1. What is a MPH RPM Gear Ratio Calculator?

Definition: This calculator estimates vehicle speed based on engine RPM, gear ratio, and a tire constant.

Purpose: It helps automotive enthusiasts and mechanics determine vehicle speed at specific RPMs for gear tuning and performance analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (miles per hour)
• \( RPM \) — Engine revolutions per minute
• \( GR \) — Gear ratio (unitless)
• \( C \) — Tire constant (accounts for tire size)

Explanation: The engine RPM is divided by the gear ratio to get wheel RPM, then multiplied by a constant that incorporates tire circumference to calculate speed.

3. Importance of Speed Calculation

Details: Accurate speed calculation helps in gear selection, performance tuning, and ensuring your vehicle operates within optimal RPM ranges.

4. Using the Calculator

Tips: Enter the engine RPM, gear ratio, and tire constant (default 0.002975 for typical passenger vehicles). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: How is the tire constant determined?
A: The constant is calculated as (60 * tire diameter in inches * π) / (63360 * GR). The default value assumes a 26" tire.

Q2: What's a typical gear ratio?
A: Final drive ratios typically range from 2.73 to 4.10 for passenger vehicles, with lower numbers for highway cruising and higher for acceleration.

Q3: Does this account for torque converter slip in automatics?
A: No, for automatic transmissions you may need to add 5-10% to the RPM to account for converter slip under load.

Q4: How accurate is this calculator?
A: It provides theoretical speed. Actual speed may vary due to tire wear, load, and transmission efficiency.

Q5: Can I use this for motorcycle calculations?
A: Yes, but you'll need to adjust the tire constant based on your motorcycle's tire size.