Comparison
235/50 R18 vs 245/45 R18
245/45 R18 is a wider variation of 235/50 R18 on the same 18-inch rim, adding 10 mm of tread footprint. This setup shifts overall diameter slightly from OEM.
The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeUseful when extra dry grip and stance matter more than a small fuel-economy hit.
Quick math: 245/45 R18 is 14.5 mm shorter than 235/50 R18, shifting the speedometer by -2.09%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-14.5 mm
-2.09%
Speedometer at 100
97.9 km/h
-2.09% error
Ground clearance
-7.3 mm
ride height delta
Sidewall change
-7.3 mm
revs/km: 469.7
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/compare/235-50-r18-vs-245-45-r18Detailed comparison
| Metric | 235/50 R18 | 245/45 R18 | Difference |
|---|---|---|---|
| Overall diameter | 692.2 mm | 677.7 mm | -14.5 mm (-2.09%) |
| Sidewall height | 117.5 mm | 110.3 mm | -7.3 mm |
| Circumference | 2.175 m | 2.129 m | -45.6 mm |
| Revs / km | 459.9 | 469.7 | +9.8 |
| Ground clearance | reference | -7.3 mm | -7.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.9 km/h | -2.09 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 97.9 km/h after switching to 245/45 R18 — a -2.09% 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 -7.3 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.
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235/50 R18
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245/45 R18
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