275/40 R20 vs 255/55 R18
275/40 R20 vs 255/55 R18
255/55 R18 stays within the configured tolerance for 275/40 R20: +1.3% diameter and +1.3% speedometer effect.
Fitment verdict
255/55 R18 stays within the configured tolerance for 275/40 R20: +1.3% diameter and +1.3% speedometer effect.
| Metric | This size: 275/40 R20 | Alternative: 255/55 R18 | Difference | Verdict |
|---|---|---|---|---|
| Overall diameter | 28.66 in | 29.04 in | +1.3% | Within tolerance |
| Section width | 10.83 in | 10.04 in | -0.79 in | Computed difference |
| Sidewall height | 4.33 in | 5.52 in | +1.19 in | Computed difference |
| Circumference | 90.04 in | 91.24 in | +1.3% | Within tolerance |
| Speedo | 0.0% | +1.3% | +1.3% | Within tolerance |
Compare sizes
Looks valid
Looks valid
Units
✓ Within toleranceDiameter +1.3% (+0.38 in) · US (~3%)
- Within tolerance · Diameter +1.3%.
- Speedo @ 60: 60 mph → 60.8 mph.
- Sidewall +1.19 in · Width -0.79 in.
Diameter+1.3%+0.38 in
Speedo @ 60+1.3%60 mph → 60.8 mph
Sidewall+1.19 inWidth -0.79 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
- 28.66 in 29.04 in+0.38 in
- Sidewall
- 4.33 in 5.52 in+1.19 in
- Width
- 10.83 in 10.04 in-0.79 in
- Circumference
- 90.04 in 91.24 in+1.3%
- Revs / mile
- 704 694
- Speedo @ 60
- 60 mph 60.8 mph+1.3%
- Current —
275/40 R20 - New —
255/55 R18 - Grounded to the road: the axle rises +0.19 in.
Result report
275/40 R20 255/55 R18 · Within tolerance
Use this size when shopping: 255/55 R18
Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.
Safe alternative sizes
| Size | Diameter | Speedo @ 100 | Use this |
|---|---|---|---|
−1″ 175/70R19 | -0.1% | -0.1% | |
OE 275/40R20 | +0.0% | +0.0% | |
+1″ 195/50R21 | +0.1% | +0.1% | |
+2″ 155/55R22 | +0.2% | +0.2% |
275/40 R20 · 255/55 R18 · Methodology
What changed
- Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.