Comparison
235/45 R18 vs 245/45 R17
Going from 235/45 R18 to 245/45 R17 is a minus-1 setup that adds sidewall on a smaller 17-inch wheel. This wheel and tire pairing shifts overall diameter slightly from OEM. The wider section adds contact patch and lateral stability, while eating into fender and suspension clearance.
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.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 245/45 R17 is 16.4 mm shorter than 235/45 R18, shifting the speedometer by -2.45%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-16.4 mm
-2.45%
Speedometer at 100
97.5 km/h
-2.45% error
Ground clearance
-8.2 mm
ride height delta
Sidewall change
+4.5 mm
revs/km: 488.0
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/compare/235-45-r18-vs-245-45-r17Detailed comparison
| Metric | 235/45 R18 | 245/45 R17 | Difference |
|---|---|---|---|
| Overall diameter | 668.7 mm | 652.3 mm | -16.4 mm (-2.45%) |
| Sidewall height | 105.8 mm | 110.3 mm | +4.5 mm |
| Circumference | 2.101 m | 2.049 m | -51.5 mm |
| Revs / km | 476.0 | 488.0 | +12.0 |
| Ground clearance | reference | -8.2 mm | -8.2 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.5 km/h | -2.45 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 97.5 km/h after switching to 245/45 R17 — a -2.45% 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 -8.2 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.
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235/45 R18
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245/45 R17
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