If you thought picking running shoes was tough, picking the right cycling shoes can boggle the mind. Size is important – too big and your foot will slosh around and you will have a tough time getting the proper lift on the back of the pedal stroke. Too tight, well shoes that are too small just plain hurt. This ain’t hockey (hockey players typically cram their feet into skates that are 1-3 sizes too small). My road shoes, which I won, were delivered a half-size bigger than advertised so I do have a bit too much room, but they’re close enough that I don’t have too many problems. On the other hand, my mountain biking shoes are too small unless I wear thin socks. When I replace them, I’ll definitely choose a pair a full size larger. My current shoes were picked at the bike shop by one of my favorite mechanics too… I share this only as a caution for noobs – cycling shoes should be snug, not tight.
Beyond that, there are a couple of other things to consider. I used to have the same SPD mountain biking pedals on my mountain and road bikes so I could use the same shoes on both bikes. This presented a huge problem on road rides longer than 30 miles or so because of two differences between mountain and road shoes. First, road shoes have soles that are much stiffer than your middle-of-the-road mountain biking shoe. A stiffer shoe helps transfer more power to the pedals; they’re more efficient. Also, SPD cleats are smaller than most road cleats (especially the Look cleats and pedals that I now have) – so what ends up happening, when you put a small cleat on a more flexible sole and try to ride hard over a long distance, is the part of your foot above the cleat goes numb or starts to hurt. I rode through it and never developed problems that lasted more than twenty minutes after getting off of the bike, though the discomfort could definitely be tough for some to deal with.
Composite Vs. Plastic
I own carbon road/triathlon shoes and plastic mountain shoes. I used the mountain pedals on my road bike for a year before I upgraded to real shoes, pedals and cleats and I can tell you with utter certainty, while I still have work, I will never go back to plastic mountain shoes on my road bike.
With the cleat protected by lugs on the sole of the mountain shoe, I love being able to walk in my shoes without having to carry special cleat covers in my back pocket. On the other hand, my road pedals (Look KEO Classics) are half the weight and offer several times the surface area connecting the foot to the pedal – this means that on long rides, 50-125 miles, my feet don’t develop hot (sore) spots.
Now the next question to tackle is tricky: Did I notice a difference between the road and mountain pedals in terms of “power to the pedals”? Well I was a serious noob back when I switched over – I hardly knew how to throw an index adjustment on my rear derailleur so I simply wasn’t capable of distinguishing a difference. I’ll leave that answer to all of the other pros in the industry who say there’s a difference. Once my feet stopped hurting on long rides I stopped caring about anything else because riding without unnecessary pain over the long haul is the name of the game.