Comparison
225/45 R17 vs 245/40 R18
Going from 225/45 R17 to 245/40 R18 steps up to a 18-inch rim while trimming sidewall to stay near OEM rolling diameter. This sizing approach shifts overall diameter slightly from OEM.
Expect a slight but noticeable shift in indicated speed compared to the original tires. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides. The wider section adds contact patch and lateral stability, while eating into fender and suspension clearance. Visually, the bigger wheel fills the arch and gives the car a more aggressive stance. 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: 245/40 R18 is 18.9 mm taller than 225/45 R17, shifting the speedometer by +2.98%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+18.9 mm
2.98%
Speedometer at 100
103.0 km/h
+2.98% error
Ground clearance
+9.5 mm
ride height delta
Sidewall change
-3.3 mm
revs/km: 487.3
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/compare/225-45-r17-vs-245-40-r18Detailed comparison
| Metric | 225/45 R17 | 245/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 634.3 mm | 653.2 mm | +18.9 mm (+2.98%) |
| Sidewall height | 101.3 mm | 98.0 mm | -3.3 mm |
| Circumference | 1.993 m | 2.052 m | +59.4 mm |
| Revs / km | 501.8 | 487.3 | -14.5 |
| Ground clearance | reference | +9.5 mm | +9.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.0 km/h | +2.98 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 103.0 km/h after switching to 245/40 R18 — a +2.98% 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 +9.5 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
225/45 R17
Back to
245/40 R18
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