My mountain bike hydration pack is full on long rides, not just with water. In addition to the usual multi tool, spare tube, first aid kit, jacket and patch kit these items can make a ride ending mishap a minor inconvenience.
1. A head lamp (w/fresh batteries), when someone is injured or you have a mechanical darkness can come fast. A head lamp was one thing sorry missed when a friend got severely injured last year. Having a light would of helped us care for him and signal help when they finally arrived around 10 pm (he wrecked around 5 pm).
2. Your cell phone! Just because you friend is carrying his doesn’t mean you don’t need yours. Where our friend wrecked AT&T phones had no reception but Verizon did (my Verizon however was in my car). Having my phone would of gotten help there hours earlier.
3. Food, three tasty, calorie pack Tram Bars and a GU with caffeine to get me home! Spending the night outdoors and/or carrying a friend back is exhausting, some extra food can really help.
4. A shock pump, if your shock or fork runs out of air this can make getting home a lot more fun.
5. A lighter! It was fall when our friend was injured and having a lighter allowed us to start a fire. This kept all of us warm and helped the rescue team find us.
6. Duct tape! If duct tape can’t fix it it ain’t broke! From helping boot a mountain bike tire to taping a broken frame together (to limb it home) duct tape can be a big help. (Notice I wrapped a bunch around my tire pump)
7. Money! Money can buy you a tube, bribe someone for a ride, buy food and a dollar bill can be used to “boot” a small slice in your tire sidewall.
8. A Fedex or Priority Mail envelope. Ever notice how tough these are?! Great for booting a big slice in a sidewall or combining with duct tape to hold something together.
9. A real chain breaker instead of the one on your multi-tool. Much easier to use and a much better success rate.
10. A leather-man tool! From holding loose bolts to sawing your arm off (see the movie 128 hours) nothing beats a leather-man.
11. Chain lube, stream crossings, rain and mud can make your bike unrideable. A small bottle of chain lube can save you.
12. A derailleur hanger for your current bike (that old derailleur hanger won’t help you).
13. A cloth for cleaning your glasses or chain
This is by no means everything you may need. Always bring more water and clothing than you think you will need on long mtb rides.