Question 1

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

Accepted Answer

175/65 R15 is taller by 24.0 mm (3.94%) compared with 185/55 R15.

Question 2

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

Accepted Answer

175/65 R15 measures 609 mm overall diameter, 185/55 R15 measures 585 mm — a difference of 24.0 mm (3.94%).

Question 3

How much speedometer error does this change create?

Accepted Answer

Switching from 175/65 R15 to 185/55 R15 changes the speedometer reading by -3.94%. At an indicated 100 km/h, your true speed becomes about 96.1 km/h.

Question 4

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

Accepted Answer

Between 3% and 5% diameter difference — speedometer drift is noticeable. Consider recalibration and confirm clearance with your vehicle's manufacturer specification.

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	175/65 R15	185/55 R15	Difference
Overall diameter	608.5 mm	584.5 mm	-24.0 mm (-3.94%)
Sidewall height	113.8 mm	101.8 mm	-12.0 mm
Circumference	1.912 m	1.836 m	-75.4 mm
Revs / km	523.1	544.6	+21.5
Ground clearance	reference	-12.0 mm	-12.0 mm
Speedometer @ 100 km/h	100.0 km/h	96.1 km/h	-3.94 km/h

175/65 R15 vs 185/55 R15

Detailed comparison

Verdict: warning

Related comparisons

Frequently asked questions