Sure, you rode a bike every day growing up. But in a triathlon you'll be dealing with gears, pedal stroke, riding in groups, taking corners, and navigating safely in traffic. Plus, you'll need to know how to fix a flat. (Don't worry, it's easy.Click here to learn how.)

In short, cycling for a triathlon is more complicated than tooling around the neighborhood. Here's what you need to know.

Buying a Bike. In your first triathlon, you've got a decision to make: be safe in your bike purchase or dive right in. Truth is, either way is fine since you're probably not posting Ironman times anyway. Take some time and decide whether you want to shell out more than $500 for a road or triathlon-specific bike or if you'd rather spend less upfront for a hybrid bike. Your hybrid will be a more relaxed ride, but will be slower. On the upside, if you decide triathlons aren't for you, you don't have a useless, expensive piece of metal in your garage. Click here for our picks of the best bikes from $500 to $5,000.

Fit Your Bike. Ideally, you're going to want your bike to feel like an extension of your body. With 3,000 to 5,500 revolutions on your pedals every hour, you'll want those two contact points as well as the other three-your two hands and your rear-to feel great. Follow these tips to set up your bike for a comfortable, injury-free ride. Adjust your bike fit if you start to feel discomfort. Even Lance Armstrong constantly fiddles with his bike. He listens to the experts but lets his body have the final word.

Spin. Literally. One of the most common novice mistakes is to mash through higher gears, hoping that will get you in shape faster. You're risking knee injuries and stalled progress. Watch any pro cyclist, they're always aiming to keep their legs spinning at a cadence of around 90 revolutions per minute. Let that be the guide to what gear you're in.

Pull on the Pedals. Pressing down with the balls of your feet is rough on your knees; you're place undue stress throughout your leg. Instead, practice pressing down with your heel and pull up with your calf, creating a more circular motion, says Ironman triathlete Steve Zambito. The extra practice this technique requires will pay off in generating power and speed more efficiently.

Put Safety First. Cycling is the fastest and longest leg of the triathlon. That makes it potentially the most dangerous. (We'll assume you've trained properly for the swimming portion.) If you're training on roads with cars, act like a safe car driver: pass on the left, follow lane markings, and signal stops and turns. Less obvious? Make eye contact with drivers. You'll ramp up their awareness of where you are.

Always (ALWAYS) Wear a Helmet. To that point, if you do crash, send in your helmet to the manufacturer to be checked out, even if it appears fine. Internal cracks happen and bring the helmet's effectiveness straight to zero. Besides, most manufacturers will replace a cracked helmet for free or with a nominal fee.