How do you calibrate VW vanagon speedo?

To calibrate the speedometer on a VW Vanagon, you need to determine the correct tire size and ensure it matches the speedometer's expectations. Start by measuring the actual speed using a GPS device or a speedometer app while driving at a consistent speed. If there's a discrepancy between the GPS speed and the speedometer reading, you can adjust the speedometer by changing the speedometer gear or using a correction factor if available. Finally, retest to ensure accuracy after making adjustments.