Is 225/50R17 bigger than 205/65R15?

225/50R17 is 0.37 inches taller and 20 mm wider. In overall diameter that is +1.44%, which stays inside the ±3% rule of thumb for a substitution.

How much will 225/50R17 throw off my speedometer?

Every reading scales by 1.01436. An indicated 60 mph becomes 60.9 mph, and every 100 miles on the odometer is really 101.4 miles.

How much does 225/50R17 change ground clearance over 205/65R15?

The axle centerline moves by 0.18 inches — half the diameter change, because half the extra height sits below the hub and half above it.

Will 225/50R17 fit where 205/65R15 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.

205/65R15 vs 225/50R17

225/50R17 is +0.37″ in overall diameter and +20 mm in section width against 205/65R15 — a diameter change of +1.44%, which stays inside the ±3% substitution rule. An indicated 60 mph would really be 60.9 mph.

Within 3%

Every dimension

Difference between 205/65R15 and 225/50R17
Dimension	205/65R15 → 225/50R17	Change
Overall diameter	25.49″ → 25.86″	+0.37″ (+1.44%)
Section width	205 mm → 225 mm	+20 mm (+9.76%)
Sidewall height	133.3 mm → 112.5 mm	−20.8 mm
Rolling circumference	80.09″ → 81.24″	+1.15″
Revolutions per mile	791.2 → 779.9	−11.2
Axle height / clearance	12.75″ → 12.93″	+0.18″

205/65R15205 mm

225/50R17225 mm

205/65R15 25.49″225/50R17 25.86″

Which is taller, 205/65R15 or 225/50R17?

225/50R17 is the taller of the two, at 25.86″ against 25.49″. The gap is 0.37 inches, or 9.3 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. 205/65R15 is 205 mm wide with a 133.3 mm sidewall on a 15″ wheel; 225/50R17 is 225 mm wide with a 112.5 mm sidewall on a 17″ wheel.

What the speedometer will read

Indicated versus actual speed after the size change
Speedometer reads	Actual speed	Error
25 mph	25.4 mph	+0.4 mph
40 mph	40.6 mph	+0.6 mph
55 mph	55.8 mph	+0.8 mph
60 mph	60.9 mph	+0.9 mph
70 mph	71.0 mph	+1.0 mph
80 mph	81.1 mph	+1.1 mph

Fitting 225/50R17 in place of 205/65R15 multiplies every speed and distance reading by 1.01436. Over 10,000 indicated miles the odometer is out by +144 miles.

Effective gearing moves by the same proportion. A vehicle with 3.73 axles running 205/65R15 would need 3.78 to keep the same engine speed on 225/50R17. Work it out for your own axle ratio.

Full specification of each size

205/65R15

Derived dimensions for 205/65R15
Dimension	Metric	Imperial
Section width	205.0 mm	8.07″
Sidewall height	133.3 mm	5.25″
Wheel diameter	381.0 mm	15.0″
Overall diameter	647.5 mm	25.49″
Rolling circumference	2,034.2 mm	80.09″
Revolutions per mile	491.6 / km	791.2 / mile
Measuring rim (estimate)	152 mm	6″

225/50R17

Derived dimensions for 225/50R17
Dimension	Metric	Imperial
Section width	225.0 mm	8.86″
Sidewall height	112.5 mm	4.43″
Wheel diameter	431.8 mm	17.0″
Overall diameter	656.8 mm	25.86″
Rolling circumference	2,063.4 mm	81.24″
Revolutions per mile	484.6 / km	779.9 / mile
Measuring rim (estimate)	191 mm	7.5″

Rim widths differ too: 205/65R15 is designed for 5.5″–7″ and 225/50R17 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?

Inside the ±3% rule

The diameter difference of +1.44% is within the ±3% that fitters use as the boundary for a substitution, so the speedometer, odometer and wheel-speed-derived systems stay close enough to calibration. The section width difference of +20 mm is a separate question and is the one that decides whether it rubs.

Neither figure says anything about physical fitment. Whether 225/50R17 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.