Here's an interesting article that at least attempts to link to some scientific sources claiming clipless has no efficientcy benefits. I'll continue to use clipless as that's what I'm used to but I do find some of the research enlightening. Maybe best answer is Lewis Morris & South (x Sourlands) no reason not to go clipless, anywhere North and at least give it some thought.
from
www.BikeJames.com
Clipless Pedal Myth #1: Clipless pedals let you pedal with more power.
Absolutely not true…there is nothing that shows that clipless pedals definitively let you produce more raw "power". In fact, some of the highest power outputs ever measured have been done on flat pedals (Nathan Rennie at the Australian Institute of Sport, for one). They do let you artificially strengthen the weak link of the feet which allows you to pedal longer before power starts to wane, which is useful for multi-hour/ multi-day racing, but there is absolutely no raw "power" advantage in clipless pedals. The fact that
you can't climb that steep hill without them is more in your head and lack of pedaling technique (see below).
Clipless Pedal Myth #2: You need to be able to pull up on your pedals to produce max power.
Again, this is simply not true no matter how many times it gets repeated. When studied, the most powerful and efficient method is not pulling up and producing power on the upstroke, it is instead driving hard with the lead leg and un-weighting the trail leg (Korff et al. Med Sci Sports Exerc 2007; 39:991-995). In fact, your pedal stroke with flats and with clipless pedals should remain exactly the same – there is no "magic" pedal stroke that is only available by attaching your feet to your pedals (Mornieux et al. Int J Sports
Med 2008; 29:817-822).
Clipless Pedal Myth #3: Your feet will bounce around and you'll have a hard time keeping them on the pedals.
Logically this makes no sense - some of the top downhill racers in the world run flats (World Champ Sam Hill among them) so obviously it is possible to go very fast through rough terrain and not have a foot bounce off. Two things make this possible, the first being 5:10 brand shoes with sticky rubber soles and some good flat pedals. That combination makes your feet feel attached like you were clipped in and will completely change how you view riding with flats. Second, being able to "ground" your feet into the pedals is a specific application of core strength that you have to learn and, once you do,
you won't feel like you feet are floating over your pedals anymore.
I think that a lot of riders are trapped by the paradigm that clipless pedals are somehow definitively superior when the facts tell us something much different. Just because most people come into mountain biking with dysfunctions that make it initially easier to use clipless pedals doesn't mean that they are better, or even good in the long run. In the hands of someone whose reality isn't shaped by the same dysfunctions, flat pedals allow you to ride every bit as hard and far; you just have to use a different technique that
isn't possible without addressing the core and hip weakness that are really at the root ofthe issue.
Let me close with this…in the hands of someone who isn't using them to mask
dysfunction clipless shoes and pedals are a useful tool. I just feel that they are competition level technology that isn't meant to be used everyday by your average rider. Flat pedals will enhance your technical skills and confidence, teach you better pedaling technique and save your knees, hips and low back – not a bad trade off if you can get past the "myths" surrounding clipless pedals.