Comparison
215/55 R16 vs 255/40 R18
Switching from 215/55 R16 to 255/40 R18 is a plus-2 upgrade that wraps a shorter sidewall around a larger 18-inch wheel. This tire combination trims or stretches rolling diameter by a small margin. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides.
Expect a slight but noticeable shift in indicated speed compared to the original tires. 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: 255/40 R18 is 18.3 mm taller than 215/55 R16, shifting the speedometer by +2.85%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+18.3 mm
2.85%
Speedometer at 100
102.8 km/h
+2.85% error
Ground clearance
+9.2 mm
ride height delta
Sidewall change
-16.3 mm
revs/km: 481.4
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/compare/215-55-r16-vs-255-40-r18Detailed comparison
| Metric | 215/55 R16 | 255/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 642.9 mm | 661.2 mm | +18.3 mm (+2.85%) |
| Sidewall height | 118.3 mm | 102.0 mm | -16.3 mm |
| Circumference | 2.020 m | 2.077 m | +57.5 mm |
| Revs / km | 495.1 | 481.4 | -13.7 |
| Ground clearance | reference | +9.2 mm | +9.2 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.8 km/h | +2.85 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 102.8 km/h after switching to 255/40 R18 — a +2.85% 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 +9.2 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
215/55 R16
Back to
255/40 R18
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