Allen keys
Allen keys
This one’s a given. Pretty much any multi-tool ever made will have some form of Allen key on it. They’re the delight and bane of the cycling world. They make adjustments super easy on the go but, as anyone who’s ever tried to remove a stripped Allen bolt will know, they can be a nightmare when they wear out.
Obviously all bikes are different but, in general, a tool with 2, 3, 4, 5, 6 and 8mm attachments will see you through most predicaments with ease. But, as ever, make sure you check what your bike has because you don’t want to end up not having the right key for that one odd-sized bolt.
To be honest, if you had to drop one the 8mm could go. It’s on there because lots of pedals screw in with an 8mm allen key, and it makes removal easy (although getting the required amount of force with such a small lever can be difficult). But the odds are you won’t need to remove your pedals on a standard ride, so if you have to sacrifice one, the 8mm might be it.
Elsewhere, the stem, topcap, seatpost, derailleur mounts and crank spider all use Allen bolts, so you’ve got all those covered. Unless, of course, they happen to use torx bolts…