275/60R20 vs 305/55R20: full comparison
| Measurement | 275/60R20 | 305/55R20 | Difference |
|---|---|---|---|
| Diameter | 32.99 in | 33.21 in | +0.22 in+0.7% |
| Section width | 10.83 in | 12.01 in | +1.18 in+10.9% |
| Sidewall height | 6.50 in | 6.60 in | +0.11 in+1.7% |
| Circumference | 103.65 in | 104.33 in | +0.68 in+0.7% |
| Revs per mile | 611 | 607 | −4−0.7% |
Speedometer: indicated vs actual speed
With 305/55R20 fitted where 275/60R20 was the stock/calibrated size:
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 20.1 mph | +0.1 mph |
| 30 mph | 30.2 mph | +0.2 mph |
| 40 mph | 40.3 mph | +0.3 mph |
| 50 mph | 50.3 mph | +0.3 mph |
| 55 mph | 55.4 mph | +0.4 mph |
| 60 mph | 60.4 mph | +0.4 mph |
| 65 mph | 65.4 mph | +0.4 mph |
| 70 mph | 70.5 mph | +0.5 mph |
| 75 mph | 75.5 mph | +0.5 mph |
| 80 mph | 80.5 mph | +0.5 mph |
Recalculate for a gear ratio change too →
Will 305/55R20 fit where 275/60R20 was?
At +0.7%, 305/55R20 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
- 275/60R20 vs 285/55R20
- 275/60R20 vs 33x12.50R20
- 33x12.50R20 vs 305/55R20
- 275/60R20 vs 295/60R20
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 305/55R20 than 275/60R20?
305/55R20 is 0.22 in taller in overall diameter (+0.7%) and 1.18 in wider in section width (+10.9%) than 275/60R20.
Will 305/55R20 fit in place of 275/60R20?
At +0.7%, 305/55R20 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 305/55R20 affect my speedometer?
With 305/55R20 fitted where 275/60R20 was calibrated, an indicated 60 mph is really about 60.4 mph. That small a difference is within the ±3% most shops treat as close enough not to recalibrate.
Does 305/55R20 change the ride height?
Yes -- half the diameter difference shows up at the axle, so 305/55R20 changes ride height by about 0.11 in higher compared with 275/60R20.
Do 275/60R20 and 305/55R20 use the same wheel (rim) diameter?
Yes -- both fit a 20 inch wheel, so only the tire itself changes, not the wheel.