Comparison
245/40 R20 vs 255/50 R19
Minus-sizing from 245/40 R20 to 255/50 R19 pairs a smaller 19-inch wheel with more rubber between the rim and road. This tire combination noticeably changes overall diameter compared to OEM. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. More sidewall typically improves comfort and curb protection, especially on city streets. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 255/50 R19 is 33.6 mm taller than 245/40 R20, shifting the speedometer by +4.77%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+33.6 mm
4.77%
Speedometer at 100
104.8 km/h
+4.77% error
Ground clearance
+16.8 mm
ride height delta
Sidewall change
+29.5 mm
revs/km: 431.5
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/compare/245-40-r20-vs-255-50-r19Detailed comparison
| Metric | 245/40 R20 | 255/50 R19 | Difference |
|---|---|---|---|
| Overall diameter | 704.0 mm | 737.6 mm | +33.6 mm (+4.77%) |
| Sidewall height | 98.0 mm | 127.5 mm | +29.5 mm |
| Circumference | 2.212 m | 2.317 m | +105.6 mm |
| Revs / km | 452.1 | 431.5 | -20.6 |
| Ground clearance | reference | +16.8 mm | +16.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 104.8 km/h | +4.77 km/h |
Verdict: warning
Between 3% and 5% — noticeable speedometer drift; recalibration may be advisable.
Speedometer impact
At a true 100 km/h, your dashboard will read 104.8 km/h after switching to 255/50 R19 — a +4.77% 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 +16.8 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.
Back to
245/40 R20
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255/50 R19
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