235/55 R18 vs 275/40 R20
235/55 R18 vs 275/40 R20
275/40 R20 stays within the configured tolerance for 235/55 R18: +1.7% diameter and +1.7% speedometer effect.
Fitment verdict
275/40 R20 stays within the configured tolerance for 235/55 R18: +1.7% diameter and +1.7% speedometer effect.
| Metric | This size: 235/55 R18 | Alternative: 275/40 R20 | Difference | Verdict |
|---|---|---|---|---|
| Overall diameter | 28.18 in | 28.66 in | +1.7% | Within tolerance |
| Section width | 9.25 in | 10.83 in | +1.57 in | Computed difference |
| Sidewall height | 5.09 in | 4.33 in | -0.76 in | Computed difference |
| Circumference | 88.52 in | 90.04 in | +1.7% | Within tolerance |
| Speedo | 0.0% | +1.7% | +1.7% | Within tolerance |
Compare sizes
Looks valid
Looks valid
Units
✓ Within toleranceDiameter +1.7% (+0.48 in) · US (~3%)
- Within tolerance · Diameter +1.7%.
- Speedo @ 60: 60 mph → 61.0 mph.
- Sidewall -0.76 in · Width +1.57 in.
Diameter+1.7%+0.48 in
Speedo @ 60+1.7%60 mph → 61.0 mph
Sidewall-0.76 inWidth +1.57 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
- 28.18 in 28.66 in+0.48 in
- Sidewall
- 5.09 in 4.33 in-0.76 in
- Width
- 9.25 in 10.83 in+1.57 in
- Circumference
- 88.52 in 90.04 in+1.7%
- Revs / mile
- 716 704
- Speedo @ 60
- 60 mph 61.0 mph+1.7%
- Current —
235/55 R18 - New —
275/40 R20 - Grounded to the road: the axle rises +0.24 in.
Result report
235/55 R18 275/40 R20 · Within tolerance
Use this size when shopping: 275/40 R20
Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.
Safe alternative sizes
| Size | Diameter | Speedo @ 100 | Use this |
|---|---|---|---|
−1″ 355/40R17 | +0.0% | +0.0% | |
OE 235/55R18 | +0.0% | +0.0% | |
+1″ 155/75R19 | -0.1% | -0.1% | |
+2″ 345/30R20 | -0.1% | -0.1% |
235/55 R18 · 275/40 R20 · Methodology
What changed
- Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.