275/55R20 vs 285/55R20: full comparison
| Measurement | 275/55R20 | 285/55R20 | Difference |
|---|---|---|---|
| Diameter | 31.91 in | 32.34 in | +0.43 in+1.4% |
| Section width | 10.83 in | 11.22 in | +0.39 in+3.6% |
| Sidewall height | 5.95 in | 6.17 in | +0.22 in+3.6% |
| Circumference | 100.25 in | 101.61 in | +1.36 in+1.4% |
| Revs per mile | 632 | 624 | −8−1.3% |
Speedometer: indicated vs actual speed
With 285/55R20 fitted where 275/55R20 was the stock/calibrated size:
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 20.3 mph | +0.3 mph |
| 30 mph | 30.4 mph | +0.4 mph |
| 40 mph | 40.5 mph | +0.5 mph |
| 50 mph | 50.7 mph | +0.7 mph |
| 55 mph | 55.7 mph | +0.7 mph |
| 60 mph | 60.8 mph | +0.8 mph |
| 65 mph | 65.9 mph | +0.9 mph |
| 70 mph | 71.0 mph | +1.0 mph |
| 75 mph | 76.0 mph | +1.0 mph |
| 80 mph | 81.1 mph | +1.1 mph |
Recalculate for a gear ratio change too →
Will 285/55R20 fit where 275/55R20 was?
At +1.4%, 285/55R20 is within the ±3% most tire shops and manufacturers accept without recalibrating the speedometer or expecting rubbing -- it should generally bolt on, though wheel width, offset, and suspension travel still matter.
Related tire size comparisons
- 275/55R20 vs 275/60R20
- 275/55R20 vs 275/65R20
- 275/60R20 vs 285/55R20
- 275/55R20 vs 33x12.50R20
- 265/60R20 vs 275/55R20
More tire tools
- Tire size comparison tool: compare any two sizes yourself, including flotation sizes.
- Tire size calculator: full dimensions of one size, plus every equivalent size within 3%.
- Speedometer calculator: true speed after a tire or gear ratio change.
Frequently asked questions
How much bigger is 285/55R20 than 275/55R20?
285/55R20 is 0.43 in taller in overall diameter (+1.4%) and 0.39 in wider in section width (+3.6%) than 275/55R20.
Will 285/55R20 fit in place of 275/55R20?
At +1.4%, 285/55R20 is within the ±3% most tire shops and manufacturers accept without recalibrating the speedometer or expecting rubbing -- it should generally bolt on, though wheel width, offset, and suspension travel still matter.
Does swapping to 285/55R20 affect my speedometer?
With 285/55R20 fitted where 275/55R20 was calibrated, an indicated 60 mph is really about 60.8 mph. That small a difference is within the ±3% most shops treat as close enough not to recalibrate.
Does 285/55R20 change the ride height?
Yes -- half the diameter difference shows up at the axle, so 285/55R20 changes ride height by about 0.22 in higher compared with 275/55R20.
Do 275/55R20 and 285/55R20 use the same wheel (rim) diameter?
Yes -- both fit a 20 inch wheel, so only the tire itself changes, not the wheel.