So I was wondering if any experienced persons had some ideas. Just got my new road bike with 700x23 tires. LBS sold me a Topeak odometer at cost to get rid of stuff for Trek Bikes(lost trek dealership). Anyway my buddy and I went for a ride today and it was my first trip out. We stopped for water at a point and I was mentioning out mileage. Mine said 9.63 miles and his was almost 12.5. I believe he has a cat eye odometer. His gps on his map my ride app was showing the same mileage as his odometer. I checked the settings and my computer was set to 2096C tires which is from what I can tell the correct setting. Any ideas? Thanks in advance