Comparison
215/50 R17 vs 255/35 R18
Going from 215/50 R17 to 255/35 R18 steps up to a 18-inch rim while trimming sidewall to stay near OEM rolling diameter. This setup shifts overall diameter slightly from OEM. Expect a slight but noticeable shift in indicated speed compared to the original tires. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 255/35 R18 is 11.1 mm shorter than 215/50 R17, shifting the speedometer by -1.72%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-11.1 mm
-1.72%
Speedometer at 100
98.3 km/h
-1.72% error
Ground clearance
-5.5 mm
ride height delta
Sidewall change
-18.3 mm
revs/km: 500.7
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/compare/215-50-r17-vs-255-35-r18Detailed comparison
| Metric | 215/50 R17 | 255/35 R18 | Difference |
|---|---|---|---|
| Overall diameter | 646.8 mm | 635.7 mm | -11.1 mm (-1.72%) |
| Sidewall height | 107.5 mm | 89.3 mm | -18.3 mm |
| Circumference | 2.032 m | 1.997 m | -34.9 mm |
| Revs / km | 492.1 | 500.7 | +8.6 |
| Ground clearance | reference | -5.5 mm | -5.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 98.3 km/h | -1.72 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 98.3 km/h after switching to 255/35 R18 — a -1.72% 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 -5.5 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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215/50 R17
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255/35 R18
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