Comparison
275/35 R20 vs 275/40 R18
275/40 R18 drops the rim from 20 to 18 inches versus 275/35 R20, trading wheel size for taller sidewall. This tire combination moves rolling diameter well outside the usual OEM tolerance. More sidewall typically improves comfort and curb protection, especially on city streets.
Indicated speed will drift far enough that recalibration is worth considering. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 275/40 R18 is 23.3 mm shorter than 275/35 R20, shifting the speedometer by -3.33%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-23.3 mm
-3.33%
Speedometer at 100
96.7 km/h
-3.33% error
Ground clearance
-11.6 mm
ride height delta
Sidewall change
+13.8 mm
revs/km: 470.0
Permalink for this comparison:
/compare/275-35-r20-vs-275-40-r18Detailed comparison
| Metric | 275/35 R20 | 275/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 700.5 mm | 677.2 mm | -23.3 mm (-3.33%) |
| Sidewall height | 96.3 mm | 110.0 mm | +13.8 mm |
| Circumference | 2.201 m | 2.127 m | -73.2 mm |
| Revs / km | 454.4 | 470.0 | +15.6 |
| Ground clearance | reference | -11.6 mm | -11.6 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.7 km/h | -3.33 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 96.7 km/h after switching to 275/40 R18 — a -3.33% 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 -11.6 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
275/35 R20
Back to
275/40 R18
Drivers also compare
Closely-related fitments and plus-size swaps for 275/35 R20 and 275/40 R18.
245/45 R18 vs 275/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.07%
245/40 R20 vs 275/35 R20
Wider variation on the same rim — more grip, less clearance.
Δ 0.50%
225/50 R18 vs 275/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.73%
275/35 R20 vs 285/35 R20
Wider variation on the same rim — more grip, less clearance.
Δ 1.00%
265/35 R20 vs 275/35 R20
Wider variation on the same rim — more grip, less clearance.
Δ 1.01%
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%
275/35 R20 vs 305/30 R20
Wider variation on the same rim — more grip, less clearance.
Δ 1.36%
Related topics