Comparison
215/50 R17 vs 255/40 R18
Plus-sizing from 215/50 R17 to 255/40 R18 keeps overall diameter close to factory while opening room for a larger 18-inch wheel. This wheel and tire pairing moves rolling diameter a touch off the original spec. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides.
Expect a slight but noticeable shift in indicated speed compared to the original tires. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 255/40 R18 is 14.4 mm taller than 215/50 R17, shifting the speedometer by +2.23%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+14.4 mm
2.23%
Speedometer at 100
102.2 km/h
+2.23% error
Ground clearance
+7.2 mm
ride height delta
Sidewall change
-5.5 mm
revs/km: 481.4
Permalink for this comparison:
/compare/215-50-r17-vs-255-40-r18Detailed comparison
| Metric | 215/50 R17 | 255/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 646.8 mm | 661.2 mm | +14.4 mm (+2.23%) |
| Sidewall height | 107.5 mm | 102.0 mm | -5.5 mm |
| Circumference | 2.032 m | 2.077 m | +45.2 mm |
| Revs / km | 492.1 | 481.4 | -10.7 |
| Ground clearance | reference | +7.2 mm | +7.2 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.2 km/h | +2.23 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 102.2 km/h after switching to 255/40 R18 — a +2.23% 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 +7.2 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
215/50 R17
Back to
255/40 R18
Drivers also compare
Closely-related fitments and plus-size swaps for 215/50 R17 and 255/40 R18.
225/45 R18 vs 255/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.23%
215/50 R17 vs 235/45 R17
Wider variation on the same rim — more grip, less clearance.
Δ 0.54%
215/50 R17 vs 245/45 R17
Wider variation on the same rim — more grip, less clearance.
Δ 0.85%
235/45 R18 vs 255/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.12%
255/40 R18 vs 265/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.21%
245/40 R18 vs 255/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.22%
215/50 R17 vs 225/50 R17
Wider variation on the same rim — more grip, less clearance.
Δ 1.55%
205/50 R17 vs 215/50 R17
Wider variation on the same rim — more grip, less clearance.
Δ 1.57%
Related topics