Question 1

Which tire is taller, 145/70 R13 or 185/55 R15?

Accepted Answer

185/55 R15 is taller by 51.3 mm (9.62%) compared with 145/70 R13.

Question 2

What is the diameter difference between 145/70 R13 and 185/55 R15?

Accepted Answer

145/70 R13 measures 533 mm overall diameter, 185/55 R15 measures 585 mm — a difference of 51.3 mm (9.62%).

Question 3

How much speedometer error does this change create?

Accepted Answer

Switching from 145/70 R13 to 185/55 R15 changes the speedometer reading by +9.62%. At an indicated 100 km/h, your true speed becomes about 109.6 km/h.

Question 4

Is 185/55 R15 a safe replacement for 145/70 R13?

Accepted Answer

Over 5% diameter difference. This is outside the common safe range and can affect speedometer accuracy, ABS calibration and gearing. Not recommended without professional review.

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	145/70 R13	185/55 R15	Difference
Overall diameter	533.2 mm	584.5 mm	+51.3 mm (+9.62%)
Sidewall height	101.5 mm	101.8 mm	+0.3 mm
Circumference	1.675 m	1.836 m	+161.2 mm
Revs / km	597.0	544.6	-52.4
Ground clearance	reference	+25.6 mm	+25.6 mm
Speedometer @ 100 km/h	100.0 km/h	109.6 km/h	+9.62 km/h

145/70 R13 vs 185/55 R15

Detailed comparison

Verdict: danger

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