275/60R20 vs 305/55R20

305/55R20 is 0.2" taller than 275/60R20 (0.7%)

Diameter difference+0.66%diameter 32.99" → 33.21"
275/60R20305/55R20
275/60R20305/55R20Difference
Overall diameter32.99"33.21"+0.22"
Section width10.83"12.01"+1.18"
Sidewall height6.50"6.60"+0.11"
Circumference103.6"104.3"+0.7"
Revolutions per mile611607−4
Wheel diameter20"20"±0"

Speedometer

ShowsActualDiff
30 mph30.2 mph+0.2
45 mph45.3 mph+0.3
60 mph60.4 mph+0.4
70 mph70.5 mph+0.5
80 mph80.5 mph+0.5

Gear ratio to match

CurrentEquivalent
3.423.44
3.553.57
3.733.75
4.104.13

305/55R20 is 0.22" taller than 275/60R20, a +0.66% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.11" (half the diameter change), and the tire needs 0.11" more room above it.

305/55R20 is 1.18" wider. On the same wheel offset about half of that, 0.59", moves toward the suspension and half toward the fender.

Both fit a 20" wheel; the sidewall is 0.11" taller on 305/55R20.

Details: 275/60R20 in inches · 305/55R20 in inches · change sizes in the calculator

FAQ

What is the difference between 275/60R20 and 305/55R20?

305/55R20 is 0.22" taller (+0.66%) and 1.18" wider than 275/60R20.

Will 305/55R20 change my speedometer?

Yes, by +0.66%. When the speedometer shows 60 mph you would be going 60.4 mph.

Can I replace 275/60R20 with 305/55R20?

Often yes: the diameter change of +0.7% is within the common 3% guideline. Check the load index, speed rating and clearance.