Comparison
225/40 R18 vs 225/55 R16
Minus-sizing from 225/40 R18 to 225/55 R16 pairs a smaller 16-inch wheel with more rubber between the rim and road. This tire combination moves rolling diameter a touch off the original spec. More sidewall typically improves comfort and curb protection, especially on city streets.
The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 225/55 R16 is 16.7 mm taller than 225/40 R18, shifting the speedometer by +2.62%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+16.7 mm
2.62%
Speedometer at 100
102.6 km/h
+2.62% error
Ground clearance
+8.3 mm
ride height delta
Sidewall change
+33.8 mm
revs/km: 486.8
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/compare/225-40-r18-vs-225-55-r16Detailed comparison
| Metric | 225/40 R18 | 225/55 R16 | Difference |
|---|---|---|---|
| Overall diameter | 637.2 mm | 653.9 mm | +16.7 mm (+2.62%) |
| Sidewall height | 90.0 mm | 123.8 mm | +33.8 mm |
| Circumference | 2.002 m | 2.054 m | +52.5 mm |
| Revs / km | 499.5 | 486.8 | -12.8 |
| Ground clearance | reference | +8.3 mm | +8.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.6 km/h | +2.62 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 102.6 km/h after switching to 225/55 R16 — a +2.62% 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.
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225/40 R18
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225/55 R16
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