275/70 R18 vs 35x12.50 R20

35x12.50 R20 is outside the configured tolerance for 275/70 R18: +5.6% diameter and +5.6% speedometer effect.

Geometric comparison

35x12.50 R20 is outside the configured tolerance for 275/70 R18: +5.6% diameter and +5.6% speedometer effect.

Geometric comparison
Metric	This size: 275/70 R18	Alternative: 35x12.50 R20	Difference	Verdict
Overall diameter	33.16 in	35.00 in	+5.6%	Too tall
Section width	10.83 in	12.50 in	+1.67 in	Computed difference
Sidewall height	7.58 in	7.50 in	-0.08 in	Computed difference
Circumference	104.17 in	109.96 in	+5.6%	Too tall
Speedo	0.0%	+5.6%	+5.6%	Outside tolerance

Compare sizes

Current tireLooks valid

New tireLooks valid

Market

Units

High fitment riskOut of tolerance · Diameter +5.6% (+1.84 in) · US (~3%)

High fitment risk · This rating covers tire geometry only, not vehicle compatibility.
Diameter +5.6% · Ride-height change +0.92 in.
Speedometer reads low · 60 mph → 63.3 mph.
Sidewall -0.08 in · Width +1.67 in.

Diameter+5.6%+1.84 in

Speedo @ 60+5.6%60 mph → 63.3 mph

Sidewall-0.08 inWidth +1.67 in

Ride-height change+0.92 inDiameter ÷ 2

How this result is calculated

Computed from nominal tire-size geometry: diameter, circumference and speedometer error. It does not check vehicle placard approval, load/speed rating, rim-width range, wheel-arch, suspension or brake clearance.

Methodology

Before fitting

Check the vehicle placard and owner’s manual first.
Match or exceed the required load index and speed rating.
Confirm rim-width range, bolt pattern, hub bore, offset and fasteners.
Inspect wheel-arch, suspension and brake clearance under real vehicle load.
Check TPMS, cold pressure and local roadworthiness rules.

Diameter: 33.16 in 35.00 in+1.84 in
Sidewall: 7.58 in 7.50 in-0.08 in
Width: 10.83 in 12.50 in+1.67 in
Circumference: 104.17 in 109.96 in+5.6%
Revs / mile: 608 576
Speedo @ 60: 60 mph 63.3 mph+5.6%
Ride-height change: 0.00 in +0.92 in
True distance per 100 indicated: 100 mi 105.6 mi+5.6%

Current — 275/70 R18
New — 35x12.50 R20
Grounded to the road: the axle rises +0.92 in.

Result report

275/70 R18 35x12.50 R20 · High fitment risk · Out of tolerance

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Markdown link

[275/70 R18 vs 35x12.50 R20 Tire size comparison](https://tirefitlab.com/tire-size-calculator/?from=275%2F70+R18&to=35x12.50+R20&market=us)

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Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.

In-tolerance alternative sizes

In-tolerance alternative sizes
Size	Diameter	Speedo @ 100	Use this
OE `275/70R18`	+0.0%	+0.0%

275/70 R18 · 35x12.50 R20 · Methodology

Technical check: 2026-06-28

What changed

Checked generated routes, metadata, sitemap inclusion and localized page rendering.

Methodology