Road Speed & Ratio Comparison Calculator
Road Speed & Ratio Comparison Calculator
Compare your current drivetrain setup to a new gear ratio or tire size. Instantly see the impact on road speed.
Built by Discount Parts Exchange — Ohio's Premier Heavy-Duty Drivetrain Rebuilder.
Current Setup
New / Proposed Setup
Results
Current Road Speed: 60.5 MPH
New Road Speed: 58.2 MPH
Difference: -2.3 MPH
Common Eaton Fuller Roadranger Top Gear Ratios
| Transmission Model | Top Gear Ratio |
|---|---|
| RTLO16713A | 0.73 |
| RTLO18913A | 0.73 |
| RTLO18918B | 0.73 |
| RTO16915-P | 0.79 |
| RTO16908LL | 0.74 |
| FRO16210C | 0.74 |
How Road Speed Is Calculated
Road Speed (MPH) = (Engine RPM × Tire Diameter in inches) ÷ (Axle Ratio × Transmission Top Gear Ratio × 336)
This is the standard formula used across the heavy-duty trucking industry for calculating road speed from RPM, tire size, axle ratio, and transmission overdrive.
Need help choosing the right ratio for your truck?