Comparison
245/40 R20 vs 255/45 R19
255/45 R19 drops the rim from 20 to 19 inches versus 245/40 R20, trading wheel size for taller sidewall. This sizing approach preserves rolling diameter within a hair of the original.
The speedometer offset is mild and well inside what most cars can tolerate without recalibration. Extra sidewall absorbs impacts more readily — a sensible bias for daily commuting and broken pavement. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. The smaller wheel is also lighter and easier to find affordable winter rubber for. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 255/45 R19 is 8.1 mm taller than 245/40 R20, shifting the speedometer by +1.15%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+8.1 mm
1.15%
Speedometer at 100
101.2 km/h
+1.15% error
Ground clearance
+4.0 mm
ride height delta
Sidewall change
+16.8 mm
revs/km: 447.0
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/compare/245-40-r20-vs-255-45-r19Detailed comparison
| Metric | 245/40 R20 | 255/45 R19 | Difference |
|---|---|---|---|
| Overall diameter | 704.0 mm | 712.1 mm | +8.1 mm (+1.15%) |
| Sidewall height | 98.0 mm | 114.8 mm | +16.8 mm |
| Circumference | 2.212 m | 2.237 m | +25.4 mm |
| Revs / km | 452.1 | 447.0 | -5.1 |
| Ground clearance | reference | +4.0 mm | +4.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.2 km/h | +1.15 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 101.2 km/h after switching to 255/45 R19 — a +1.15% 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 +4.0 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
245/40 R20
Back to
255/45 R19
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