Comparison
265/40 R20 vs 305/30 R20
Going from 265/40 R20 to 305/30 R20 keeps the rim but tightens the sidewall for a sportier look. This setup swings rolling diameter far enough to feel on the road. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement.
The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeSuits drivers who value sharper steering and appearance over outright ride softness.
Quick math: 305/30 R20 is 29.0 mm shorter than 265/40 R20, shifting the speedometer by -4.03%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-29.0 mm
-4.03%
Speedometer at 100
96.0 km/h
-4.03% error
Ground clearance
-14.5 mm
ride height delta
Sidewall change
-14.5 mm
revs/km: 460.7
Permalink for this comparison:
/compare/265-40-r20-vs-305-30-r20Detailed comparison
| Metric | 265/40 R20 | 305/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 720.0 mm | 691.0 mm | -29.0 mm (-4.03%) |
| Sidewall height | 106.0 mm | 91.5 mm | -14.5 mm |
| Circumference | 2.262 m | 2.171 m | -91.1 mm |
| Revs / km | 442.1 | 460.7 | +18.6 |
| Ground clearance | reference | -14.5 mm | -14.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.0 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 96.0 km/h after switching to 305/30 R20 — 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 -14.5 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
265/40 R20
Back to
305/30 R20
Drivers also compare
Closely-related fitments and plus-size swaps for 265/40 R20 and 305/30 R20.
265/35 R20 vs 305/30 R20
Wider variation on the same rim — more grip, less clearance.
Δ 0.36%
255/35 R20 vs 305/30 R20
Wider variation on the same rim — more grip, less clearance.
Δ 0.66%
265/40 R20 vs 295/35 R20
Wider variation on the same rim — more grip, less clearance.
Δ 0.76%
265/40 R20 vs 275/40 R20
Wider variation on the same rim — more grip, less clearance.
Δ 1.11%
245/45 R20 vs 265/40 R20
Wider variation on the same rim — more grip, less clearance.
Δ 1.17%
275/35 R20 vs 305/30 R20
Wider variation on the same rim — more grip, less clearance.
Δ 1.36%
245/35 R20 vs 305/30 R20
Wider variation on the same rim — more grip, less clearance.
Δ 1.69%
265/40 R20 vs 285/35 R20
Wider variation on the same rim — more grip, less clearance.
Δ 1.74%
Related topics