I have M540s, which are the same design as the 520s.. I put them on my fixed to try them out before I went to the track for the first time. Tightened up the tension as far as possible. It was great tooling around my street. Being able to pull up really helped acceleration and low speed stopping power was great. I was really excited, but then I went for a longer test ride around the block, and was going pretty fast down a mellow hill. A few blocks down I really had to stop fast because of some cars in front of me...my left foot popped out and the pedals kept spinning. Luckily I have a front brake or I would've been a new trunk emblem. That was the end of clipless for me, at least on my fixed bike anyway. They worked fine on the track though, but you don't skid or backpedal as hard there. I haven't used road pedals, but they might be different for fixed riding since most people seem to use them.