Those of you who think that most of the benefit comes when climbing or sprinting, are probably not pedalling very efficiently. If you are pedalling nice round circles, then you're significantly more efficient with clipless pedals. I don't think it can be answered in how many mph. It will depend on timeframe & what sort of speed you're trying to maintain. In a short burst, it may not be real significant. However, I am significantly faster over a longer period because I can employ different muscles. I've done simple tests with a heart rate monitor & varying how efficiently I pedal. Not real scientific, but when I change from just pushing on the downstroke to trying to pedal perfect circles, my speed will increase from 20 to 22mph while my "perceived effort" decreases. Heart rate, however, increases. This is due to the wattage that I'm producing has increased. The "perceived effort" has decreased because I'm employing more than just my quads to produce that wattage.



Personally, I'd probably be about 20mph slower with platforms since I've only ridden with them a handful of times in the last 17 years. The last time I did, I really had a hard time keeping my feet on the pedals.