Comparison
255/35 R19 vs 265/40 R18
Going from 255/35 R19 to 265/40 R18 is a minus-1 setup that adds sidewall on a smaller 18-inch wheel. This swap preserves rolling diameter within a hair of the original. The taller sidewall adds cushioning over potholes and rougher roads, with a softer overall ride.
Speedometer drift stays small enough that most drivers won't notice it day to day. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 265/40 R18 is 8.1 mm taller than 255/35 R19, shifting the speedometer by +1.23%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+8.1 mm
1.23%
Speedometer at 100
101.2 km/h
+1.23% error
Ground clearance
+4.1 mm
ride height delta
Sidewall change
+16.8 mm
revs/km: 475.7
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/compare/255-35-r19-vs-265-40-r18Detailed comparison
| Metric | 255/35 R19 | 265/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 661.1 mm | 669.2 mm | +8.1 mm (+1.23%) |
| Sidewall height | 89.3 mm | 106.0 mm | +16.8 mm |
| Circumference | 2.077 m | 2.102 m | +25.4 mm |
| Revs / km | 481.5 | 475.7 | -5.8 |
| Ground clearance | reference | +4.1 mm | +4.1 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.2 km/h | +1.23 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 265/40 R18 — a +1.23% 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 +4.1 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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255/35 R19
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265/40 R18
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