Mountain Bike chains break because of wear and tear,poor maintenance, and gear shifting under a heavy load. Others reasons are because of worn cogs, the chain gets hit, and chain suck. Lastly the teeth of the chaining is bent, not using proper joining pins, and not properly installing the bike chain.
How To Fix a Broken Mountain Bike Chain on the Trails
1.First thing you are going to need is a chain tool. It should be a multi tool and you should carry one with you anytime you will go riding out farther than walking distance from your home or car. So your chain is broken, hopefully only one link is broken. But sometimes depending on how your chain broke there may be more than one chain link that is twisted and not useful. No matter how many links are unusable you will need to remove them.
2.Take your chain tool and split the chain behind the broken links, so the broken links are not part of the chain anymore. Make sure the two ends of the chain are different so you can connect them. There should be one narrow end and one wide end.
3. On one of the ends there should be a pin, push this pin out of the chain, but not all the way out. Just until it is almost all the way out. It should be sticking out of the chain. Use the chain tool to do this. This pin will help to reconnect the chain and hold it together.
4. If you have a Shimamo rejoining pin it will make it easier to rejoin the chain.It's an extra part that just slides into the chain which holds it in place. You can easily slide the part in.
