245/45 R18 vs 255/40 R19
245/45 R18 vs 255/40 R19
255/40 R19 stays within the configured tolerance for 245/45 R18: +1.3% diameter and +1.3% speedometer effect.
Fitment verdict
255/40 R19 stays within the configured tolerance for 245/45 R18: +1.3% diameter and +1.3% speedometer effect.
| Metric | This size: 245/45 R18 | Alternative: 255/40 R19 | Difference | Verdict |
|---|---|---|---|---|
| Overall diameter | 26.68 in | 27.03 in | +1.3% | Within tolerance |
| Section width | 9.65 in | 10.04 in | +0.39 in | Computed difference |
| Sidewall height | 4.34 in | 4.02 in | -0.32 in | Computed difference |
| Circumference | 83.82 in | 84.92 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% (+0.35 in) · US (~3%)
- Within tolerance · Diameter +1.3%.
- Speedo @ 60: 60 mph → 60.8 mph.
- Sidewall -0.32 in · Width +0.39 in.
Diameter+1.3%+0.35 in
Speedo @ 60+1.3%60 mph → 60.8 mph
Sidewall-0.32 inWidth +0.39 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
- 26.68 in 27.03 in+0.35 in
- Sidewall
- 4.34 in 4.02 in-0.32 in
- Width
- 9.65 in 10.04 in+0.39 in
- Circumference
- 83.82 in 84.92 in+1.3%
- Revs / mile
- 756 746
- Speedo @ 60
- 60 mph 60.8 mph+1.3%
- Current —
245/45 R18 - New —
255/40 R19 - Grounded to the road: the axle rises +0.18 in.
Result report
245/45 R18 255/40 R19 · Within tolerance
Use this size when shopping: 255/40 R19
Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.
Safe alternative sizes
| Size | Diameter | Speedo @ 100 | Use this |
|---|---|---|---|
−1″ 205/60R17 | +0.0% | +0.0% | |
OE 245/45R18 | +0.0% | +0.0% | |
+1″ 195/50R19 | -0.0% | -0.0% | |
+2″ 155/55R20 | +0.1% | +0.1% |
245/45 R18 · 255/40 R19 · Methodology
What changed
- Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.