Question 1

Which tire is taller, 175/70 R13 or 185/55 R15?

Accepted Answer

185/55 R15 is taller by 9.3 mm (1.62%) compared with 175/70 R13.

Question 2

What is the diameter difference between 175/70 R13 and 185/55 R15?

Accepted Answer

175/70 R13 measures 575 mm overall diameter, 185/55 R15 measures 585 mm — a difference of 9.3 mm (1.62%).

Question 3

How much speedometer error does this change create?

Accepted Answer

Switching from 175/70 R13 to 185/55 R15 changes the speedometer reading by +1.62%. At an indicated 100 km/h, your true speed becomes about 101.6 km/h.

Question 4

Is 185/55 R15 a safe replacement for 175/70 R13?

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	175/70 R13	185/55 R15	Difference
Overall diameter	575.2 mm	584.5 mm	+9.3 mm (+1.62%)
Sidewall height	122.5 mm	101.8 mm	-20.8 mm
Circumference	1.807 m	1.836 m	+29.2 mm
Revs / km	553.4	544.6	-8.8
Ground clearance	reference	+4.6 mm	+4.6 mm
Speedometer @ 100 km/h	100.0 km/h	101.6 km/h	+1.62 km/h

175/70 R13 vs 185/55 R15

Detailed comparison

Verdict: excellent

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