225/40 R18 vs 215/50 R17

215/50 R17 stays within the configured tolerance for 225/40 R18: +1.5% diameter and +1.5% speedometer effect.

Geometric comparison

215/50 R17 stays within the configured tolerance for 225/40 R18: +1.5% diameter and +1.5% speedometer effect.

Geometric comparison
Metric	This size: 225/40 R18	Alternative: 215/50 R17	Difference	Verdict
Overall diameter	25.09 in	25.46 in	+1.5%	Within tolerance
Section width	8.86 in	8.46 in	-0.39 in	Computed difference
Sidewall height	3.54 in	4.23 in	+0.69 in	Computed difference
Circumference	78.81 in	80.00 in	+1.5%	Within tolerance
Speedo	0.0%	+1.5%	+1.5%	Within tolerance

Compare sizes

Current tireLooks valid

New tireLooks valid

Market

Units

Requires verificationWithin tolerance · Diameter +1.5% (+0.38 in) · US (~3%)

Requires verification · This rating covers tire geometry only, not vehicle compatibility.
Diameter +1.5% · Ride-height change +0.19 in.
Speedometer reads low · 60 mph → 60.9 mph.
Sidewall +0.69 in · Width -0.39 in.

Diameter+1.5%+0.38 in

Speedo @ 60+1.5%60 mph → 60.9 mph

Sidewall+0.69 inWidth -0.39 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: 25.09 in 25.46 in+0.38 in
Sidewall: 3.54 in 4.23 in+0.69 in
Width: 8.86 in 8.46 in-0.39 in
Circumference: 78.81 in 80.00 in+1.5%
Revs / mile: 804 792
Speedo @ 60: 60 mph 60.9 mph+1.5%
Ride-height change: 0.00 in +0.19 in
True distance per 100 indicated: 100 mi 101.5 mi+1.5%

Current — 225/40 R18
New — 215/50 R17
Grounded to the road: the axle rises +0.19 in.

Result report

225/40 R18 215/50 R17 · Requires verification · Within tolerance

Plan budget for this size: 215/50 R17

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Plan budget for this size

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Markdown link

[225/40 R18 vs 215/50 R17 Tire size comparison](https://tirefitlab.com/tire-size-calculator/?from=225%2F40+R18&to=215%2F50+R17&market=us)

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Budget$70–$95Per tire Mid-range$90–$125Per tire Premium$125–$180Per 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
−1″ `205/50R17`	-0.1%	-0.1%
OE `225/40R18`	+0.0%	+0.0%

225/40 R18 · 215/50 R17 · Methodology

Technical check: 2026-06-28

What changed

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

Methodology