Comparison
235/45 R17 vs 265/40 R18
Switching from 235/45 R17 to 265/40 R18 is a plus-1 upgrade that wraps a shorter sidewall around a larger 18-inch wheel. This alternative fitment noticeably changes overall diameter compared to OEM.
Indicated speed will drift far enough that recalibration is worth considering. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. Many drivers pick this direction primarily for appearance — the bigger rim simply looks more aggressive. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 265/40 R18 is 25.9 mm taller than 235/45 R17, shifting the speedometer by +4.03%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+25.9 mm
4.03%
Speedometer at 100
104.0 km/h
+4.03% error
Ground clearance
+13.0 mm
ride height delta
Sidewall change
+0.3 mm
revs/km: 475.7
Permalink for this comparison:
/compare/235-45-r17-vs-265-40-r18Detailed comparison
| Metric | 235/45 R17 | 265/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 643.3 mm | 669.2 mm | +25.9 mm (+4.03%) |
| Sidewall height | 105.8 mm | 106.0 mm | +0.3 mm |
| Circumference | 2.021 m | 2.102 m | +81.4 mm |
| Revs / km | 494.8 | 475.7 | -19.2 |
| Ground clearance | reference | +13.0 mm | +13.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 104.0 km/h | +4.03 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 104.0 km/h after switching to 265/40 R18 — a +4.03% 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 +13.0 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
235/45 R17
Back to
265/40 R18
Drivers also compare
Closely-related fitments and plus-size swaps for 235/45 R17 and 265/40 R18.
235/45 R18 vs 265/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.07%
215/50 R17 vs 235/45 R17
Wider variation on the same rim — more grip, less clearance.
Δ 0.54%
205/50 R17 vs 235/45 R17
Wider variation on the same rim — more grip, less clearance.
Δ 1.02%
235/45 R17 vs 255/40 R17
Wider variation on the same rim — more grip, less clearance.
Δ 1.17%
265/40 R18 vs 275/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.20%
255/40 R18 vs 265/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.21%
245/45 R18 vs 265/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.25%
235/45 R17 vs 245/45 R17
Wider variation on the same rim — more grip, less clearance.
Δ 1.40%
Related topics