Comparison
245/35 R19 vs 255/40 R18
255/40 R18 drops the rim from 19 to 18 inches versus 245/35 R19, trading wheel size for taller sidewall. This setup 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.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 255/40 R18 is 7.1 mm taller than 245/35 R19, shifting the speedometer by +1.09%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+7.1 mm
1.09%
Speedometer at 100
101.1 km/h
+1.09% error
Ground clearance
+3.6 mm
ride height delta
Sidewall change
+16.3 mm
revs/km: 481.4
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/compare/245-35-r19-vs-255-40-r18Detailed comparison
| Metric | 245/35 R19 | 255/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 654.1 mm | 661.2 mm | +7.1 mm (+1.09%) |
| Sidewall height | 85.8 mm | 102.0 mm | +16.3 mm |
| Circumference | 2.055 m | 2.077 m | +22.3 mm |
| Revs / km | 486.6 | 481.4 | -5.2 |
| Ground clearance | reference | +3.6 mm | +3.6 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.1 km/h | +1.09 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 101.1 km/h after switching to 255/40 R18 — a +1.09% 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 +3.6 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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245/35 R19
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255/40 R18
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