1. What is the PPM Calculation?

The PPM (Pulses Per Mile) calculation determines how many pulses a vehicle's speed sensor generates per mile traveled. This is crucial for accurate speedometer and odometer readings, especially after modifications to tires or gearing.

2. How Does the Calculator Work?

The calculator uses the PPM equation:

Where:

• \( 63360 \) — Inches in one mile
• \( \pi \) — Mathematical constant Pi (~3.14159)
• \( \text{Tire Diameter} \) — Diameter of tire in inches
• \( \text{Axle Ratio} \) — Vehicle's axle ratio
• \( \text{Teeth} \) — Number of teeth on the speed sensor reluctor wheel

Explanation: The equation calculates how many times the speed sensor will pulse based on the tire's circumference, final drive ratio, and sensor teeth count.

3. Importance of PPM Calculation

Details: Accurate PPM values are essential when changing tire sizes or gearing to maintain proper speedometer accuracy and proper operation of vehicle systems that rely on speed signals.

4. Using the Calculator

Tips: Measure your tire diameter accurately (or use manufacturer specs), know your axle ratio (found in vehicle specifications), and count the teeth on your speed sensor gear.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire diameter?
A: Measure from the ground to the top of the tire (loaded) and multiply by 2, or calculate using tire size markings.

Q2: What if I have metric tire sizes?
A: Convert metric sizes to inches (e.g., 265/75R16: (265×0.75×2)/25.4 + 16 = total diameter in inches).

Q3: Where can I find my axle ratio?
A: Check your vehicle's specifications, door jamb sticker, or sometimes the axle itself has markings.

Q4: Why does PPM matter for modified vehicles?
A: Larger tires or changed gearing will affect speed readings unless the vehicle's computer is reprogrammed with the correct PPM.

Q5: Can this be used for kilometers?
A: For km, replace 63360 with 100000 (cm per km) and the result will be pulses per kilometer.