215/55 R17 vs 245/45 R18

245/45 R18 stays within the configured tolerance for 215/55 R17: +1.4% diameter and +1.4% speedometer effect.

Fitment verdict

245/45 R18 stays within the configured tolerance for 215/55 R17: +1.4% diameter and +1.4% speedometer effect.

Metric	This size: 215/55 R17	Alternative: 245/45 R18	Difference	Verdict
Overall diameter	26.31 in	26.68 in	+1.4%	Within tolerance
Section width	8.46 in	9.65 in	+1.18 in	Computed difference
Sidewall height	4.66 in	4.34 in	-0.31 in	Computed difference
Circumference	82.66 in	83.82 in	+1.4%	Within tolerance
Speedo	0.0%	+1.4%	+1.4%	Within tolerance

Current tireLooks valid

New tireLooks valid

Market

Units

✓ Within toleranceDiameter +1.4% (+0.37 in) · US (~3%)

Diameter+1.4%+0.37 in

Speedo @ 60+1.4%60 mph → 60.8 mph

Sidewall-0.31 inWidth +1.18 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.

215/55 R17 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″ `175/75R16`	+0.1%	+0.1%
OE `215/55R17`	+0.0%	+0.0%
+1″ `235/45R18`	+0.1%	+0.1%
+2″ `265/35R19`	-0.0%	-0.0%

What changed

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