Question 1

Which tire is taller, 165/70 R13 or 185/55 R15?

Accepted Answer

185/55 R15 is taller by 23.3 mm (4.15%) compared with 165/70 R13.

Question 2

What is the diameter difference between 165/70 R13 and 185/55 R15?

Accepted Answer

165/70 R13 measures 561 mm overall diameter, 185/55 R15 measures 585 mm — a difference of 23.3 mm (4.15%).

Question 3

How much speedometer error does this change create?

Accepted Answer

Switching from 165/70 R13 to 185/55 R15 changes the speedometer reading by +4.15%. At an indicated 100 km/h, your true speed becomes about 104.2 km/h.

Question 4

Is 185/55 R15 a safe replacement for 165/70 R13?

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	165/70 R13	185/55 R15	Difference
Overall diameter	561.2 mm	584.5 mm	+23.3 mm (+4.15%)
Sidewall height	115.5 mm	101.8 mm	-13.8 mm
Circumference	1.763 m	1.836 m	+73.2 mm
Revs / km	567.2	544.6	-22.6
Ground clearance	reference	+11.6 mm	+11.6 mm
Speedometer @ 100 km/h	100.0 km/h	104.2 km/h	+4.15 km/h

165/70 R13 vs 185/55 R15

Detailed comparison

Verdict: warning

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