TireFitLab

275/70 R18 vs 37x13.50 R20

275/70 R18 vs 37x13.50 R20

37x13.50 R20 is outside the configured tolerance for 275/70 R18: +11.6% diameter and +11.6% speedometer effect.

Fitment verdict

37x13.50 R20 is outside the configured tolerance for 275/70 R18: +11.6% diameter and +11.6% speedometer effect.

Metric This size: 275/70 R18 Alternative: 37x13.50 R20 Difference Verdict
Overall diameter 33.16 in 37.00 in +11.6% Too tall
Section width 10.83 in 13.50 in +2.67 in Computed difference
Sidewall height 7.58 in 8.50 in +0.92 in Computed difference
Circumference 104.17 in 116.24 in +11.6% Too tall
Speedo 0.0% +11.6% +11.6% Outside tolerance

Compare sizes

Looks valid
Looks valid
Units
✕ Out of toleranceDiameter +11.6% (+3.84 in) · US (~3%)
  • Out of tolerance · Diameter +11.6%.
  • Speedo @ 60: 60 mph → 67.0 mph.
  • Sidewall +0.92 in · Width +2.67 in.
Diameter+11.6%+3.84 in
Speedo @ 60+11.6%60 mph → 67.0 mph
Sidewall+0.92 inWidth +2.67 in
How this result is calculated

Computed from nominal tire-size geometry: diameter, circumference and speedometer error. It does not check wheel-arch, suspension or brake clearance.

Methodology
Diameter
33.16 in 37.00 in+3.84 in
Sidewall
7.58 in 8.50 in+0.92 in
Width
10.83 in 13.50 in+2.67 in
Circumference
104.17 in 116.24 in+11.6%
Revs / mile
608 545
Speedo @ 60
60 mph 67.0 mph+11.6%
Δ⌀ +97.6 mm
  • Current — 275/70 R18
  • New — 37x13.50 R20
  • Grounded to the road: the axle rises +1.92 in.

Result report

275/70 R18 37x13.50 R20 · Out of tolerance

Use this size when shopping: 37x13.50 R20

Use this size when shopping

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

Safe alternative sizes

SizeDiameterSpeedo @ 100Use this
−1″ 315/65R17-0.1%-0.1%
OE 275/70R18+0.0%+0.0%
+1″ 225/80R19+0.0%+0.0%
+2″ 335/50R20+0.1%+0.1%

275/70 R18 · 37x13.50 R20 · Methodology

Last reviewed: 2026-06-28
What changed
  • Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.