Is 285/75R16 bigger than 235/75R15?

285/75R16 is 3.95 inches taller and 50 mm wider. In overall diameter that is +13.69%, which exceeds the ±3% rule of thumb for a substitution.

How much will 285/75R16 throw off my speedometer?

Every reading scales by 1.13688. An indicated 60 mph becomes 68.2 mph, and every 100 miles on the odometer is really 113.7 miles.

How much does 285/75R16 change ground clearance over 235/75R15?

The axle centerline moves by 1.98 inches — half the diameter change, because half the extra height sits below the hub and half above it.

Will 285/75R16 fit where 235/75R15 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.

235/75R15 vs 285/75R16

285/75R16 is +3.95″ in overall diameter and +50 mm in section width against 235/75R15 — a diameter change of +13.69%, which breaks the ±3% substitution rule. An indicated 60 mph would really be 68.2 mph.

Outside 3%

Every dimension

Difference between 235/75R15 and 285/75R16
Dimension	235/75R15 → 285/75R16	Change
Overall diameter	28.88″ → 32.83″	+3.95″ (+13.69%)
Section width	235 mm → 285 mm	+50 mm (+21.28%)
Sidewall height	176.3 mm → 213.8 mm	+37.5 mm
Rolling circumference	90.72″ → 103.14″	+12.42″
Revolutions per mile	698.4 → 614.3	−84.1
Axle height / clearance	14.44″ → 16.42″	+1.98″

235/75R15235 mm

285/75R16285 mm

235/75R15 28.88″285/75R16 32.83″

Which is taller, 235/75R15 or 285/75R16?

285/75R16 is the taller of the two, at 32.83″ against 28.88″. The gap is 3.95 inches, or 100.4 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. 235/75R15 is 235 mm wide with a 176.3 mm sidewall on a 15″ wheel; 285/75R16 is 285 mm wide with a 213.8 mm sidewall on a 16″ wheel.

What the speedometer will read

Indicated versus actual speed after the size change
Speedometer reads	Actual speed	Error
25 mph	28.4 mph	+3.4 mph
40 mph	45.5 mph	+5.5 mph
55 mph	62.5 mph	+7.5 mph
60 mph	68.2 mph	+8.2 mph
70 mph	79.6 mph	+9.6 mph
80 mph	91.0 mph	+11.0 mph

Fitting 285/75R16 in place of 235/75R15 multiplies every speed and distance reading by 1.13688. Over 10,000 indicated miles the odometer is out by +1,369 miles.

Effective gearing moves by the same proportion. A vehicle with 3.73 axles running 235/75R15 would need 4.24 to keep the same engine speed on 285/75R16. Work it out for your own axle ratio.

Full specification of each size

235/75R15

Derived dimensions for 235/75R15
Dimension	Metric	Imperial
Section width	235.0 mm	9.25″
Sidewall height	176.3 mm	6.94″
Wheel diameter	381.0 mm	15.0″
Overall diameter	733.5 mm	28.88″
Rolling circumference	2,304.4 mm	90.72″
Revolutions per mile	434.0 / km	698.4 / mile
Measuring rim (estimate)	165 mm	6.5″

285/75R16

Derived dimensions for 285/75R16
Dimension	Metric	Imperial
Section width	285.0 mm	11.22″
Sidewall height	213.8 mm	8.42″
Wheel diameter	406.4 mm	16.0″
Overall diameter	833.9 mm	32.83″
Rolling circumference	2,619.8 mm	103.14″
Revolutions per mile	381.7 / km	614.3 / mile
Measuring rim (estimate)	203 mm	8″

Rim widths differ too: 235/75R15 is designed for 6″–7.5″ and 285/75R16 for 7.5″–9″. 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 +13.69% exceeds the ±3% rule of thumb. Expect a speedometer error of about 8.2 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 285/75R16 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.