255/50 R20

What size is 255/50 R20?

255/50 R20 has an overall diameter of about 30.04 in, a section width of 10.04 in and a sidewall height of 5.02 in. It turns roughly 671 times per mile. Below are the exact figures plus plus/minus sizes that stay within the selected diameter tolerance.

Geometric comparison

255/65 R17 stays within the configured tolerance for 255/50 R20: 0.0% diameter and 0.0% speedometer effect.

Geometric comparison
Metric This size: 255/50 R20 Alternative: 255/65 R17 Difference Verdict
Overall diameter 30.04 in 30.05 in 0.0% Within tolerance
Section width 10.04 in 10.04 in 0.00 in Computed difference
Sidewall height 5.02 in 6.53 in +1.51 in Computed difference
Circumference 94.37 in 94.41 in 0.0% Within tolerance
Speedo 0.0% 0.0% 0.0% Within tolerance

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What this geometry means

255/50 R20 has a mid-range sidewall proportion. The marking combines nominal section width 10.04 in, sidewall ratio 50% and rim diameter 20 inches. One sidewall is 5.02 in; both sidewalls make up 33% of the 30.04 in overall diameter, while the rim makes up 67%.

At the nominal 94.37 in circumference, 1,000 rotations cover 2.40 km (1.49 mi); the inverse rates are 417/km and 671/mi.

Section-width mix versus 255/50 R20: 4 narrower, 1 equal-width and 7 wider entries.

The closest diameter entry is 255/65 R17 at +0.0%. Relative to 255/50 R20, it changes nominal section width by +0.00 in, each sidewall by +1.51 in and radius by +0.01 in.

Curated alternatives: 12 sizes, spanning -1.5% to +1.6% in nominal diameter versus 255/50 R20.

Width endpoints in that set are 235/65 R18 (-0.79 in) and 305/40 R20 (+1.97 in) relative to 255/50 R20.

This is a nominal geometry comparison only. Vehicle clearance, wheel width and offset, load and speed ratings, and manufacturer approval still require separate checks.

Specification

Specification
Overall diameter 30.04 in
Section width 10.04 in
Sidewall height 5.02 in
Circumference 94.37 in
Revolutions 417 /km · 671 /mi

In-tolerance sizes

Alternative sizes that stay within the selected diameter tolerance:

In-tolerance sizes
Size Diameter Speedo Verdict
255/65 R17 +0.0% +0.0% ✓ OK
235/65 R18 -0.0% -0.0% ✓ OK
235/70 R17 -0.3% -0.3% ✓ OK
285/35 R22 -0.6% -0.6% ✓ OK
275/45 R20 -1.0% -1.0% ✓ OK
265/40 R22 +1.0% +1.0% ✓ OK
265/45 R21 +1.2% +1.2% ✓ OK
265/50 R20 +1.3% +1.3% ✓ OK
305/40 R20 -1.4% -1.4% ✓ OK
245/70 R17 +1.5% +1.5% ✓ OK
245/60 R18 -1.5% -1.5% ✓ OK
265/60 R18 +1.6% +1.6% ✓ OK

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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.

High fitment riskWithin tolerance · Diameter +0.0% (+0.01 in) · US preset (±3%)
  • High fitment risk · This rating covers tire geometry only, not vehicle compatibility.
  • Diameter +0.0% · Ride-height change +0.01 in.
  • Speedometer unchanged · 60 mph → 60.0 mph.
  • Sidewall +1.51 in · Width +0.00 in.
Diameter+0.0%+0.01 in
Speedo @ 60+0.0%60 mph → 60.0 mph
Sidewall+1.51 inWidth +0.00 in
Ride-height change+0.01 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
30.04 in 30.05 in+0.01 in
Sidewall
5.02 in 6.53 in+1.51 in
Width
10.04 in 10.04 in+0.00 in
Circumference
94.37 in 94.41 in+0.0%
Revs / mile
671 671
Speedo @ 60
60 mph 60.0 mph+0.0%
Ride-height change
0.00 in +0.01 in
True distance per 100 indicated
100 mi 100.0 mi+0.0%
Δ⌀ +0.01 inΔ↔ +0.00 in
  • Current — 255/50 R20
  • New — 255/65 R17
  • Grounded to the road: the axle rises +0.01 in.

Tires and wheels in one comparison

Result report

255/50 R20 255/65 R17 · High fitment risk · Within 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″ 245/55R19-1.4%-1.4%
OE 255/50R20+0.0%+0.0%
+1″ 265/45R21+1.2%+1.2%
+2″ 265/40R22+1.0%+1.0%

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Last reviewed: 2026-09-04