31x10.50 R15 vs 275/70 R18

What changes when you change tire size?

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

Geometric comparison

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

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Looks valid
Looks valid
Units
Editorial preset

These are TireFitLab editorial diameter-screening presets. Regional names choose a preset, not a national legal limit, ETRTO rule or vehicle approval. The AWD preset does not establish an allowable drivetrain mismatch. Use the exact vehicle and tyre manufacturer instructions; nominal geometry alone cannot approve fitment.

Not recommendedOut of tolerance · Diameter +7.0% (+2.16 in) · US preset (±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%
Δ⌀ +2.16 inΔ↔ +0.33 in
  • Current — 31x10.50 R15
  • New — 275/70 R18
  • Grounded to the road: the axle rises +1.08 in.

Tires and wheels in one comparison

Result report

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

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

In-tolerance alternative sizes

In-tolerance alternative sizes
SizeDiameterSpeedo @ 100Use this
−1″ 265/80R14-1.0%-1.0%
OE 265/75R15-1.1%-1.1%
+1″ 275/70R16+0.5%+0.5%
+2″ 265/70R17+2.0%+2.0%

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