Comparison
245/45 R18 vs 255/40 R19
Switching from 245/45 R18 to 255/40 R19 is a plus-1 upgrade that wraps a shorter sidewall around a larger 19-inch wheel. This wheel and tire pairing lands within OEM rolling-diameter tolerance.
The speedometer offset is mild and well inside what most cars can tolerate without recalibration. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. Many drivers pick this direction primarily for appearance — the bigger rim simply looks more aggressive. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 255/40 R19 is 8.9 mm taller than 245/45 R18, shifting the speedometer by +1.31%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+8.9 mm
1.31%
Speedometer at 100
101.3 km/h
+1.31% error
Ground clearance
+4.4 mm
ride height delta
Sidewall change
-8.3 mm
revs/km: 463.6
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/compare/245-45-r18-vs-255-40-r19Detailed comparison
| Metric | 245/45 R18 | 255/40 R19 | Difference |
|---|---|---|---|
| Overall diameter | 677.7 mm | 686.6 mm | +8.9 mm (+1.31%) |
| Sidewall height | 110.3 mm | 102.0 mm | -8.3 mm |
| Circumference | 2.129 m | 2.157 m | +28.0 mm |
| Revs / km | 469.7 | 463.6 | -6.1 |
| Ground clearance | reference | +4.4 mm | +4.4 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.3 km/h | +1.31 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 101.3 km/h after switching to 255/40 R19 — a +1.31% 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 +4.4 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
245/45 R18
Back to
255/40 R19
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