Comparison
245/35 R18 vs 245/40 R18
Going from 245/35 R18 to 245/40 R18 raises the aspect ratio by 5 points on the same 18-inch wheel. This tire combination swings rolling diameter far enough to feel on the road.
The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. Extra sidewall absorbs impacts more readily — a sensible bias for daily commuting and broken pavement. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeA comfort-leaning direction that's easier on wheels and suspension over rough surfaces.
Quick math: 245/40 R18 is 24.5 mm taller than 245/35 R18, shifting the speedometer by +3.90%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+24.5 mm
3.90%
Speedometer at 100
103.9 km/h
+3.90% error
Ground clearance
+12.3 mm
ride height delta
Sidewall change
+12.3 mm
revs/km: 487.3
Permalink for this comparison:
/compare/245-35-r18-vs-245-40-r18Detailed comparison
| Metric | 245/35 R18 | 245/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 628.7 mm | 653.2 mm | +24.5 mm (+3.90%) |
| Sidewall height | 85.8 mm | 98.0 mm | +12.3 mm |
| Circumference | 1.975 m | 2.052 m | +77.0 mm |
| Revs / km | 506.3 | 487.3 | -19.0 |
| Ground clearance | reference | +12.3 mm | +12.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.9 km/h | +3.90 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 103.9 km/h after switching to 245/40 R18 — a +3.90% 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 +12.3 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
245/35 R18
Back to
245/40 R18
Drivers also compare
Closely-related fitments and plus-size swaps for 245/35 R18 and 245/40 R18.
215/40 R18 vs 245/35 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.08%
215/45 R18 vs 245/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.38%
245/40 R18 vs 275/35 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.54%
225/45 R18 vs 245/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.99%
245/35 R18 vs 255/35 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.11%
245/40 R18 vs 255/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.22%
235/40 R18 vs 245/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.24%
225/40 R18 vs 245/35 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.33%
Related topics