TireFitLab

275/65 R18 vs 37x13.50 R20

275/65 R18 vs 37x13.50 R20

37x13.50 R20 is outside the configured tolerance for 275/65 R18: +15.4% diameter and +15.4% speedometer effect.

Fitment verdict

37x13.50 R20 is outside the configured tolerance for 275/65 R18: +15.4% diameter and +15.4% speedometer effect.

Metric This size: 275/65 R18 Alternative: 37x13.50 R20 Difference Verdict
Overall diameter 32.07 in 37.00 in +15.4% Too tall
Section width 10.83 in 13.50 in +2.67 in Computed difference
Sidewall height 7.04 in 8.50 in +1.46 in Computed difference
Circumference 100.77 in 116.24 in +15.4% Too tall
Speedo 0.0% +15.4% +15.4% Outside tolerance

Compare sizes

Looks valid
Looks valid
Units
✕ Out of toleranceDiameter +15.4% (+4.93 in) · US (~3%)
  • Out of tolerance · Diameter +15.4%.
  • Speedo @ 60: 60 mph → 69.2 mph.
  • Sidewall +1.46 in · Width +2.67 in.
Diameter+15.4%+4.93 in
Speedo @ 60+15.4%60 mph → 69.2 mph
Sidewall+1.46 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
32.07 in 37.00 in+4.93 in
Sidewall
7.04 in 8.50 in+1.46 in
Width
10.83 in 13.50 in+2.67 in
Circumference
100.77 in 116.24 in+15.4%
Revs / mile
629 545
Speedo @ 60
60 mph 69.2 mph+15.4%
Δ⌀ +125.1 mm
  • Current — 275/65 R18
  • New — 37x13.50 R20
  • Grounded to the road: the axle rises +2.46 in.

Result report

275/65 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″ 255/75R17-0.0%-0.0%
OE 275/65R18+0.0%+0.0%
+1″ 255/65R19-0.1%-0.1%
+2″ 255/60R20-0.1%-0.1%

275/65 R18 · 37x13.50 R20 · Methodology

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