Comparison
215/50 R17 vs 245/45 R18
Plus-sizing from 215/50 R17 to 245/45 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.
Indicated speed will drift far enough that recalibration is worth considering. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. Many drivers pick this direction primarily for appearance — the bigger rim simply looks more aggressive. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 245/45 R18 is 30.9 mm taller than 215/50 R17, shifting the speedometer by +4.78%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+30.9 mm
4.78%
Speedometer at 100
104.8 km/h
+4.78% error
Ground clearance
+15.5 mm
ride height delta
Sidewall change
+2.8 mm
revs/km: 469.7
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/compare/215-50-r17-vs-245-45-r18Detailed comparison
| Metric | 215/50 R17 | 245/45 R18 | Difference |
|---|---|---|---|
| Overall diameter | 646.8 mm | 677.7 mm | +30.9 mm (+4.78%) |
| Sidewall height | 107.5 mm | 110.3 mm | +2.8 mm |
| Circumference | 2.032 m | 2.129 m | +97.1 mm |
| Revs / km | 492.1 | 469.7 | -22.4 |
| Ground clearance | reference | +15.5 mm | +15.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 104.8 km/h | +4.78 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 104.8 km/h after switching to 245/45 R18 — a +4.78% 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 +15.5 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.
Back to
215/50 R17
Back to
245/45 R18
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