285/30R20 tire size

A 285/30R20 tire is 26.73 inches (679.0 mm) tall, 11.22 in (285 mm) wide and fits a 20-inch wheel. In inch notation it is roughly a 26.7x11.2R20.

285/30R20 dimensions
Overall diameter	26.73 in	679.0 mm
Section width	11.22 in	285 mm
Sidewall height	3.37 in	85.5 mm
Circumference	83.98 in	2,133 mm
Revolutions	754.4 per mile	468.8 per km
Rim diameter	20 in	508.0 mm

Compare 285/30R20 with another size

Current size

New size

Speed in mphkm/h

Overall diameter difference

−0.52%

60 mph on the speedometer = 59.7 mph actual

Within the ±3 % diameter range most tire fitters accept.

Ground clearance: −1.8 mm (−0.07 in)
Revolutions: 754 → 758 per mile

285/30R20 335/25R20

Side-by-side dimensions

	Current	New	Difference	%
Diameter	26.73 in	26.59 in	−0.14 in	−0.52%
Diameter	679.0 mm	675.5 mm	−3.5 mm	−0.52%
Width	11.22 in	13.19 in	+1.97 in	+17.54%
Width	285.0 mm	335.0 mm	+50.0 mm	+17.54%
Sidewall	3.37 in	3.30 in	−0.07 in	−2.05%
Sidewall	85.5 mm	83.8 mm	−1.8 mm	−2.05%
Circumference	83.98 in	83.55 in	−0.43 in	−0.52%
Revs per mile	754.4	758.4	+3.9	+0.52%

Speedometer error

Speedometer shows	Actual speed	Difference
20 mph	19.9 mph	−0.1 mph
30 mph	29.8 mph	−0.2 mph
40 mph	39.8 mph	−0.2 mph
50 mph	49.7 mph	−0.3 mph
60 mph	59.7 mph	−0.3 mph
70 mph	69.6 mph	−0.4 mph
80 mph	79.6 mph	−0.4 mph

Alternative sizes on the same 20-inch wheel

Sizes in use within ±3 % of the overall diameter of 285/30R20:

Plus and minus sizes for 285/30R20

Size	Wheel	Diameter	Difference
275/40R18	Minus 2 (18 in)	26.66 in	−0.27%
285/40R18	Minus 2 (18 in)	26.98 in	+0.91%
255/45R18	Minus 2 (18 in)	27.04 in	+1.13%
265/40R18	Minus 2 (18 in)	26.35 in	−1.44%
325/30R19	Minus 1 (19 in)	26.68 in	−0.21%
285/35R19	Minus 1 (19 in)	26.85 in	+0.46%
275/35R19	Minus 1 (19 in)	26.58 in	−0.57%
255/40R19	Minus 1 (19 in)	27.03 in	+1.12%
295/25R21	Plus 1 (21 in)	26.81 in	+0.28%
265/30R21	Plus 1 (21 in)	27.26 in	+1.97%
275/30R21	Plus 1 (21 in)	27.50 in	+2.86%

Vehicles approved with 285/30R20 tires

Models whose Swiss type approval lists 285/30R20 as a standard or optional size (405 approvals in total). Always check your own vehicle's placard or papers.

Source: Swiss Federal Roads Office (FEDRO/ASTRA), open government data. Original data (downloaded 2026-09-29). Data processed by us; errors in processing are ours, not the publisher's.

Nearby 20-inch sizes

Reading the 285/30R20 size

285 — section width in millimetres (11.22 in).
30 — aspect ratio: the sidewall is 30 % of the width, 85.5 mm.
R — radial construction (ZR on the sidewall means a high-speed rated radial; the dimensions are the same).
20 — fits a 20-inch diameter wheel.

The load index and speed rating (for example 91V) follow the size on the sidewall. They must meet at least the values on your vehicle's tire placard.