245/45 R18 vs 245/40 R19

245/40 R19 stays within the configured tolerance for 245/45 R18: +0.1% diameter and +0.1% speedometer effect.

Fitment verdict

245/40 R19 stays within the configured tolerance for 245/45 R18: +0.1% diameter and +0.1% speedometer effect.

Metric	This size: 245/45 R18	Alternative: 245/40 R19	Difference	Verdict
Overall diameter	26.68 in	26.72 in	+0.1%	Within tolerance
Section width	9.65 in	9.65 in	0.00 in	Computed difference
Sidewall height	4.34 in	3.86 in	-0.48 in	Computed difference
Circumference	83.82 in	83.93 in	+0.1%	Within tolerance
Speedo	0.0%	+0.1%	+0.1%	Within tolerance

Current tireLooks valid

New tireLooks valid

Market

Units

✓ Within toleranceDiameter +0.1% (+0.04 in) · US (~3%)

Diameter+0.1%+0.04 in

Speedo @ 60+0.1%60 mph → 60.1 mph

Sidewall-0.48 inWidth +0.00 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.

245/45 R18 245/40 R19 · Within tolerance

Use this size when shopping: 245/40 R19

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

Size	Diameter	Speedo @ 100
−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%

What changed

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