Topeak sells an allen key kit that weighs 68g if memory serves, called the Tool Bar.
http://www.sjscycles.co.uk/topeak-topeak-toolbar-compact-multi-function-tool-prod16114/ It's wonderful, well worth the money, don't leave the house without it. It forms the mainstay of my toolkit. In fact, with an 8x10mm spanner (wrench to you, Dan) for setting a Rohloff in gear after the cables break, that's an entire get you home kit for those of us with kevlar (etc) banded tires.
I'll tell you what I'd take in a toolkit to go around the world:
Topeak Tool Bar, 2.6 to 6mm hex bits, ali tyre levers, keyring
2mm Allen bit, fits Tool Bar, for Rohloff
8mm Allen bit, fits 6mm bit from Tool Bar, for crank bolts
T20 Torx bit, fits Tool Bar, for Robhloff
8mm hex socket to fit Tool Bar (from Xtools set
http://www.chainreactioncycles.com/Models.aspx?ModelID=10197 bought to get only that bit, rest in other toolkits)
Rohloff sprocket tool
Brooks saddle tension spanner, because it doesn't weigh much and anything else is just too fiddly to use
I would replace the only 10mm nut on my bike with 8mm and leave behind the 8x10mm spanner I now carry because the weight doesn't matter to me at present. (Park makes a lightweight 8x10mm flat steels spanner, if you'd rather.) I would also replace the 1/2in nuts on my Brooks B73 with fittings that can be operated by Allen key. Those with single rail Brooks saddles can replace the entire mounting with a Brompton Pentaclip, see
http://www.sjscycles.co.uk/brompton-penta-clip-for-rail-frame-saddles-qpentaclipa-prod13716/?src=froogleus¤cy=usdThat lot, which can all fit on a keyring, will dissemble my bike and repair the entire transmissionm including fitting a new chainring as I use Allen/torx ring bolts. No chain breaker is required if one uses quick links.
Topeak Peak DX, the only mini pump I know that works at all with big volume tyres.
Patch kit (the Topeak Tool Bar has two ali tyre levers on it)
2x spoke, rear
2x spoke, front
Good quality brake pads for the specific brakes fitted, in my case Magura rim hydraulics. (Not so sure I wouldn't prefer disc brakes for a world tour: the grit on roads in 2/3 of the world will grind through rims faster than I would be comfortable with.)
Rohloff service kit, for an emergency washout, presuming routine service kits have been sent to stops in advance.
Small tube of teflon grease, doubles as assembly grease, or marine grease if available in container so small, for regressing skewer tips and external small maintenance on the road. (No disassembly of major components is contemplated. Rohloff and Son hubs are not intended for users to disassemble, never mind beside the road, so they'd better deliver the reliability you pay for. The only other major assemblies, the headset and the bottom bracket, are "sealed" chuck and replace parts, not serviceable. If replacements are carried, the teflon will do for assembly grease.)
Assuming that I won't carry a bottom bracket or a spare chain ring, I'll assume that those who supply them along the way will also have relevant tools. If I carried a bottom bracket, I'd make it a Shimano tapered square type, because the tools for that fit securely without contortions with penny washers and duct tape and are light, which cannot be said for the Campagnolo tool required for my fave Kinex BB.
I could of course replace the Tool Bar with a torque wrench such as the BBB kit I keep in my toolkit at home, with again the additional bits, but I reckon that, if you are so inexperienced that you need a torque wrench not wreck the threads on a steel bike (nobody's going to try to go around the world on a plastic bike, are they?), you'd better wait a couple of years and a practice a bit.
Andre Jute
http://coolmainpress.com/BICYCLING.html