You can ride a bike in just about any shoes you want but anyone who rides regularly can benefit from shoes designed specifically for bicycling. Shoes compatible with "clipless" pedal systems are a logical step up if you seek greater cycling ease and efficiency.
The added benefit from increased power that the cyclist achieves from wearing cycling specific shoes is immeasurable. With the engineered design of cycling shoes, through the incorporation of a rigid sole and breathable fabrics, a cyclist will acquire increased speed and power in addition to comfort by wearing these cycling specific shoes.
There are multiple different varieties of cycling shoes. These are specific to each type of cycling that the rider is participating in. These include touring, mountain biking, spin class and racing.
Touring or Casual Shoes
Touring or Casual shoes are built for comfort and often, if a cleat is installed, it is very minimal to allow for walking. An emerging category is the so-called hybrid cycling/casual footwear. These look like casual shoes (or even sandals) and allow easy walking, but their soles offer compatibility with clipless pedal systems. This versatile style is a great option for the casual rider or bike commuter.
Mountain Biking Shoes
Mountain biking shoes have a cleat that is designed to allow for the cyclist to quickly clip out of the pedal when on unstable terrain. Spin class shoes have a slightly less rigid sole and offer increase breathability for comfort during an indoor spinning class. Finally, racing shoes are designed for the speed and to be lightweight and breathable.
These shoes have a fairly stiff sole for efficient pedaling, but one with enough flex and a rubber-lug outsole to allow good traction for walking on slick or rugged rails. They offer a lacing or hook-and-loop strap system (such as Velcro® brand closures) to adjust the fit of the shoe and offer a bit of protection for your toes.
As you move up in price, you get features such as stiffer soles, lighter weight, enhanced foot and/or ankle protection, waterproof liners, additional hook-and-loop straps or a buckle-and-ratchet-type strap for an improved fit and foot security. Some shoes also offer removable toe spikes for the ultimate in traction when dismounting your bike.
Clipless mountain-bike shoes use the 2-hole cleat system, described below, so you'll want to match it up with a compatible pedal. Check the "specs" tab on REI.com product pages to make sure the shoes you are considering can mount the proper clipless cleat.
Some mountain bike shoes have a flat sole and cannot mount cleats. These styles are meant specifically for use with platform pedals (and optional toe clips).
Road Cycling Shoes
Road-biking shoes are distinguished by their exceptionally stiff soles to facilitate power transfer to your pedals. Road shoes and cleats are not designed for extended walking and therefore do not have much in the way of traction on the sole. They are uncomfortable to walk in over longer distances due to their inability to flex. This is a performance feature and is done to create the most efficient power transfer possible while on the bike.
Virtually all road shoes offer lightweight construction and good ventilation. As you look at higher-priced models, materials such as carbon fiber are used to further increase sole rigidity and fit systems allow greater customization. On many styles, a small rubber pad on the heel provides the only traction.
Most clipless road-bike shoes use either a 3-hole or 2-hole cleat system,described below, so you'll want to match it up with a compatible pedal. Check the "specs" tab on REI.com product pages to make sure the shoes you are considering can mount the proper clipless pedal. (Note: Some Speedplay and Time models use a 4-hole cleat system.)
One notable road-cycling niche is triathlon-specific footwear. "Tri shoes" are built for race performance with maximum energy transfer and simplified foot entry/exit for transitions on and off your bike.