Comparison
235/60 R16 vs 255/40 R18
Going from 235/60 R16 to 255/40 R18 steps up to a 18-inch rim while trimming sidewall to stay near OEM rolling diameter. This sizing approach swings rolling diameter far enough to feel on the road. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 255/40 R18 is 27.2 mm shorter than 235/60 R16, shifting the speedometer by -3.95%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-27.2 mm
-3.95%
Speedometer at 100
96.0 km/h
-3.95% error
Ground clearance
-13.6 mm
ride height delta
Sidewall change
-39.0 mm
revs/km: 481.4
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/compare/235-60-r16-vs-255-40-r18Detailed comparison
| Metric | 235/60 R16 | 255/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 688.4 mm | 661.2 mm | -27.2 mm (-3.95%) |
| Sidewall height | 141.0 mm | 102.0 mm | -39.0 mm |
| Circumference | 2.163 m | 2.077 m | -85.5 mm |
| Revs / km | 462.4 | 481.4 | +19.0 |
| Ground clearance | reference | -13.6 mm | -13.6 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.0 km/h | -3.95 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 96.0 km/h after switching to 255/40 R18 — a -3.95% 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 -13.6 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.
Back to
235/60 R16
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255/40 R18
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