Here is the disclaimer for aspiring triathletes about to start the process of picking out a bicycle for their training and the race: do not attempt on your own. Unless you are already familiar with road bikes, you don't know enough to begin to make an intelligent choice. Get professional help at your local bike shop.
Start with this principle: the cycle you will ride in the race is nothing like the old bike you got as a kid — the lumbering, clunky machine that you braked by pushing back on the pedals. Race cycles are light and sleek with hand brakes and gears that you actually use.
For triathlon newbies, the best choice might be to borrow a road bike for the training and the race. A new entry-level road bike will cost about $700, and you can spend many thousands for state-of-the-art machines. It would be smart to delay investing in a fancy road bike until you are sure you want to continue doing triathlons.
You could ride an old-fashioned bicycle in a triathlon. It would be within the rules. Without gears to help you up and down hills, however, you would finish the ride with dead legs and nothing left for the run. Don't even think about taking a “lead sled” to a triathlon.
If you have a friend with a road bike, ask if you can borrow it. If the bike is available, it would be worth your while to take it to a bike shop and have the staff check out the cycle to make sure it will be functional for your training and the race.
If you do not have access to a loaner bike, consider purchasing a used one. Your local bike shop might have some on hand, or they might know where you could find a good used machine.
You could probably find a used bike at a reasonable price on eBay, but there is a potentially major downside to doing so. It is very important that your bicycle fits you, which requires in-person inspection with the assistance of an expert. You can't get that if your bike has to be shipped to you. There is more about how to make your bike fit later in this chapter.