TireFitLab

275/55 R20 vs 35x12.50 R18

275/55 R20 vs 35x12.50 R18

35x12.50 R18 is outside the configured tolerance for 275/55 R20: +9.7% diameter and +9.7% speedometer effect.

Fitment verdict

35x12.50 R18 is outside the configured tolerance for 275/55 R20: +9.7% diameter and +9.7% speedometer effect.

Metric This size: 275/55 R20 Alternative: 35x12.50 R18 Difference Verdict
Overall diameter 31.91 in 35.00 in +9.7% Too tall
Section width 10.83 in 12.50 in +1.67 in Computed difference
Sidewall height 5.95 in 8.50 in +2.55 in Computed difference
Circumference 100.25 in 109.96 in +9.7% Too tall
Speedo 0.0% +9.7% +9.7% Outside tolerance

Compare sizes

Looks valid
Looks valid
Units
✕ Out of toleranceDiameter +9.7% (+3.09 in) · US (~3%)
  • Out of tolerance · Diameter +9.7%.
  • Speedo @ 60: 60 mph → 65.8 mph.
  • Sidewall +2.55 in · Width +1.67 in.
Diameter+9.7%+3.09 in
Speedo @ 60+9.7%60 mph → 65.8 mph
Sidewall+2.55 inWidth +1.67 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
31.91 in 35.00 in+3.09 in
Sidewall
5.95 in 8.50 in+2.55 in
Width
10.83 in 12.50 in+1.67 in
Circumference
100.25 in 109.96 in+9.7%
Revs / mile
632 576
Speedo @ 60
60 mph 65.8 mph+9.7%
Δ⌀ +78.5 mm
  • Current — 275/55 R20
  • New — 35x12.50 R18
  • Grounded to the road: the axle rises +1.55 in.

Result report

275/55 R20 35x12.50 R18 · Out of tolerance

Use this size when shopping: 35x12.50 R18

Use this size when shopping

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

Safe alternative sizes

SizeDiameterSpeedo @ 100Use this
−1″ 205/80R19+0.0%+0.0%
OE 275/55R20+0.0%+0.0%
+1″ 185/75R21+0.0%+0.0%
+2″ 315/40R22+0.0%+0.0%

275/55 R20 · 35x12.50 R18 · Methodology

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