31x10.50 R15 vs 275/70 R18

275/70 R18 is outside the configured tolerance for 31x10.50 R15: +7.0% diameter and +7.0% speedometer effect.

Geometric comparison

275/70 R18 is outside the configured tolerance for 31x10.50 R15: +7.0% diameter and +7.0% speedometer effect.

Geometric comparison
Metric	This size: 31x10.50 R15	Alternative: 275/70 R18	Difference	Verdict
Overall diameter	31.00 in	33.16 in	+7.0%	Too tall
Section width	10.50 in	10.83 in	+0.33 in	Computed difference
Sidewall height	8.00 in	7.58 in	-0.42 in	Computed difference
Circumference	97.39 in	104.17 in	+7.0%	Too tall
Speedo	0.0%	+7.0%	+7.0%	Outside tolerance

Compare sizes

Current tireLooks valid

New tireLooks valid

Market

Units

Not recommendedOut of tolerance · Diameter +7.0% (+2.16 in) · US (~3%)

Not recommended · This rating covers tire geometry only, not vehicle compatibility.
Diameter +7.0% · Ride-height change +1.08 in.
Speedometer reads low · 60 mph → 64.2 mph.
Sidewall -0.42 in · Width +0.33 in.

Diameter+7.0%+2.16 in

Speedo @ 60+7.0%60 mph → 64.2 mph

Sidewall-0.42 inWidth +0.33 in

Ride-height change+1.08 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: 31.00 in 33.16 in+2.16 in
Sidewall: 8.00 in 7.58 in-0.42 in
Width: 10.50 in 10.83 in+0.33 in
Circumference: 97.39 in 104.17 in+7.0%
Revs / mile: 651 608
Speedo @ 60: 60 mph 64.2 mph+7.0%
Ride-height change: 0.00 in +1.08 in
True distance per 100 indicated: 100 mi 107.0 mi+7.0%

Current — 31x10.50 R15
New — 275/70 R18
Grounded to the road: the axle rises +1.08 in.

Result report

31x10.50 R15 275/70 R18 · Not recommended · Out of tolerance

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Markdown link

[31x10.50 R15 vs 275/70 R18 Tire size comparison](https://tirefitlab.com/tire-size-calculator/?from=31x10.50+R15&to=275%2F70+R18&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 `255/80R15`	+0.2%	+0.2%

31x10.50 R15 · 275/70 R18 · Methodology

Technical check: 2026-06-28

What changed

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

Methodology