Not all aluminum bike frames are created equal. T6 grade aluminum which is used in airplanes offers stronger frames due to its heat treatment process prior to welding. Other grades do not go through the heat treatment process, creating a weaker aluminum alloy. Choose a frame from the T6 class, commonly listed as 6061 aluminum alloy. Giant's Defy 2 road bike received high marks as did the Marin Argenta. Both weigh in around 21 pounds, a respectable lighter weight for an aluminum road bike.
Bikes manufactureres will often put together the same frame with different grades of components, such as wheels, shifters, gear rings and cranks. Choose the best frame you can buy, even if you get lesser grade components. These parts can all be upgraded in the future.
Where to Buy
Aluminum road bikes have hit the mainstream in the sporting goods stores. Independent bike stores offer a greater variety with brand and models. Check the parts if you find a model offered by both. Traditionally, the department stores offer versions with cheaper components than bike stores carry. Buyers often believe they are buying the exact same bike, when they are not.
A low end aluminum road bike will start around $400 and up. For a good T6 frame, expect to start a bit higher, in the $800 range. The Marin Argenta, one of the better aluminum bikes on the market, runs $1,400. Giant's Defy 2 enters the market at $1,100. Shop in the fall for best pricing.
Remember to look for the 6061 or T6 aluminum grade for a better quality aluminum frame. Lesser grades, such as 7005 and 7200, will still provide a nice ride.
Do not forget a helmet. Verify that the bike comes with pedals. Higher-end bikes often do not.
Stop by an independent bike store. Many of them offer computerized scanning to perfect your bike fit. Often this service can be worth the extra $100 you would pay to buy the bike from them. Some will fit any bike, even those purchased elsewhere, for a fee.