Bikes range in price from as little as $800 to well over $5000, and vary greatly in design, materials, and performance. If you are new to triathlon, or even contemplating a triathlon, do you have to have a tri bike?  If so what is the best tri bike for beginners?

To answer the first question you do not need a tri bike to participate in a triathlon, in fact it may be a bad idea to use one if you are new to the sport.  The best bike is going to be the one that you are comfortable and safe on.  I don't recommend making a decision on a new bike until you have participated in a a few races and have decided that you would like to advance in the sport of triathlon.

The first step in your purchase process is to choose between a road bike or triathlon specific bike.  If you like to participate in group rides, ride for fitness, charity events, and an occasional triathlon more than likely a road bike is going to be the better choice.  Many group rides frown on tri bikes as they are less safe: while in the aero bars you cannot quickly access the brakes which can jeopardize other riders safety.  If you want one bike that can do it all, and can only afford one bike, choose a road bike.

A tri bike is made specifically for triathlons and/or time trialing.  It has aero bars and a lower, more forward position, is slightly heavier than a road bike, and generally less comfortable. The tri position puts your center of gravity more forward over the front wheel and has your torso more parallel to the ground. The forward position is less stable and harder to handle compared to a road bike. Your hands are far from the brakes when in the aerobars, and the handling is twitchier and less controllable. I do not recommend this type of bike for most beginner triathletes. The purpose of the tri position is to cut aerodynamic drag, mainly by lowering your torso and creating a smaller profile.  But unless you are moving pretty quickly, the aerodynamics will not pay off much.  About 80% of the resistance while cycling comes from the air around you, but you must be moving above 20 mph to gain the full advantage. Air resistance increases with the cube of speed meaning the faster your go the more reducing aerodynamic drag matters.  If you are a slower cyclist the more aerodynamic position is not as much of an advantage, in fact the aero position is slower to climb in below 15 mph... I would start off with a road bike until you can sustain higher speeds and/or want to become more competitive.  

Once you have decided on what type of bike to buy the next question is which one?  This is really more about your budget and how competitive you are. An $800 road bike can actually be pretty reliable, but it will be heavier, require more maintenance and adjustment, and the parts will wear out faster. There is a trickle down in technology from top of the line road bikes, and an entry level bike can be of surprisingly good quality. Furthermore you can upgrade your bike over time to perform better, but you quickly arrive at a point of diminishing return in most cases.  An good example is switching to a better wheel set, which perhaps will have the biggest effect on increased speed and can be transferred to another bike.  Competition level bikes usually start with a mechanical Shimano 105 or SRAM Force component group or better, and proceed to fully electronic shifting. The less expensive component groups have a lot of the features of the more expensive groups but are generally heavier and less durable.  Campagnolo also makes excellent bicycle components, but they are usually found on more expensive European models. The differences between group sets are definitely there, but will not be as significant to the newer rider. If you are just getting into the sport, an entry level bike may be good enough for you. But if you think you are going to stick with it, ride consistently, and want to be competitive, you should spend the extra money.

Your best value can usually be found in an aluminum alloy frame, but carbon fiber has come way down in price. Aluminum is light, stiff, and relatively inexpensive compared with carbon fiber. Some complain that aluminum transmits road vibration more than other materials, but manufacturers have gotten much better in addressing this by shaping or "hydroforming" the tubing. Carbon fiber will dampen road vibration over long rides, and can be shaped and molded to more aerodynamic forms.  Carbon can be dramatically tuned to offer stiffness in key some places and lightness in others.  There are differences in geometry, or the purpose of the bike such as racing or touring. A more "traditional" or touring road geometry favors comfort and ride quality over handling and weight, whereas a racing geometry favors a lower torso angle, stiffness for power transfer, and the lightest weight possible.

New or used? Buying a new bike is like buying a new car. As soon as you drive it off the showroom you are out considerable money, but there is nothing like that new bike feel. If you are not handy, it is going to need regular maintenance (I recommend you learn the basics). Some shops offer a free lifetime adjustment policy; but this does not include maintenance and repairs. That being said, a full "tuning" or adjustment can run $40+ a pop. If you buy a used bike off of Ebay, Craigslist, or from an individual, you may get a lot more bike for the money or you may get a piece of junk. If you want to pair the price down, go used, but don't go cheap and inspect the bike carefully or have a professional do it for you. If you are not sure if you are going to stick with cycling this may be the way to go. Either way I highly recommend you get professionally sized, and that does not necessarily mean the sales guy at the shop eyeballing it for you. We use a process called "Biosize" which takes all of your biometric measurements to ensure you are on the right frame size. 

I believe the best values in bicycles usually come from the larger, mass produced manufacturers.  These companies have the R/D budgets to produce more cutting edge bikes, more sizes, and generally can be more cost competitive.  They are generally very high quality and offer the highest component level for the price. Think of them as the Hondas'. The European models generally have more "panache" with custom colors and even custom fitting. The Porsches' can run up to $8000 but are beautifully hand crafted works of art.  The fall is a great time to buy a bicycle as shops are clearing out the old models to make room for the next years and the Christmas rush, but beware- availability of a particular model or size can be limited. You are also going to need shoes, helmet, water bottle cages, computer, a good pump, flat kit, padded shorts, perhaps a rack, and tool kit. Be prepared, this is not a cheap sport even for the beginner, and there is an initial investment.  But a good bike offers many, many years of riding as long as it is maintained.