PDR Speed/lap times
 

A couple of questions on the PDR system if anyone can help.
Is the speed the same as the speedometer or is it based on the GPS. The reason I'm asking is I went to 18 inch wheels and the speedo is no longer accurate so I'm not sure if the speed on the PDR is accurate or just taking it from the speedometer.
Also will the different wheel size affect the lap time calculation? I went out today and turned in what I thought were some great lap times but when I compared it to my previous laps with the stock size wheels I ran the same lap time.. When I played back the video of both sessions I was much faster on the straights and corners today than in the prior session but the lap time was the same. Very Strange !

The PDR speed channel is based off wheel speed. Lap time is triggered off GPS data. If you have Pi Toolbox you can create a math channel for speed from the GPS data.

What size tires are you running. If you are running Hoosier 345/35/18 rear tires the speedo should be close enough that you shouldn't really notice a difference. The stock tire diameter is 26.6 inches and the 345/35/18 Hoosier diameter is 26.8. If you went with the Hoosier 335/25/20 tire your speedo would be less accurate since its diameter is 27.1 inches.

Bill