225/40 R18 vs 235/45 R17

235/45 R17 stays within the configured tolerance for 225/40 R18: +1.0% diameter and +1.0% speedometer effect.

Fitment verdict

235/45 R17 stays within the configured tolerance for 225/40 R18: +1.0% diameter and +1.0% speedometer effect.

Metric	This size: 225/40 R18	Alternative: 235/45 R17	Difference	Verdict
Overall diameter	25.09 in	25.33 in	+1.0%	Within tolerance
Section width	8.86 in	9.25 in	+0.39 in	Computed difference
Sidewall height	3.54 in	4.16 in	+0.62 in	Computed difference
Circumference	78.81 in	79.57 in	+1.0%	Within tolerance
Speedo	0.0%	+1.0%	+1.0%	Within tolerance

Current tireLooks valid

New tireLooks valid

Market

Units

✓ Within toleranceDiameter +1.0% (+0.24 in) · US (~3%)

Diameter+1.0%+0.24 in

Speedo @ 60+1.0%60 mph → 60.6 mph

Sidewall+0.62 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.

225/40 R18 235/45 R17 · Within tolerance

Use this size when shopping: 235/45 R17

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

Size	Diameter	Speedo @ 100
−1″ `205/50R17`	-0.1%	-0.1%
OE `225/40R18`	+0.0%	+0.0%
+1″ `155/50R19`	+0.1%	+0.1%
+2″ `215/30R20`	-0.0%	-0.0%

What changed

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