155/80R13 vs 185/70R13

185/70R13 is 0.43 in (11.0 mm) taller than 155/80R13, a +1.90% diameter difference. With the speedometer set for 155/80R13, an indicated 60 mph is 61.1 mph on 185/70R13.

Is this a safe swap?

Diameter difference +1.90%: within the ±3% guideline

By overall diameter alone, 185/70R13 falls inside the ±3% range commonly used as a guideline when replacing 155/80R13. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

155/80R13 vs 185/70R13 differences
Measurement	155/80R13	185/70R13	Difference	% diff
Overall diameter	22.76 in (578.2 mm)	23.20 in (589.2 mm)	+0.43 in (+11.0 mm)	+1.90%
Sidewall height	4.88 in (124.0 mm)	5.10 in (129.5 mm)	+0.22 in (+5.5 mm)	+4.44%
Section width	6.10 in (155.0 mm)	7.28 in (185.0 mm)	+1.18 in (+30.0 mm)	+19.35%
Circumference	71.51 in (1,816.5 mm)	72.88 in (1,851.0 mm)	+1.36 in (+34.6 mm)	+1.90%
Revolutions per mile	886	869	−17	−1.87%

True speed with the speedometer calibrated for 155/80R13
Indicated	Actual on 155/80R13	Actual on 185/70R13	Difference
30 mph	30.0 mph	30.6 mph	+0.6 mph
60 mph	60.0 mph	61.1 mph	+1.1 mph
75 mph	75.0 mph	76.4 mph	+1.4 mph

Ride-height change: 185/70R13 raises the vehicle by 0.22 in (5.5 mm) at the axle (half the +11.0 mm diameter difference).

185/70R13 is 0.43 in taller than 155/80R13 and 30 mm wider, a 1.90% difference in overall diameter.

With the speedometer calibrated for 155/80R13, an indicated 60 mph is actually 61.1 mph on 185/70R13, and revolutions per mile change from 886 to 869.

Both sizes mount on 13-inch wheels.

Size pages

Other comparisons with 155/80R13

Other comparisons with 185/70R13

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.