When used correctly, panniers are a low hassle and secure system for transporting your gear on your bike. However, certain dangers come with the use of these bags, and you must be aware of them before installing a pannier to your bike. The primary threat is of the pack coming loose from your rack and falling into the road. This is a hazard not only to you, the biker but also to any pedestrians and vehicles that you are sharing the sidewalk or road with. A pannier falling off your bike is also likely to damage the contents of the bag. To stop this from happening, make sure the pannier is securely attached to your bike rack before setting out for the day. Also, routinely check the quality of the apparatuses used to attach the bag to the rack. These mechanisms do fail, mainly after they have been used for long periods. Keep up with the maintenance of your packs to avoid this danger.
The other danger presented by bike panniers are the bags warping and getting in the way of the pedals or wheel. Your bag hitting the pedals is a nuisance that makes riding unpleasant, but does not present any significant danger. However, a pannier getting caught in the spokes of the back wheel can arrest your bike, and can cause a bad crash. Many panniers come with inserts that keep them stiff and ensures that the bag will not get in the way. If you purchase a pack with this issue, it is also possible to make an insert. Another way to solve this problem is by filling the bag completely when you ride.
When installed correctly, panniers are perhaps the most straightforward system for carrying what you need on your bike. However, the above considerations show that even this great system can go array. Be careful whenever you get on your bike, pay attention if anything ever feels loose, and if you encounter any of these problems, make sure to remedy them right away.