235/40 R18 vs 225/55 R16

225/55 R16 stays within the configured tolerance for 235/40 R18: +1.3% diameter and +1.3% speedometer effect.

Geometric comparison

225/55 R16 stays within the configured tolerance for 235/40 R18: +1.3% diameter and +1.3% speedometer effect.

Geometric comparison
Metric	This size: 235/40 R18	Alternative: 225/55 R16	Difference	Verdict
Overall diameter	25.40 in	25.74 in	+1.3%	Within tolerance
Section width	9.25 in	8.86 in	-0.39 in	Computed difference
Sidewall height	3.70 in	4.87 in	+1.17 in	Computed difference
Circumference	79.80 in	80.88 in	+1.3%	Within tolerance
Speedo	0.0%	+1.3%	+1.3%	Within tolerance

Compare sizes

Current tireLooks valid

New tireLooks valid

Market

Units

High fitment riskWithin tolerance · Diameter +1.3% (+0.34 in) · US (~3%)

High fitment risk · This rating covers tire geometry only, not vehicle compatibility.
Diameter +1.3% · Ride-height change +0.17 in.
Speedometer reads low · 60 mph → 60.8 mph.
Sidewall +1.17 in · Width -0.39 in.

Diameter+1.3%+0.34 in

Speedo @ 60+1.3%60 mph → 60.8 mph

Sidewall+1.17 inWidth -0.39 in

Ride-height change+0.17 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: 25.40 in 25.74 in+0.34 in
Sidewall: 3.70 in 4.87 in+1.17 in
Width: 9.25 in 8.86 in-0.39 in
Circumference: 79.80 in 80.88 in+1.3%
Revs / mile: 794 783
Speedo @ 60: 60 mph 60.8 mph+1.3%
Ride-height change: 0.00 in +0.17 in
True distance per 100 indicated: 100 mi 101.3 mi+1.3%

Current — 235/40 R18
New — 225/55 R16
Grounded to the road: the axle rises +0.17 in.

Result report

235/40 R18 225/55 R16 · High fitment risk · Within tolerance

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Markdown link

[235/40 R18 vs 225/55 R16 Tire size comparison](https://tirefitlab.com/tire-size-calculator/?from=235%2F40+R18&to=225%2F55+R16&market=us)

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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 `235/40R18`	+0.0%	+0.0%

235/40 R18 · 225/55 R16 · Methodology

Technical check: 2026-06-28

What changed

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

Methodology