Is 235/50R18 bigger than 215/60R16?

235/50R18 is 1.09 inches taller and 20 mm wider. In overall diameter that is +4.18%, which exceeds the ±3% rule of thumb for a substitution.

How much will 235/50R18 throw off my speedometer?

Every reading scales by 1.04184. An indicated 60 mph becomes 62.5 mph, and every 100 miles on the odometer is really 104.2 miles.

How much does 235/50R18 change ground clearance over 215/60R16?

The axle centerline moves by 0.55 inches — half the diameter change, because half the extra height sits below the hub and half above it.

Will 235/50R18 fit where 215/60R16 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.

215/60R16 vs 235/50R18

235/50R18 is +1.09″ in overall diameter and +20 mm in section width against 215/60R16 — a diameter change of +4.18%, which breaks the ±3% substitution rule. An indicated 60 mph would really be 62.5 mph.

Outside 3%

Every dimension

Difference between 215/60R16 and 235/50R18
Dimension	215/60R16 → 235/50R18	Change
Overall diameter	26.16″ → 27.25″	+1.09″ (+4.18%)
Section width	215 mm → 235 mm	+20 mm (+9.30%)
Sidewall height	129.0 mm → 117.5 mm	−11.5 mm
Rolling circumference	82.18″ → 85.61″	+3.44″
Revolutions per mile	771.0 → 740.1	−31.0
Axle height / clearance	13.08″ → 13.63″	+0.55″

215/60R16215 mm

235/50R18235 mm

215/60R16 26.16″235/50R18 27.25″

Which is taller, 215/60R16 or 235/50R18?

235/50R18 is the taller of the two, at 27.25″ against 26.16″. The gap is 1.09 inches, or 27.8 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. 215/60R16 is 215 mm wide with a 129.0 mm sidewall on a 16″ wheel; 235/50R18 is 235 mm wide with a 117.5 mm sidewall on a 18″ wheel.

What the speedometer will read

Indicated versus actual speed after the size change
Speedometer reads	Actual speed	Error
25 mph	26.0 mph	+1.0 mph
40 mph	41.7 mph	+1.7 mph
55 mph	57.3 mph	+2.3 mph
60 mph	62.5 mph	+2.5 mph
70 mph	72.9 mph	+2.9 mph
80 mph	83.3 mph	+3.3 mph

Fitting 235/50R18 in place of 215/60R16 multiplies every speed and distance reading by 1.04184. Over 10,000 indicated miles the odometer is out by +418 miles.

Effective gearing moves by the same proportion. A vehicle with 3.73 axles running 215/60R16 would need 3.89 to keep the same engine speed on 235/50R18. Work it out for your own axle ratio.

Full specification of each size

215/60R16

Derived dimensions for 215/60R16
Dimension	Metric	Imperial
Section width	215.0 mm	8.46″
Sidewall height	129.0 mm	5.08″
Wheel diameter	406.4 mm	16.0″
Overall diameter	664.4 mm	26.16″
Rolling circumference	2,087.3 mm	82.18″
Revolutions per mile	479.1 / km	771.0 / mile
Measuring rim (estimate)	165 mm	6.5″

235/50R18

Derived dimensions for 235/50R18
Dimension	Metric	Imperial
Section width	235.0 mm	9.25″
Sidewall height	117.5 mm	4.63″
Wheel diameter	457.2 mm	18.0″
Overall diameter	692.2 mm	27.25″
Rolling circumference	2,174.6 mm	85.61″
Revolutions per mile	459.9 / km	740.1 / mile
Measuring rim (estimate)	191 mm	7.5″

Rim widths differ too: 215/60R16 is designed for 6″–7.5″ and 235/50R18 for 7″–8.5″. 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 +4.18% exceeds the ±3% rule of thumb. Expect a speedometer error of about 2.5 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 235/50R18 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.