What is the diameter difference between 185/60R15 and 205/50R17?

185/60R15 has an overall diameter of 23.74 inches (603 mm). 205/50R17 is 25.07 inches (637 mm). That's a 1.33 inch (34 mm) difference — 205/50R17 is taller.

Will 205/50R17 cause speedometer error on a car fitted with 185/60R15?

Swapping 185/60R15 for 205/50R17 produces a speedometer error of about 5.6%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 63.4 mph. Anything under 3% is usually acceptable without recalibration.

How many revolutions per mile does each size do?

185/60R15 turns 850 revs per mile. 205/50R17 turns 804 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.

What's the sidewall height difference?

185/60R15 has a sidewall of 111 mm (4.37 in). 205/50R17 sidewall is 103 mm (4.04 in). Lower-profile sidewalls give sharper steering response but less bump compliance.

Is 205/50R17 a safe plus-size upgrade from 185/60R15?

A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 5.6%. This swap is outside the typical ±3% safe range and may require speedometer recalibration or affect ABS / traction control behaviour.

Tire size comparison

185/60R15 vs 205/50R17

Overall diameter, sidewall, revs per mile, and speedometer error — 205/50R17 is the taller tire, with a 5.6% speedo delta when swapping.

185/60R15

23.74in

603 mm overall diameter

205/50R17

25.07in

637 mm overall diameter

Diameter Δ

1.33 in

Speedo error

5.6%

185/60R15 revs/mi

850

205/50R17 revs/mi

804

Outside the typical ±3% safe plus-size band — you may want speedometer recalibration, and this change can affect ABS or traction control behaviour.

Full spec

Side by side

Metric	185/60R15	205/50R17
Section width	185 mm	205 mm
Aspect ratio	60	50
Wheel diameter	15″	17″
Sidewall height	111 mm	103 mm
Overall diameter	23.74 in (603 mm)	25.07 in (637 mm)
Circumference	74.58 in	78.76 in
Revolutions / mile	850	804

Other comparisons for these sizes

175/65R14 vs 185/60R15 185/65R14 vs 185/60R15 185/60R15 vs 195/60R15 205/55R16 vs 205/50R17 205/50R17 vs 225/40R19 205/50R17 vs 215/50R17 205/50R17 vs 225/50R17

FAQ

Frequently asked

What is the diameter difference between 185/60R15 and 205/50R17?: 185/60R15 has an overall diameter of 23.74 inches (603 mm). 205/50R17 is 25.07 inches (637 mm). That's a 1.33 inch (34 mm) difference — 205/50R17 is taller.
Will 205/50R17 cause speedometer error on a car fitted with 185/60R15?: Swapping 185/60R15 for 205/50R17 produces a speedometer error of about 5.6%. Your speedometer will read lower than your actual speed — a 60 mph indicated reading is really 63.4 mph. Anything under 3% is usually acceptable without recalibration.
How many revolutions per mile does each size do?: 185/60R15 turns 850 revs per mile. 205/50R17 turns 804 revs per mile. Taller tyres turn fewer times per mile, which lowers effective final-drive ratio.
What's the sidewall height difference?: 185/60R15 has a sidewall of 111 mm (4.37 in). 205/50R17 sidewall is 103 mm (4.04 in). Lower-profile sidewalls give sharper steering response but less bump compliance.
Is 205/50R17 a safe plus-size upgrade from 185/60R15?: A plus-size upgrade is considered safe when overall diameter stays within ±3% — here the difference is 5.6%. This swap is outside the typical ±3% safe range and may require speedometer recalibration or affect ABS / traction control behaviour.