Comparison
225/45 R19 vs 225/55 R18
225/55 R18 drops the rim from 19 to 18 inches versus 225/45 R19, trading wheel size for taller sidewall. This swap 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. More sidewall typically improves comfort and curb protection, especially on city streets. Minus-sizing keeps replacement costs down and opens up a wider range of winter and all-terrain tires. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 225/55 R18 is 19.6 mm taller than 225/45 R19, shifting the speedometer by +2.86%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+19.6 mm
2.86%
Speedometer at 100
102.9 km/h
+2.86% error
Ground clearance
+9.8 mm
ride height delta
Sidewall change
+22.5 mm
revs/km: 451.7
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/compare/225-45-r19-vs-225-55-r18Detailed comparison
| Metric | 225/45 R19 | 225/55 R18 | Difference |
|---|---|---|---|
| Overall diameter | 685.1 mm | 704.7 mm | +19.6 mm (+2.86%) |
| Sidewall height | 101.3 mm | 123.8 mm | +22.5 mm |
| Circumference | 2.152 m | 2.214 m | +61.6 mm |
| Revs / km | 464.6 | 451.7 | -12.9 |
| Ground clearance | reference | +9.8 mm | +9.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.9 km/h | +2.86 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 102.9 km/h after switching to 225/55 R18 — a +2.86% 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 +9.8 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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225/45 R19
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225/55 R18
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