Comparison
225/45 R18 vs 275/40 R18
Stepping from 225/45 R18 to 275/40 R18 keeps the 18-inch wheel but widens the section by 50 mm. This setup trims or stretches rolling diameter by a small margin. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement.
The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeReasonable performance-leaning swap as long as fender and suspension clearance check out.
Quick math: 275/40 R18 is 17.5 mm taller than 225/45 R18, shifting the speedometer by +2.65%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+17.5 mm
2.65%
Speedometer at 100
102.7 km/h
+2.65% error
Ground clearance
+8.8 mm
ride height delta
Sidewall change
+8.8 mm
revs/km: 470.0
Permalink for this comparison:
/compare/225-45-r18-vs-275-40-r18Detailed comparison
| Metric | 225/45 R18 | 275/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 659.7 mm | 677.2 mm | +17.5 mm (+2.65%) |
| Sidewall height | 101.3 mm | 110.0 mm | +8.8 mm |
| Circumference | 2.073 m | 2.127 m | +55.0 mm |
| Revs / km | 482.5 | 470.0 | -12.5 |
| Ground clearance | reference | +8.8 mm | +8.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.7 km/h | +2.65 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 102.7 km/h after switching to 275/40 R18 — a +2.65% 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 +8.8 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.
Back to
225/45 R18
Back to
275/40 R18
Drivers also compare
Closely-related fitments and plus-size swaps for 225/45 R18 and 275/40 R18.
245/45 R18 vs 275/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.07%
225/45 R18 vs 255/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.23%
225/50 R18 vs 275/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.73%
225/45 R18 vs 245/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.99%
265/40 R18 vs 275/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.20%
235/45 R18 vs 275/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.27%
225/45 R18 vs 235/45 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.36%
215/45 R18 vs 225/45 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.38%
Related topics