Bike Fit Confusion

Question

A friend of mine has just purchased a 2016 Trek Emonda SL6 in a 54 cm frame size. He is 169cm tall and according to the Trek sizing chart (attached) he could fit a 52 cm or easily fit a 54. The trouble is with his saddle height set correctly (using a Gonimeter and verifying the result with the Bike Fast Fit app), his knee is 6 cm in front of the pedal spindle. If I move the saddle FULLY to the rear, and then get him to ride on a turbo trainer for 5 mins (to settle his position), his knee is still 35mm in front of the pedal spindle! This says to me that the frame is too small? I know that some say that we should not be too focused on KOPS, but I cannot get his knee inline or even behind the pedal spindle, either in during a static or dynamic fit? The seat post on the bike is standard and has a 20mm set back. I can replicate this 'fit' myself by sitting on my wife's medium sized Specialized Hybrid bike. I know this particular frame is far too small for me (I'm typically a Large or 58 frame), and with her saddle fully slid to the rear, my knee, when in the 3 o'clock position is approx 40mm in front of the pedal spindle. This is of course to be expected as the frame is too small for me, but why is my friends new Trek showing similar results? According to the Trek chart, the frame should/could potentially be too big for him? BTW, his cleat positioning is good. Please help!

Answer 1

Basing fit decisions on knee position relative to the pedals has largely been debunked as a myth. Furthermore, modern bike design trends have favored moving riders further forward on the frame and lowering the cockpit (i.e. handlebars) in order to put the rider in a more aerodynamic position. Trek's Emonda specifically was designed to be their most aggressive and responsive model; to achieve this, they use relatively steep tube angles that would make KOPS nearly impossible. This isn't a problem because they expect it to be set up and used with a 'racer fit'.

To see just how extreme this 'low and forward' position can be taken to, look at the setups of time trial and triathlon bikes. On mine, for example, the front of the saddle is essentially lined up with the bottom bracket. I've never considered knee position, but I think it's a safe assumption that it rests significantly forward of the pedal.