You've seen people hooking a water bottle cage to the frames of their bikes -- but are they really worth the trouble? There's no doubt that having something to drink while you're on a long ride is necessary, but you have a number of options for storing those drinks. When it comes to knowing whether you "should" have a water bottle cage on your bike, the answer is really up to you, your riding habits and your ability to ride one-handed while drinking from a bottle.
Naturally, the biggest pro of having a water bottle cage is having easy access to hydration. Putting the cage on your bike means you won't have to worry about carrying your water bottle anywhere else. If you're the type who doesn't like wearing anything on your back while riding, the cage frees you up and can keep you from getting a wet, sweaty back from lugging around a backpack. Most bikes are built with small holes in the frame for installing a cage, so installation usually takes just a few minutes.
Relying on a water bottle cage to carry all of the water you need for your workout does have its cons. According to the American Council on Exercise, you should be drinking about 17 to 20 ounces of water in the two to three hours before you work out, another 8 ounces 20 to 30 minutes before the workout, and then 7 to 10 ounces every 10 to 20 minutes during your workout. Water bottle cages typically hold bottles up to 20 ounces in size, so depending on the length of your ride, one cage may not hold enough water for the ride. Plus, if you're expected to drink every 10 to 20 minutes, that means a lot of time leaning down or stopping on the bike to grab your bottle -- which can be difficult on tough terrain. It is possible to install two cages to cut down on the first problem, but for the second problem, you may want to consider another alternative.
You have a couple alternatives to having a water bottle cage: one is to strap a water bottle to a chest harness or bottle holder, where it will be more easy to reach. The other is to use a hydration pack, basically a backpack with a water bladder and drinking straw. This option makes it easier to take a sip when you need one without having to lean down to grab the bottle, but for that reason the bladders are harder to clean and are not recommended for use with any other liquid besides water. On the plus side, though, hydration packs can carry upwards of 100 ounces of water -- much more than the bottles stored in your cage.
If you're on your mountain bike for an hour or more, you're going to need more than just water to help replenish your electrolytes and help keep you going. That's when a combination of the hydration pack and the water bottle cage can come in handy. Your hydration pack can provide you the water you need for the ride, while your water bottle cage can hold a sports drink that you can use when you need a little pick-me-up.