Okay, before anybody flies off the handle, I am not suggesting that you can do your own fit accurately enough without the help of a professional. So, with that in mind, use this as a way to either track your position or get in the “ballpark”. This is going to require a video recording app, white tape or sticky dots, video frame capture app, and an angle measuring app. First, I place the tape or dots on my hip at the joint of my femur, outside of my knee joint, and on the outside of my ankle. Then, I use the video ability of the iPhone camera app and record for 30 seconds – 1 minute and shift riding positions from the hoods/drops to aerobars. (You may need somebody to do this or a special rig) Next, I use an app like CatchFrame to get a snapshot of the video I took with my foot at the bottom of the pedal stroke. It is very important to NOT just take a photo of you sitting on your bike with your foot at the bottom. Your body must be in motion and warmed up, so take the frame from about 30 seconds in. Next, use an app like iGonio, vTrainer, or PhotoRuler, to import the photo you made and use their in app angle measurement tools to get your knee angle. Try to save this photo in a special album if you can to track your fit. Lastly, use a website like BikeDynamics to interpret your results and try their recommendations. I will also use a sharpie, black or silver, or tape to mark the position of bike parts once a good fit is found to see if anything moves after riding for a while. Again, this is NOT a replacement for getting a professional bike fitting.