Comparison
215/65 R16 vs 255/40 R18
Plus-sizing from 215/65 R16 to 255/40 R18 keeps overall diameter close to factory while opening room for a larger 18-inch wheel. This sizing approach swings rolling diameter far enough to feel on the road. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input.
Indicated speed will drift far enough that recalibration is worth considering. 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: 255/40 R18 is 24.7 mm shorter than 215/65 R16, shifting the speedometer by -3.60%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-24.7 mm
-3.60%
Speedometer at 100
96.4 km/h
-3.60% error
Ground clearance
-12.3 mm
ride height delta
Sidewall change
-37.8 mm
revs/km: 481.4
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/compare/215-65-r16-vs-255-40-r18Detailed comparison
| Metric | 215/65 R16 | 255/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 685.9 mm | 661.2 mm | -24.7 mm (-3.60%) |
| Sidewall height | 139.8 mm | 102.0 mm | -37.8 mm |
| Circumference | 2.155 m | 2.077 m | -77.6 mm |
| Revs / km | 464.1 | 481.4 | +17.3 |
| Ground clearance | reference | -12.3 mm | -12.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.4 km/h | -3.60 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 96.4 km/h after switching to 255/40 R18 — a -3.60% 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 -12.3 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
215/65 R16
Back to
255/40 R18
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