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.

Geometric comparison

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

Geometric comparison
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

Compare sizes

Current tireLooks valid

New tireLooks valid

Market

Units

Requires verificationWithin tolerance · Diameter +1.4% (+0.37 in) · US (~3%)

Requires verification · This rating covers tire geometry only, not vehicle compatibility.
Diameter +1.4% · Ride-height change +0.19 in.
Speedometer reads low · 60 mph → 60.8 mph.
Sidewall -0.31 in · Width +1.18 in.

Diameter+1.4%+0.37 in

Speedo @ 60+1.4%60 mph → 60.8 mph

Sidewall-0.31 inWidth +1.18 in

Ride-height change+0.19 inDiameter ÷ 2

How this result is calculated

Computed from nominal tire-size geometry: diameter, circumference and speedometer error. It does not check vehicle placard approval, load/speed rating, rim-width range, wheel-arch, suspension or brake clearance.

Methodology

Before fitting

Check the vehicle placard and owner’s manual first.
Match or exceed the required load index and speed rating.
Confirm rim-width range, bolt pattern, hub bore, offset and fasteners.
Inspect wheel-arch, suspension and brake clearance under real vehicle load.
Check TPMS, cold pressure and local roadworthiness rules.

Diameter: 26.31 in 26.68 in+0.37 in
Sidewall: 4.66 in 4.34 in-0.31 in
Width: 8.46 in 9.65 in+1.18 in
Circumference: 82.66 in 83.82 in+1.4%
Revs / mile: 767 756
Speedo @ 60: 60 mph 60.8 mph+1.4%
Ride-height change: 0.00 in +0.19 in
True distance per 100 indicated: 100 mi 101.4 mi+1.4%

Current — 215/55 R17
New — 245/45 R18
Grounded to the road: the axle rises +0.19 in.

Result report

215/55 R17 245/45 R18 · Requires verification · Within tolerance

Plan budget for this size: 245/45 R18

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Plan budget for this size

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Markdown link

[215/55 R17 vs 245/45 R18 Tire size comparison](https://tirefitlab.com/tire-size-calculator/?from=215%2F55+R17&to=245%2F45+R18&market=us)

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Budget$100–$140Per tire Mid-range$130–$185Per tire Premium$185–$260Per tire

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

In-tolerance alternative sizes

In-tolerance alternative sizes
Size	Diameter	Speedo @ 100	Use this
OE `215/55R17`	+0.0%	+0.0%
+1″ `235/45R18`	+0.1%	+0.1%

215/55 R17 · 245/45 R18 · Methodology

Technical check: 2026-06-28

What changed

Checked generated routes, metadata, sitemap inclusion and localized page rendering.

Methodology