Comparison
245/35 R18 vs 245/45 R17
Switching from 245/35 R18 to 245/45 R17 steps down to a 17-inch wheel — a familiar move for winter and dedicated all-terrain sets. This setup noticeably changes overall diameter compared to OEM. Extra sidewall absorbs impacts more readily — a sensible bias for daily commuting and broken pavement.
The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 245/45 R17 is 23.6 mm taller than 245/35 R18, shifting the speedometer by +3.75%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+23.6 mm
3.75%
Speedometer at 100
103.8 km/h
+3.75% error
Ground clearance
+11.8 mm
ride height delta
Sidewall change
+24.5 mm
revs/km: 488.0
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/compare/245-35-r18-vs-245-45-r17Detailed comparison
| Metric | 245/35 R18 | 245/45 R17 | Difference |
|---|---|---|---|
| Overall diameter | 628.7 mm | 652.3 mm | +23.6 mm (+3.75%) |
| Sidewall height | 85.8 mm | 110.3 mm | +24.5 mm |
| Circumference | 1.975 m | 2.049 m | +74.1 mm |
| Revs / km | 506.3 | 488.0 | -18.3 |
| Ground clearance | reference | +11.8 mm | +11.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.8 km/h | +3.75 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 103.8 km/h after switching to 245/45 R17 — a +3.75% 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 +11.8 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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245/35 R18
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245/45 R17
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