Comparison
225/45 R18 vs 235/40 R18
On the same 18-inch wheel, 235/40 R18 grows the section width by 10 mm versus 225/45 R18. This alternative fitment shifts overall diameter slightly from OEM. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input.
Expect a slight but noticeable shift in indicated speed compared to the original tires. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeUseful when extra dry grip and stance matter more than a small fuel-economy hit.
Quick math: 235/40 R18 is 14.5 mm shorter than 225/45 R18, shifting the speedometer by -2.20%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-14.5 mm
-2.20%
Speedometer at 100
97.8 km/h
-2.20% error
Ground clearance
-7.3 mm
ride height delta
Sidewall change
-7.3 mm
revs/km: 493.4
Permalink for this comparison:
/compare/225-45-r18-vs-235-40-r18Detailed comparison
| Metric | 225/45 R18 | 235/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 659.7 mm | 645.2 mm | -14.5 mm (-2.20%) |
| Sidewall height | 101.3 mm | 94.0 mm | -7.3 mm |
| Circumference | 2.073 m | 2.027 m | -45.6 mm |
| Revs / km | 482.5 | 493.4 | +10.8 |
| Ground clearance | reference | -7.3 mm | -7.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.8 km/h | -2.20 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 97.8 km/h after switching to 235/40 R18 — a -2.20% 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.
Back to
225/45 R18
Back to
235/40 R18
Drivers also compare
Closely-related fitments and plus-size swaps for 225/45 R18 and 235/40 R18.
225/45 R18 vs 255/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.23%
235/40 R18 vs 275/35 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.70%
215/45 R18 vs 235/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.85%
225/45 R18 vs 245/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.99%
235/40 R18 vs 245/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.24%
225/40 R18 vs 235/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.26%
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