Comparison
255/40 R18 vs 285/35 R19
285/35 R19 is a plus-1 alternative to 255/40 R18 — the bigger wheel shows through a thinner sidewall. This alternative fitment moves rolling diameter well outside the usual OEM tolerance. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input.
The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 285/35 R19 is 20.9 mm taller than 255/40 R18, shifting the speedometer by +3.16%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+20.9 mm
3.16%
Speedometer at 100
103.2 km/h
+3.16% error
Ground clearance
+10.4 mm
ride height delta
Sidewall change
-2.3 mm
revs/km: 466.7
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/compare/255-40-r18-vs-285-35-r19Detailed comparison
| Metric | 255/40 R18 | 285/35 R19 | Difference |
|---|---|---|---|
| Overall diameter | 661.2 mm | 682.1 mm | +20.9 mm (+3.16%) |
| Sidewall height | 102.0 mm | 99.8 mm | -2.3 mm |
| Circumference | 2.077 m | 2.143 m | +65.7 mm |
| Revs / km | 481.4 | 466.7 | -14.8 |
| Ground clearance | reference | +10.4 mm | +10.4 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.2 km/h | +3.16 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 103.2 km/h after switching to 285/35 R19 — a +3.16% 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 +10.4 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.
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255/40 R18
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285/35 R19
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