Comparison
295/35 R20 vs 305/30 R20
On the same 20-inch wheel, 305/30 R20 grows the section width by 10 mm versus 295/35 R20. This sizing approach moves rolling diameter well outside the usual OEM tolerance. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeReasonable performance-leaning swap as long as fender and suspension clearance check out.
Quick math: 305/30 R20 is 23.5 mm shorter than 295/35 R20, shifting the speedometer by -3.29%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-23.5 mm
-3.29%
Speedometer at 100
96.7 km/h
-3.29% error
Ground clearance
-11.8 mm
ride height delta
Sidewall change
-11.8 mm
revs/km: 460.7
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/compare/295-35-r20-vs-305-30-r20Detailed comparison
| Metric | 295/35 R20 | 305/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 714.5 mm | 691.0 mm | -23.5 mm (-3.29%) |
| Sidewall height | 103.3 mm | 91.5 mm | -11.8 mm |
| Circumference | 2.245 m | 2.171 m | -73.8 mm |
| Revs / km | 445.5 | 460.7 | +15.2 |
| Ground clearance | reference | -11.8 mm | -11.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.7 km/h | -3.29 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 305/30 R20 — a -3.29% 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 -11.8 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.
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295/35 R20
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305/30 R20
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