285/70R17 vs 285/55R20 Tire Comparison
285/70R17 has nominal diameter 32.7087 in; 285/55R20 has 32.3425 in. Diameter changes -1.119%; at indicated 60 mph the new nominal speed is 59.328 mph. Selected standard passenger and common truck/SUV tire sizes, not a verified market-popularity ranking. Nominal dimensions do not guarantee vehicle fitment.
285/70R17 vs 285/55R20 Tire Comparison reference last updated · reference source
Loading calculator…
Dated static reference; no live data is fetched. Verify current source values and assumptions before relying on results.
What this tool does
285/70R17 has nominal diameter 32.7087 in; 285/55R20 has 32.3425 in. Diameter changes -1.119%; at indicated 60 mph the new nominal speed is 59.328 mph. Selected standard passenger and common truck/SUV tire sizes, not a verified market-popularity ranking. Nominal dimensions do not guarantee vehicle fitment.
How to use the 285/70R17 vs 285/55R20 Tire Comparison
- Check Tire width (mm): 285.
- Check Tire aspect ratio (%): 70.
- Check Tire rim diameter (inches): 17.
- Check Tire B width (mm): 285.
- Check Tire B aspect ratio (%): 55.
- Check Tire B rim diameter (inches): 20.
- Check Indicated speed (mph): 60.
- Review the 285/70R17 vs 285/55R20 Tire Comparison result and its exact-value comparison table.
- Verify assumptions before applying the result.
Formula
difference%=(diameterB/diameterA−1)×100; actual speed=indicated speed×diameterB/diameterA
- width
- Tire width (mm)
- aspect
- Tire aspect ratio (%)
- rim
- Tire rim diameter (inches)
- widthB
- Tire B width (mm)
- aspectB
- Tire B aspect ratio (%)
- rimB
- Tire B rim diameter (inches)
- speed
- Indicated speed (mph)
Assumes the speedometer was calibrated to the original tire. Does not check wheel offset, width or clearance.
Worked example
285/70R17 vs 285/55R20 Tire Comparison: Tire width (mm) = 285; Tire aspect ratio (%) = 70; Tire rim diameter (inches) = 17; Tire B width (mm) = 285; Tire B aspect ratio (%) = 55; Tire B rim diameter (inches) = 20; Indicated speed (mph) = 60. 285/70R17 has nominal diameter 32.7087 in; 285/55R20 has 32.3425 in. Diameter changes -1.119%; at indicated 60 mph the new nominal speed is 59.328 mph. Selected standard passenger and common truck/SUV tire sizes, not a verified market-popularity ranking. Nominal dimensions do not guarantee vehicle fitment.
Inputs
- Tire width (mm)285
- Tire aspect ratio (%)70
- Tire rim diameter (inches)17
- Tire B width (mm)285
- Tire B aspect ratio (%)55
- Tire B rim diameter (inches)20
- Indicated speed (mph)60
Result
- Diameter difference (%)-1.12
- Actual speed (mph)59.33
- Ground clearance change-0.18 in
285/70R17 versus 285/55R20
| Measurement | Original tire | New tire |
|---|---|---|
| Diameter (in) | 32.70866141732284 | 32.34251968503937 |
| Sidewall (in) | 7.854330708661418 | 6.171259842519685 |
| Circumference (in) | 102.75729041741734 | 101.60702224110295 |
| Revolutions/mile | 616.5985862669311 | 623.5789476208964 |
| Speed at indicated 30 mph | 30 | 29.66417910447761 |
| Speed at indicated 45 mph | 45 | 44.49626865671642 |
| Speed at indicated 60 mph | 60 | 59.32835820895522 |
| Speed at indicated 70 mph | 70 | 69.21641791044776 |
Results explained
- Diameter difference (%)
- Diameter difference (%) from the formula above. Assumes the speedometer was calibrated to the original tire. Does not check wheel offset, width or clearance.
- Actual speed (mph)
- Actual speed (mph) from the formula above. Assumes the speedometer was calibrated to the original tire. Does not check wheel offset, width or clearance.
- Ground clearance change
- Ground clearance change from the formula above, expressed in in before metric conversion. Assumes the speedometer was calibrated to the original tire. Does not check wheel offset, width or clearance.
Frequently asked questions
Diameter difference is -0.3661 inches (-1.119%).
7.8543 and 6.1713 inches respectively.
Nominal actual speed becomes 59.328 mph if calibrated to 285/70R17.
616.60 versus 623.58 geometric revolutions/mile.
This comparison cannot confirm fitment. Ground clearance changes -0.1830708661417333 in geometrically; verify wheel width, offsets, load/speed ratings and manufacturer requirements.