Question 1

Which tire is taller, 185/55 R16 or 175/65 R15?

Accepted Answer

185/55 R16 is taller by 1.4 mm (0.23%) compared with 175/65 R15.

Question 2

What is the diameter difference between 185/55 R16 and 175/65 R15?

Accepted Answer

185/55 R16 measures 610 mm overall diameter, 175/65 R15 measures 609 mm — a difference of 1.4 mm (0.23%).

Question 3

How much speedometer error does this change create?

Accepted Answer

Switching from 185/55 R16 to 175/65 R15 changes the speedometer reading by -0.23%. At an indicated 100 km/h, your true speed becomes about 99.8 km/h.

Question 4

Is 175/65 R15 a safe replacement for 185/55 R16?

Accepted Answer

Within ±3% diameter — generally considered a safe replacement from a speedometer-error standpoint, provided wheel offset, rim width and clearance also match your vehicle.

Question 5

What else should I check before changing tire size?

Accepted Answer

Beyond diameter and speedometer error, verify wheel offset (ET), rim width, hub bore, load index, brake and suspension clearance, and your vehicle's manufacturer specification. Local regulations may also limit how far you can deviate from OEM.

Metric	185/55 R16	175/65 R15	Difference
Overall diameter	609.9 mm	608.5 mm	-1.4 mm (-0.23%)
Sidewall height	101.8 mm	113.8 mm	+12.0 mm
Circumference	1.916 m	1.912 m	-4.4 mm
Revs / km	521.9	523.1	+1.2
Ground clearance	reference	-0.7 mm	-0.7 mm
Speedometer @ 100 km/h	100.0 km/h	99.8 km/h	-0.23 km/h

185/55 R16 vs 175/65 R15

Detailed comparison

Verdict: excellent

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