245/45 R18 vs 245/35 R20

245/35 R20 stays within the configured tolerance for 245/45 R18: +0.3% diameter and +0.3% speedometer effect.

Geometric comparison

245/35 R20 stays within the configured tolerance for 245/45 R18: +0.3% diameter and +0.3% speedometer effect.

Geometric comparison
Metric	This size: 245/45 R18	Alternative: 245/35 R20	Difference	Verdict
Overall diameter	26.68 in	26.75 in	+0.3%	Within tolerance
Section width	9.65 in	9.65 in	0.00 in	Computed difference
Sidewall height	4.34 in	3.38 in	-0.96 in	Computed difference
Circumference	83.82 in	84.04 in	+0.3%	Within tolerance
Speedo	0.0%	+0.3%	+0.3%	Within tolerance

Compare sizes

Current tireLooks valid

New tireLooks valid

Market

Units

Requires verificationWithin tolerance · Diameter +0.3% (+0.07 in) · US (~3%)

Requires verification · This rating covers tire geometry only, not vehicle compatibility.
Diameter +0.3% · Ride-height change +0.04 in.
Speedometer reads low · 60 mph → 60.2 mph.
Sidewall -0.96 in · Width +0.00 in.

Diameter+0.3%+0.07 in

Speedo @ 60+0.3%60 mph → 60.2 mph

Sidewall-0.96 inWidth +0.00 in

Ride-height change+0.04 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: 26.68 in 26.75 in+0.07 in
Sidewall: 4.34 in 3.38 in-0.96 in
Width: 9.65 in 9.65 in+0.00 in
Circumference: 83.82 in 84.04 in+0.3%
Revs / mile: 756 754
Speedo @ 60: 60 mph 60.2 mph+0.3%
Ride-height change: 0.00 in +0.04 in
True distance per 100 indicated: 100 mi 100.3 mi+0.3%

Current — 245/45 R18
New — 245/35 R20
Grounded to the road: the axle rises +0.04 in.

Result report

245/45 R18 245/35 R20 · Requires verification · Within tolerance

Plan budget for this size: 245/35 R20

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Plan budget for this size

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Markdown link

[245/45 R18 vs 245/35 R20 Tire size comparison](https://tirefitlab.com/tire-size-calculator/?from=245%2F45+R18&to=245%2F35+R20&market=us)

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Budget$150–$210Per tire Mid-range$195–$280Per tire Premium$280–$395Per 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 `245/45R18`	+0.0%	+0.0%

245/45 R18 · 245/35 R20 · Methodology

Technical check: 2026-06-28

What changed

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

Methodology