205/70 R15 vs 245/45 R18
205/70 R15 vs 245/45 R18
245/45 R18 stays within the configured tolerance for 205/70 R15: +1.5% diameter and +1.5% speedometer effect.
Geometric comparison
245/45 R18 stays within the configured tolerance for 205/70 R15: +1.5% diameter and +1.5% speedometer effect.
| Metric | This size: 205/70 R15 | Alternative: 245/45 R18 | Difference | Verdict |
|---|---|---|---|---|
| Overall diameter | 26.30 in | 26.68 in | +1.5% | Within tolerance |
| Section width | 8.07 in | 9.65 in | +1.57 in | Computed difference |
| Sidewall height | 5.65 in | 4.34 in | -1.31 in | Computed difference |
| Circumference | 82.62 in | 83.82 in | +1.5% | Within tolerance |
| Speedo | 0.0% | +1.5% | +1.5% | Within tolerance |
Compare sizes
Looks valid
Looks valid
Units
High fitment riskWithin tolerance · Diameter +1.5% (+0.38 in) · US (~3%)
- High fitment risk · This rating covers tire geometry only, not vehicle compatibility.
- Diameter +1.5% · Ride-height change +0.19 in.
- Speedometer reads low · 60 mph → 60.9 mph.
- Sidewall -1.31 in · Width +1.57 in.
Diameter+1.5%+0.38 in
Speedo @ 60+1.5%60 mph → 60.9 mph
Sidewall-1.31 inWidth +1.57 in
Ride-height change+0.19 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.
MethodologyBefore 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
- 26.30 in 26.68 in+0.38 in
- Sidewall
- 5.65 in 4.34 in-1.31 in
- Width
- 8.07 in 9.65 in+1.57 in
- Circumference
- 82.62 in 83.82 in+1.5%
- Revs / mile
- 767 756
- Speedo @ 60
- 60 mph 60.9 mph+1.5%
- Ride-height change
- 0.00 in +0.19 in
- True distance per 100 indicated
- 100 mi 101.5 mi+1.5%
- Current —
205/70 R15 - New —
245/45 R18 - Grounded to the road: the axle rises +0.19 in.
Result report
205/70 R15 245/45 R18 · High fitment risk · Within tolerance
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Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.
In-tolerance alternative sizes
| Size | Diameter | Speedo @ 100 | Use this |
|---|---|---|---|
−1″ 195/80R14 | -0.1% | -0.1% | |
OE 205/70R15 | +0.0% | +0.0% | |
+1″ 175/75R16 | +0.1% | +0.1% |
205/70 R15 · 245/45 R18 · Methodology
- Technical check
- 2026-06-28
What changed
- Checked generated routes, metadata, sitemap inclusion and localized page rendering.