Is 285/45R22 bigger than 245/50R20?

285/45R22 is 2.45 inches taller and 40 mm wider. In overall diameter that is +8.27%, which exceeds the ±3% rule of thumb for a substitution.

How much will 285/45R22 throw off my speedometer?

Every reading scales by 1.08274. An indicated 60 mph becomes 65.0 mph, and every 100 miles on the odometer is really 108.3 miles.

How much does 285/45R22 change ground clearance over 245/50R20?

The axle centerline moves by 1.23 inches — half the diameter change, because half the extra height sits below the hub and half above it.

Will 285/45R22 fit where 245/50R20 fits?

Nothing derived from the size code can answer that. Clearance depends on wheel offset, suspension travel and body dimensions that no tire size contains. This page tells you exactly what changes dimensionally, which is the part that can be calculated.

245/50R20 vs 285/45R22

285/45R22 is +2.45″ in overall diameter and +40 mm in section width against 245/50R20 — a diameter change of +8.27%, which breaks the ±3% substitution rule. An indicated 60 mph would really be 65.0 mph.

Outside 3%

Every dimension

Difference between 245/50R20 and 285/45R22
Dimension	245/50R20 → 285/45R22	Change
Overall diameter	29.65″ → 32.10″	+2.45″ (+8.27%)
Section width	245 mm → 285 mm	+40 mm (+16.33%)
Sidewall height	122.5 mm → 128.3 mm	+5.8 mm
Rolling circumference	93.13″ → 100.84″	+7.71″
Revolutions per mile	680.3 → 628.3	−52.0
Axle height / clearance	14.82″ → 16.05″	+1.23″

245/50R20245 mm

285/45R22285 mm

245/50R20 29.65″285/45R22 32.10″

Which is taller, 245/50R20 or 285/45R22?

285/45R22 is the taller of the two, at 32.10″ against 29.65″. The gap is 2.45 inches, or 62.3 mm.

Both are metric sizes, so neither states its height directly. Both figures below are derived from the section width, aspect ratio and wheel diameter in the code. 245/50R20 is 245 mm wide with a 122.5 mm sidewall on a 20″ wheel; 285/45R22 is 285 mm wide with a 128.3 mm sidewall on a 22″ wheel.

What the speedometer will read

Indicated versus actual speed after the size change
Speedometer reads	Actual speed	Error
25 mph	27.1 mph	+2.1 mph
40 mph	43.3 mph	+3.3 mph
55 mph	59.6 mph	+4.6 mph
60 mph	65.0 mph	+5.0 mph
70 mph	75.8 mph	+5.8 mph
80 mph	86.6 mph	+6.6 mph

Fitting 285/45R22 in place of 245/50R20 multiplies every speed and distance reading by 1.08274. Over 10,000 indicated miles the odometer is out by +827 miles.

Effective gearing moves by the same proportion. A vehicle with 3.73 axles running 245/50R20 would need 4.04 to keep the same engine speed on 285/45R22. Work it out for your own axle ratio.

Full specification of each size

245/50R20

Derived dimensions for 245/50R20
Dimension	Metric	Imperial
Section width	245.0 mm	9.65″
Sidewall height	122.5 mm	4.82″
Wheel diameter	508.0 mm	20.0″
Overall diameter	753.0 mm	29.65″
Rolling circumference	2,365.6 mm	93.13″
Revolutions per mile	422.7 / km	680.3 / mile
Measuring rim (estimate)	203 mm	8″

285/45R22

Derived dimensions for 285/45R22
Dimension	Metric	Imperial
Section width	285.0 mm	11.22″
Sidewall height	128.3 mm	5.05″
Wheel diameter	558.8 mm	22.0″
Overall diameter	815.3 mm	32.10″
Rolling circumference	2,561.3 mm	100.84″
Revolutions per mile	390.4 / km	628.3 / mile
Measuring rim (estimate)	241 mm	9.5″

Rim widths differ too: 245/50R20 is designed for 7.5″–9″ and 285/45R22 for 9″–10.5″. Their measuring rims differ, so the same wheel will not be ideal for both.

Can you swap one for the other?

Outside the ±3% rule

The diameter difference of +8.27% exceeds the ±3% rule of thumb. Expect a speedometer error of about 5.0 mph at an indicated 60, and an odometer that is off by the same proportion. It is a common swap even so — it just needs the instruments recalibrated to stay honest.

Neither figure says anything about physical fitment. Whether 285/45R22 clears the strut, the fender liner and the steering stops depends on wheel offset and suspension geometry that a size code does not encode. For maintenance rather than sizing, Car Basics covers tire care.