In my last installment, I went over some of the technical aspects of flat pedals and shoe combinations and what to look for (and what to look out for) when riding said pedals and shoes. I also talked about some of the advantages that flat pedals offer the rider. In this installment, we'll talk “clip-in” pedals (otherwise called “clipless” pedals).
As I said last time, if you want to get the most out of your riding – become the most competent rider possible AND have the most fun – I highly suggest you learn to ride both types of pedals. Both have advantages and disadvantages and each one will teach you to really develop certain aspects of your riding that may not occur if you simply stick with one type of system. Neither is better or worse – especially when it comes to technically challenging (i.e.: FUN!!) riding.
It is often considered that the best way to ride a road bike – the most efficient way to pedal – is to “spin” very fast circles with the pedals, in a quite easy gear, and in theory, apply force throughout the entire pedal stroke (this was popularized by Lance Armstrong, among others), rather then “mash” the pedals, only applying force on the down-stroke (think standing up, pedaling, in a very hard gear). Its very possible to pedal like this (spin) on smooth surfaces, and I'm not going to argue that this isn't the best way to pedal a road bike or race a technically-easy cross-country race (although, there have been some very successful “mashers” on both the road and the dirt). Andy won't argue but the study linked to in this post does say that "spinning" is not as efficient as "mashing": http://betterride.net/?p=437
Because we will be pedaling at a slow cadence, we will be applying our power almost exclusively on the downstroke – even with clipless pedals – therefore, possibly (depending on who you talk to) negating any power advantage that clips may have over flats.
I personally feel that on extremely difficult, steep climbs, clipess pedals not only do not help the rider (because of the necessary slower pedal cadence) but also hinder the rider.
Advantages of clip-in pedals? First, the shoes are extremely stiff – stiffer then the shoes one would use for flats. This transfers more power to the pedal. Next, right under your foot and your super stiff shoe is a metal cleat which is engaged in a metal pedal. There isn't really any “give” in this system and the shoe doesn't “smush” down under your foot. I can usually feel this when I ride flat pedals and this is one of the only places where I can buy the argument that flats aren't as efficient as clips. Also, you can get your Lance Armstrong-spin going on flat, smooth sections of trail – but you can also do this pretty effectively with flats (?).
And one more advantage of clip-in pedals: just as flats force you to maintain excellent position on the bike in order to keep your feet on the pedals (and, thus, you're better able to control the bike), clips allow you get a little sloppy, and still, your feet are right where you left them, perfectly positioned on the pedals! This can lead to some bad habits if you start to rely on it, but it is nice at times!