305/55R20 vs 35x12.50R20

35x12.50R20 is 1.8" taller than 305/55R20 (5.4%)

Diameter difference+5.39%diameter 33.21" → 35.00"
305/55R2035x12.50R20
305/55R2035x12.50R20Difference
Overall diameter33.21"35.00"+1.79"
Section width12.01"12.50"+0.49"
Sidewall height6.60"7.50"+0.90"
Circumference104.3"110.0"+5.6"
Revolutions per mile607576−31
Wheel diameter20"20"±0"

Speedometer

ShowsActualDiff
30 mph31.6 mph+1.6
45 mph47.4 mph+2.4
60 mph63.2 mph+3.2
70 mph73.8 mph+3.8
80 mph84.3 mph+4.3

Gear ratio to match

CurrentEquivalent
3.423.60
3.553.74
3.733.93
4.104.32

35x12.50R20 is 1.79" taller than 305/55R20, a +5.39% 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 0.90" (half the diameter change), and the tire needs 0.90" more room above it.

35x12.50R20 is 0.49" wider. On the same wheel offset about half of that, 0.25", moves toward the suspension and half toward the fender.

Both fit a 20" wheel; the sidewall is 0.90" taller on 35x12.50R20.

Details: 305/55R20 in inches · 35x12.50R20 in inches · change sizes in the calculator

FAQ

What is the difference between 305/55R20 and 35x12.50R20?

35x12.50R20 is 1.79" taller (+5.39%) and 0.49" wider than 305/55R20.

Will 35x12.50R20 change my speedometer?

Yes, by +5.39%. When the speedometer shows 60 mph you would be going 63.2 mph.

Can I replace 305/55R20 with 35x12.50R20?

It is a +5.4% diameter change, larger than the common 3% guideline, so check clearance and plan to recalibrate.