Comparison
235/45 R17 vs 245/35 R18
Switching from 235/45 R17 to 245/35 R18 is a plus-1 upgrade that wraps a shorter sidewall around a larger 18-inch wheel. This sizing approach moves rolling diameter a touch off the original spec. The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 245/35 R18 is 14.6 mm shorter than 235/45 R17, shifting the speedometer by -2.27%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-14.6 mm
-2.27%
Speedometer at 100
97.7 km/h
-2.27% error
Ground clearance
-7.3 mm
ride height delta
Sidewall change
-20.0 mm
revs/km: 506.3
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/compare/235-45-r17-vs-245-35-r18Detailed comparison
| Metric | 235/45 R17 | 245/35 R18 | Difference |
|---|---|---|---|
| Overall diameter | 643.3 mm | 628.7 mm | -14.6 mm (-2.27%) |
| Sidewall height | 105.8 mm | 85.8 mm | -20.0 mm |
| Circumference | 2.021 m | 1.975 m | -45.9 mm |
| Revs / km | 494.8 | 506.3 | +11.5 |
| Ground clearance | reference | -7.3 mm | -7.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.7 km/h | -2.27 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 97.7 km/h after switching to 245/35 R18 — a -2.27% 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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235/45 R17
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245/35 R18
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