A good hydration pack needs to be comfortable to wear. It should fit well to avoid chafing and shifting around on the trail. It should also have a secure, durable design to handle the bumps and scrapes of the trail. A quality sternum strap and hip belt helps stabilize the pack. And, it should have enough room to store non-liquid cargo such as spares and extra layers.
Hydration packs designed for mountain biking are often larger to give riders the space they need for tools, gear and food. They are usually more durable to deal with the rough terrain and less streamlined for better aerodynamics.
The capacity of the hydration bladder is another important consideration. Standard sizes like 2.5 liters are great for most rides and can easily be topped off at gas stations or water fountains along the route. If you’re going to be riding for hours you’ll want a bigger bladder, such as the 15 liter capacity of the Source Summit mountain bike hydration backpack.
To reduce sweating and the potential for back chafing, look for a pack that has air channels that run through the load-bearing zone of the pack to vent heat and keep your back cool. Also, consider a pack with a bite valve shutoff switch and hose portals that clip to the shoulder straps so the hose doesn’t flop about while you ride. Many hydration packs also offer options to trim the hose length or position it on one side of the pack versus the other.