Comparison
215/40 R18 vs 215/55 R16
215/55 R16 drops the rim from 18 to 16 inches versus 215/40 R18, trading wheel size for taller sidewall. This alternative fitment moves rolling diameter a touch off the original spec.
The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. The taller sidewall adds cushioning over potholes and rougher roads, with a softer overall ride. Minus-sizing keeps replacement costs down and opens up a wider range of winter and all-terrain tires. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 215/55 R16 is 13.7 mm taller than 215/40 R18, shifting the speedometer by +2.18%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+13.7 mm
2.18%
Speedometer at 100
102.2 km/h
+2.18% error
Ground clearance
+6.8 mm
ride height delta
Sidewall change
+32.3 mm
revs/km: 495.1
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/compare/215-40-r18-vs-215-55-r16Detailed comparison
| Metric | 215/40 R18 | 215/55 R16 | Difference |
|---|---|---|---|
| Overall diameter | 629.2 mm | 642.9 mm | +13.7 mm (+2.18%) |
| Sidewall height | 86.0 mm | 118.3 mm | +32.3 mm |
| Circumference | 1.977 m | 2.020 m | +43.0 mm |
| Revs / km | 505.9 | 495.1 | -10.8 |
| Ground clearance | reference | +6.8 mm | +6.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.2 km/h | +2.18 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 102.2 km/h after switching to 215/55 R16 — a +2.18% 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 +6.8 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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215/40 R18
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215/55 R16
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