245/40R18 vs 245/45R18 Tire Comparison
245/40R18 has nominal diameter 25.7165 in; 245/45R18 has 26.6811 in. Diameter changes 3.751%; at indicated 60 mph the new nominal speed is 62.250 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 245/45R18 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; 245/45R18 has 26.6811 in. Diameter changes 3.751%; at indicated 60 mph the new nominal speed is 62.250 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 245/45R18 Tire Comparison
- Check Tire width (mm): 245.
- Check Tire aspect ratio (%): 40.
- Check Tire rim diameter (inches): 18.
- Check Tire B width (mm): 245.
- Check Tire B aspect ratio (%): 45.
- Check Tire B rim diameter (inches): 18.
- Check Indicated speed (mph): 60.
- Review the 245/40R18 vs 245/45R18 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 245/45R18 Tire Comparison: Tire width (mm) = 245; Tire aspect ratio (%) = 40; Tire rim diameter (inches) = 18; Tire B width (mm) = 245; Tire B aspect ratio (%) = 45; Tire B rim diameter (inches) = 18; Indicated speed (mph) = 60. 245/40R18 has nominal diameter 25.7165 in; 245/45R18 has 26.6811 in. Diameter changes 3.751%; at indicated 60 mph the new nominal speed is 62.250 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)245
- Tire B aspect ratio (%)45
- Tire B rim diameter (inches)18
- Indicated speed (mph)60
Result
- Diameter difference (%)3.75
- Actual speed (mph)62.25
- Ground clearance change0.48 in
245/40R18 versus 245/45R18
| Measurement | Original tire | New tire |
|---|---|---|
| Diameter (in) | 25.716535433070867 | 26.681102362204726 |
| Sidewall (in) | 3.8582677165354333 | 4.340551181102362 |
| Circumference (in) | 80.79087879231705 | 83.82115517077965 |
| Revolutions/mile | 784.2469465256681 | 755.8950943936348 |
| Speed at indicated 30 mph | 30 | 31.125229638701775 |
| Speed at indicated 45 mph | 45 | 46.68784445805266 |
| Speed at indicated 60 mph | 60 | 62.25045927740355 |
| Speed at indicated 70 mph | 70 | 72.62553582363748 |
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 0.9646 inches (3.751%).
3.8583 and 4.3406 inches respectively.
Nominal actual speed becomes 62.250 mph if calibrated to 245/40R18.
784.25 versus 755.90 geometric revolutions/mile.
This comparison cannot confirm fitment. Ground clearance changes 0.4822834645669296 in geometrically; verify wheel width, offsets, load/speed ratings and manufacturer requirements.