215/55 R16 vs 235/40 R18

What changes when you change tire size?

235/40 R18 stays within the configured tolerance for 215/55 R16: +0.4% diameter and +0.4% speedometer effect.

Geometric comparison

Geometric comparison
Metric	This size: 215/55 R16	Alternative: 235/40 R18	Difference	Verdict
Overall diameter	25.31 in	25.40 in	+0.4%	Within tolerance
Section width	8.46 in	9.25 in	+0.79 in	Computed difference
Sidewall height	4.66 in	3.70 in	-0.95 in	Computed difference
Circumference	79.52 in	79.80 in	+0.4%	Within tolerance
Speedo	0.0%	+0.4%	+0.4%	Within tolerance

Compare sizes

Current tireLooks valid

New tireLooks valid

Editorial preset

Units

Editorial preset

These are TireFitLab editorial diameter-screening presets. Regional names choose a preset, not a national legal limit, ETRTO rule or vehicle approval. The AWD preset does not establish an allowable drivetrain mismatch. Use the exact vehicle and tyre manufacturer instructions; nominal geometry alone cannot approve fitment.

Requires verificationWithin tolerance · Diameter +0.4% (+0.09 in) · US preset (±3%)

Requires verification · This rating covers tire geometry only, not vehicle compatibility.
Diameter +0.4% · Ride-height change +0.05 in.
Speedometer reads low · 60 mph → 60.2 mph.
Sidewall -0.95 in · Width +0.79 in.

Diameter+0.4%+0.09 in

Speedo @ 60+0.4%60 mph → 60.2 mph

Sidewall-0.95 inWidth +0.79 in

Ride-height change+0.05 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: 25.31 in 25.40 in+0.09 in
Sidewall: 4.66 in 3.70 in-0.95 in
Width: 8.46 in 9.25 in+0.79 in
Circumference: 79.52 in 79.80 in+0.4%
Revs / mile: 797 794
Speedo @ 60: 60 mph 60.2 mph+0.4%
Ride-height change: 0.00 in +0.05 in
True distance per 100 indicated: 100 mi 100.4 mi+0.4%

Current — 215/55 R16
New — 235/40 R18
Grounded to the road: the axle rises +0.05 in.

Tires and wheels in one comparison

Include wheel width and offset

Result report

215/55 R16 235/40 R18 · Requires verification · Within tolerance

Plan budget for this size: 235/40 R18

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Plan budget for this size

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Markdown link

[215/55 R16 vs 235/40 R18 Tire size comparison](https://tirefitlab.com/tire-size-calculator/?from=215%2F55+R16&to=235%2F40+R18&market=us&units=imperial)

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Estimated budgetBudget$85–$120Per tire Mid-range$110–$160Per tire Premium$160–$225Per tire

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

In-tolerance alternative sizes

In-tolerance alternative sizes
Size	Diameter	Speedo @ 100
−1″ `215/60R15`	-0.6%	-0.6%
OE `215/55R16`	+0.0%	+0.0%
+1″ `215/50R17`	+0.6%	+0.6%
+2″ `215/45R18`	+1.2%	+1.2%

215/55 R16 · 235/40 R18 · Methodology