Comparison
235/45 R17 vs 245/40 R17
On the same 17-inch wheel, 245/40 R17 grows the section width by 10 mm versus 235/45 R17. This alternative fitment 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. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeReasonable performance-leaning swap as long as fender and suspension clearance check out.
Quick math: 245/40 R17 is 15.5 mm shorter than 235/45 R17, shifting the speedometer by -2.41%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-15.5 mm
-2.41%
Speedometer at 100
97.6 km/h
-2.41% error
Ground clearance
-7.8 mm
ride height delta
Sidewall change
-7.8 mm
revs/km: 507.0
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/compare/235-45-r17-vs-245-40-r17Detailed comparison
| Metric | 235/45 R17 | 245/40 R17 | Difference |
|---|---|---|---|
| Overall diameter | 643.3 mm | 627.8 mm | -15.5 mm (-2.41%) |
| Sidewall height | 105.8 mm | 98.0 mm | -7.8 mm |
| Circumference | 2.021 m | 1.972 m | -48.7 mm |
| Revs / km | 494.8 | 507.0 | +12.2 |
| Ground clearance | reference | -7.8 mm | -7.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.6 km/h | -2.41 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 97.6 km/h after switching to 245/40 R17 — a -2.41% 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 -7.8 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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235/45 R17
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245/40 R17
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