Oh, I didn't realize that I was supposed to be going center but that makes sense for the asymmetry, thank you. As far as the lack of precision in results, I am beginning to suspect either my speed sensor accuracy or how the elemnt bolt uses the speed sensor. I have the elemnt set to use the wheel circumference instead of the "auto" setting which still uses some gps. However, my lap distances still vary by up to 26 feet in a set. What sensor do you use and/or is there a gold standard that people tend to use for aero testing? I've seen a lot of mentions for the gsc 10 but was having trouble getting my hands on one so I had settled for the garmin speed sensor 2.