305/50R20 vs 305/55R20

305/55R20 is 1.2" taller than 305/50R20 (3.8%)

Diameter difference+3.75%diameter 32.01" → 33.21"
305/50R20305/55R20
305/50R20305/55R20Difference
Overall diameter32.01"33.21"+1.20"
Section width12.01"12.01"±0.00"
Sidewall height6.00"6.60"+0.60"
Circumference100.6"104.3"+3.8"
Revolutions per mile630607−23
Wheel diameter20"20"±0"

Speedometer

ShowsActualDiff
30 mph31.1 mph+1.1
45 mph46.7 mph+1.7
60 mph62.3 mph+2.3
70 mph72.6 mph+2.6
80 mph83.0 mph+3.0

Gear ratio to match

CurrentEquivalent
3.423.55
3.553.68
3.733.87
4.104.25

305/55R20 is 1.20" taller than 305/50R20, a +3.75% change in diameter. That is more than the 3% many tire shops use as a limit, so plan on recalibrating the speedometer and checking ABS and stability control.

Ground clearance changes by 0.60" (half the diameter change), and the tire needs 0.60" more room above it.

Both tires are the same width, 12.01".

Both fit a 20" wheel; the sidewall is 0.60" taller on 305/55R20.

Details: 305/50R20 in inches · 305/55R20 in inches · change sizes in the calculator

FAQ

What is the difference between 305/50R20 and 305/55R20?

305/55R20 is 1.20" taller (+3.75%) and 0.00" wider than 305/50R20.

Will 305/55R20 change my speedometer?

Yes, by +3.75%. When the speedometer shows 60 mph you would be going 62.3 mph.

Can I replace 305/50R20 with 305/55R20?

It is a +3.8% diameter change, larger than the common 3% guideline, so check clearance and plan to recalibrate.