235/40 R18 vs 245/45 R17
235/40 R18 vs 245/45 R17
245/45 R17 stays within the configured tolerance for 235/40 R18: +1.1% diameter and +1.1% speedometer effect.
Fitment verdict
245/45 R17 stays within the configured tolerance for 235/40 R18: +1.1% diameter and +1.1% speedometer effect.
| Metric | This size: 235/40 R18 | Alternative: 245/45 R17 | Difference | Verdict |
|---|---|---|---|---|
| Overall diameter | 25.40 in | 25.68 in | +1.1% | Within tolerance |
| Section width | 9.25 in | 9.65 in | +0.39 in | Computed difference |
| Sidewall height | 3.70 in | 4.34 in | +0.64 in | Computed difference |
| Circumference | 79.80 in | 80.68 in | +1.1% | Within tolerance |
| Speedo | 0.0% | +1.1% | +1.1% | Within tolerance |
Compare sizes
Looks valid
Looks valid
Units
✓ Within toleranceDiameter +1.1% (+0.28 in) · US (~3%)
- Within tolerance · Diameter +1.1%.
- Speedo @ 60: 60 mph → 60.7 mph.
- Sidewall +0.64 in · Width +0.39 in.
Diameter+1.1%+0.28 in
Speedo @ 60+1.1%60 mph → 60.7 mph
Sidewall+0.64 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
- 25.40 in 25.68 in+0.28 in
- Sidewall
- 3.70 in 4.34 in+0.64 in
- Width
- 9.25 in 9.65 in+0.39 in
- Circumference
- 79.80 in 80.68 in+1.1%
- Revs / mile
- 794 785
- Speedo @ 60
- 60 mph 60.7 mph+1.1%
- Current —
235/40 R18 - New —
245/45 R17 - Grounded to the road: the axle rises +0.14 in.
Result report
235/40 R18 245/45 R17 · Within tolerance
Use this size when shopping: 245/45 R17
Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.
Safe alternative sizes
| Size | Diameter | Speedo @ 100 | Use this |
|---|---|---|---|
−1″ 305/35R17 | +0.0% | +0.0% | |
OE 235/40R18 | +0.0% | +0.0% | |
+1″ 125/65R19 | -0.0% | -0.0% | |
+2″ 125/55R20 | +0.0% | +0.0% |
235/40 R18 · 245/45 R17 · Methodology
What changed
- Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.