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.

Fitment verdict

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

Current tireLooks valid

New tireLooks valid

Market

Units

✓ Within toleranceDiameter +1.5% (+0.38 in) · US (~3%)

Diameter+1.5%+0.38 in

Speedo @ 60+1.5%60 mph → 60.9 mph

Sidewall-1.31 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.

205/70 R15 245/45 R18 · Within tolerance

Use this size when shopping: 245/45 R18

Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.

Size	Diameter	Speedo @ 100
−1″ `195/80R14`	-0.1%	-0.1%
OE `205/70R15`	+0.0%	+0.0%
+1″ `175/75R16`	+0.1%	+0.1%
+2″ `295/40R17`	-0.0%	-0.0%

What changed

Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.