245/40R18 vs 275/55R20 Tire Comparison
245/40R18 has nominal diameter 25.7165 in; 275/55R20 has 31.9094 in. Diameter changes 24.081%; at indicated 60 mph the new nominal speed is 74.449 mph. Selected standard passenger and common truck/SUV tire sizes, not a verified market-popularity ranking. Nominal dimensions do not guarantee vehicle fitment.
245/40R18 vs 275/55R20 Tire Comparison reference last updated · reference source
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Dated static reference; no live data is fetched. Verify current source values and assumptions before relying on results.
What this tool does
245/40R18 has nominal diameter 25.7165 in; 275/55R20 has 31.9094 in. Diameter changes 24.081%; at indicated 60 mph the new nominal speed is 74.449 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 245/40R18 vs 275/55R20 Tire Comparison
- Check Tire width (mm): 245.
- Check Tire aspect ratio (%): 40.
- Check Tire rim diameter (inches): 18.
- Check Tire B width (mm): 275.
- Check Tire B aspect ratio (%): 55.
- Check Tire B rim diameter (inches): 20.
- Check Indicated speed (mph): 60.
- Review the 245/40R18 vs 275/55R20 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
245/40R18 vs 275/55R20 Tire Comparison: Tire width (mm) = 245; Tire aspect ratio (%) = 40; Tire rim diameter (inches) = 18; Tire B width (mm) = 275; Tire B aspect ratio (%) = 55; Tire B rim diameter (inches) = 20; Indicated speed (mph) = 60. 245/40R18 has nominal diameter 25.7165 in; 275/55R20 has 31.9094 in. Diameter changes 24.081%; at indicated 60 mph the new nominal speed is 74.449 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)245
- Tire aspect ratio (%)40
- Tire rim diameter (inches)18
- Tire B width (mm)275
- Tire B aspect ratio (%)55
- Tire B rim diameter (inches)20
- Indicated speed (mph)60
Result
- Diameter difference (%)24.08
- Actual speed (mph)74.45
- Ground clearance change3.1 in
245/40R18 versus 275/55R20
| Measurement | Original tire | New tire |
|---|---|---|
| Diameter (in) | 25.716535433070867 | 31.909448818897637 |
| Sidewall (in) | 3.8582677165354333 | 5.954724409448819 |
| Circumference (in) | 80.79087879231705 | 100.24648998954832 |
| Revolutions/mile | 784.2469465256681 | 632.0420795441905 |
| Speed at indicated 30 mph | 30 | 37.22443355786895 |
| Speed at indicated 45 mph | 45 | 55.83665033680342 |
| Speed at indicated 60 mph | 60 | 74.4488671157379 |
| Speed at indicated 70 mph | 70 | 86.85701163502755 |
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 6.1929 inches (24.081%).
3.8583 and 5.9547 inches respectively.
Nominal actual speed becomes 74.449 mph if calibrated to 245/40R18.
784.25 versus 632.04 geometric revolutions/mile.
This comparison cannot confirm fitment. Ground clearance changes 3.096456692913385 in geometrically; verify wheel width, offsets, load/speed ratings and manufacturer requirements.