My speedo registers a higher speed but is dead nuts accurate on distance. I used gaiagps to match it all up. Honestly, I don't much care about the speed. On the road, i'm either going slower than traffic or the speed of traffic. I guess I could beat a golf cart. In the dirt, well, sand, I don't use the speedo to judge what I should do, I use the seat of my pants. YMMV, of course.