Circumference | 2.100 m | 2.129 m | +29.5 mm |
| Revs / km | 476.3 | 469.7 | -6.6 |
| Ground clearance | reference | +4.7 mm | +4.7 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.4 km/h | +1.41 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 101.4 km/h after switching to 245/45 R18 — a +1.41% 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 +4.7 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.
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215/55 R17
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245/45 R18
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