Tire Ruler305/55R20 dimensions
| Overall diameter (height) | 33.21″ · 844 mm |
| Section width | 12.01″ · 305 mm |
| Sidewall height | 6.60″ · 168 mm |
| Wheel diameter | 20″ |
| Rim width (rule of thumb) | 8.5–10.5″ |
| Circumference | 104.3″ |
| Revolutions per mile | 607 |
| In inches (flotation style) | 33.2 × 12.0R20 |
How it’s calculated: the sidewall is 55% of the 305 mm width = 167.8 mm (6.60″). Add two sidewalls to the 20″ wheel: 20 + 2 × 6.60 = 33.21″.
Bigger tires than 305/55R20 on 20″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 285/60R20 | 33.5″ | +0.26″ (+0.8%) | 60.5 mph |
| 265/65R20 | 33.6″ | +0.35″ (+1.1%) | 60.6 mph |
| 295/60R20 | 33.9″ | +0.73″ (+2.2%) | 61.3 mph |
| 34x11.50R20 | 34.0″ | +0.79″ (+2.4%) | 61.4 mph |
| 275/65R20 | 34.1″ | +0.87″ (+2.6%) | 61.6 mph |
“60 mph reads” is your real speed when a speedometer set up for 305/55R20 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Sizes equivalent to 305/55R20
Within 1.5% of the same height on a 20″ wheel. Usually interchangeable for the speedometer; check width, load index and clearance.
| Size | Height | Width | Difference |
|---|---|---|---|
| 33x12.50R20 | 33.0″ | 12.5″ | −0.6% |
| 275/60R20 | 33.0″ | 10.8″ | −0.7% |
| 285/60R20 | 33.5″ | 11.2″ | +0.8% |
| 265/65R20 | 33.6″ | 10.4″ | +1.1% |
| 295/55R20 | 32.8″ | 11.6″ | −1.3% |
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 33x12.50R15: 33.0″ tall on a 15″ wheel (−0.6%)
- 285/75R16: 32.8″ tall on a 16″ wheel (−1.1%)
- 295/70R17: 33.3″ tall on a 17″ wheel (+0.2%)
- 255/80R17: 33.1″ tall on a 17″ wheel (−0.4%)
- 33x12.50R17: 33.0″ tall on a 17″ wheel (−0.6%)
- 275/70R18: 33.2″ tall on an 18″ wheel (−0.2%)
- 33x12.50R18: 33.0″ tall on an 18″ wheel (−0.6%)
- 305/45R22: 32.8″ tall on a 22″ wheel (−1.2%)
- 275/50R22: 32.8″ tall on a 22″ wheel (−1.1%)
- 33x12.50R22: 33.0″ tall on a 22″ wheel (−0.6%)
Popular 305/55R20 comparisons
Frequently asked questions
Is 305/55R20 a 33 inch tire?
Yes. 305/55R20 is 33.21 inches tall, so it's sold and talked about as a 33-inch tire.
What size is 305/55R20 in inches?
305/55R20 is 33.2 inches tall (overall diameter), 12.0 inches wide, with a 6.6 inch sidewall, and fits a 20 inch wheel.
What tire size is equivalent to 305/55R20?
Sizes within 1.5% of the same diameter on a 20" wheel: 33x12.50R20 (33.0"), 275/60R20 (33.0"), 285/60R20 (33.5"), 265/65R20 (33.6"). Check load index and width before swapping.
What rim width fits 305/55R20?
As a rule of thumb, about 8.5–10.5 inches. The tire maker's spec sheet lists the approved range for each model.
How many revolutions per mile does 305/55R20 make?
About 607 revolutions per mile in theory (circumference 104.3 in). Real tires turn slightly more because they flatten under load.