INTRODUCTION TO BICYCLES

Identification

A road bike is what most recreational cyclists, road racers and criterium racers use. Many new triathletes also use road bikes because they are easier to handle than triathlon bikes. Frequently, a new triathlete will put clip-on areobars on a road bike to improve aerodynamics. On a road bike, you position your hands on the brake hoods of the handlebars so your arms are perpendicular to the ground, with a slight bend in the elbows. 

Triathlon bikes are also known as time trial bikes. These are meant to be aerodynamic and are sometimes used in conjunction with aero helmets, shoe covers, and tight fitting clothing to decrease wind resistance. A triathlon bike has handlebars that are relatively flat and point out towards the front of the bike, and requires you to rest your forearms on the bars so your forearms are parallel to the ground.

Geometry

Triathlon bikes are built differently than road bikes, so that you use your quad muscles more and your hamstring muscles less than on a road bike. This can benefit triathletes because the hamstrings are necessary for running, so using your quad muscles more on the bike saves your hamstring strength for the run.

The seat tube angle on a road bike is usually around 73 degrees whereas on a triathlon bike it is usually 76 or 78 degrees, notes Bikesport, a Michigan specialty cycle store, which means that the angle between your thighs and torso is wider on a triathlon bike. This may make breathing easier on a triathlon bike than on a road bike that has clip-on aerobars. 

A road bike's geometry makes it better for climbing and for handling, which is why some people choose a road bike over a triathlon bike for a hilly triathlon course.

Speed

The most important factor for how fast your bike will go is how much you train. However, a triathlon bike can improve your speed without any additional training if the conditions are right. A road bike is going to faster under traditional road racing conditions, where handling and racing through corners are important. In a triathlon, you usually are not allowed to ride in close proximity to other riders, which makes a triathlon bike a faster choice.

Uses

Road bikes are preferable if you ride with a group frequently or race criteriums, because your hands are always positioned next to the brakes. A road bike is also better suited to long-distance cycling, as the upright position is more comfortable. 

A triathlon bike will make you faster than a road bike on the same course, provided you have been properly fit on your bike. A triathlon bike is the best choice for triathletes because its geometry makes it easier to run off the bike. A triathlon bike is also preferred for time trial cycling races, since time trials are usually on a course without a lot of turns and are seeded, so you never ride in a pack of other riders.

Frame Design

The UCI requires that road bikes posses a double triangle design. One triangle consisting of a top tube, down tube and seat tube and the second triangle consisting of a seat tube, seat stays, and chain stays. Triathlon bikes are not subject to these same regulations.

Wheels

Wheel choice varies by personal preference, type of race, terrain, and the rider's budget. However, triathlon bikes are typically equipped with deep dish wheels in order to improve aerodynamics and road bikes are typically equipped with lower profile wheels to decrease the overall weight of the bike.

Read more: http://www.livestrong.com/article/193083-tri-bikes-vs-road-bikes/#ixzz16kxsAnA3