225/45 R17 vs 225/40 R18

225/40 R18 stays within the configured tolerance for 225/45 R17: +0.5% diameter and +0.5% speedometer effect.

Fitment verdict

225/40 R18 stays within the configured tolerance for 225/45 R17: +0.5% diameter and +0.5% speedometer effect.

Metric	This size: 225/45 R17	Alternative: 225/40 R18	Difference	Verdict
Overall diameter	24.97 in	25.09 in	+0.5%	Within tolerance
Section width	8.86 in	8.86 in	0.00 in	Computed difference
Sidewall height	3.99 in	3.54 in	-0.44 in	Computed difference
Circumference	78.45 in	78.81 in	+0.5%	Within tolerance
Speedo	0.0%	+0.5%	+0.5%	Within tolerance

Current tireLooks valid

New tireLooks valid

Market

Units

✓ Within toleranceDiameter +0.5% (+0.11 in) · US (~3%)

Diameter+0.5%+0.11 in

Speedo @ 60+0.5%60 mph → 60.3 mph

Sidewall-0.44 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.

225/45 R17 225/40 R18 · Within tolerance

Use this size when shopping: 225/40 R18

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

Size	Diameter	Speedo @ 100
−1″ `285/40R16`	+0.0%	+0.0%
OE `225/45R17`	+0.0%	+0.0%
+1″ `295/30R18`	-0.0%	-0.0%
+2″ `305/25R19`	+0.1%	+0.1%

What changed

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