Choosing a bike
So you've decided you want to do a bike tour, now you need a bike. Here's a guide to try to help you decide what you need.
26" or 700c wheels?
Where are you planning to ride? In general 26" wheel are a bit stronger and it's easier to pick up spare inner tubes and tyres in countries where bike shops are few and far between. However, 700c are slightly more comfortable and better at absorbing bumps. They often come on lighter bikes/road bikes so may be a better option if you will mostly be riding on road. I chose 26" mountain bike wheels for my trip, because of the long off-road sections I did. If I was going to ride across America (for example) on roads, I would probably chose a bike with 700c wheels. 27.5 and 29er wheels are also great but it is more difficult to get spare tyres for these in remote parts of the world.
Steel or aluminium?
For me steel is a perfect for touring. Shock-absorbing, easy to weld if something goes wrong and the "classic" touring bike frame material. Having said that, unless you're planing a long tour with off-road sections, an aluminium frame will be fine and probably slightly lighter. I'd always go steel though, if you have the choice.
There's loads of options. I had standard mountain bike handlebars, with bar ends, which meant I could change my hand position quite a lot. My friend Harry, rode across America with me on drop handlebars, which gave him lots of options. Curved "butterfly" style handlebars are also popular, but not all gear/brake levers will fit onto them. Whatever is comfortable for you is best. I found road-bike handlebar tape is more comfortable than grips.
This depends on what you can mount on your bike frame/wheels. If your bike can take disc brakes, I thoroughly recommend hydraulic disc brakes. Their reliability is worth every penny, and in any case, they're pretty cheap these days. I used basic shimano ones and had absolutely no problems for my entire trip. Just make sure you can change the pads and try not to damage the hydraulic hoses. If not, any rim brake is fine, although I'd stay away from hydraulic rim brakes for touring.
Easy - Schwalbe Marathon Plus Tour. No contest. On or offroad, they're incredible. Mine have lasted over 10,000 miles and are still pretty puncture resistant.
Again, easy... Ortlieb...
Tubus. Get a Disco on the rear if you have discs and a Smarti on the front if you don't have mid-fork mounts. Lots of other options for almost any type of bike. Check out their website
Brooks are great, but can be a bit annoying in the wet. On the whole though, they're probably the best choice. I used a Specialized Body Geometry one, which was very comfortable though.
If you have enough money, a Rohloff speedhub is a no-brainer. It's the perfect gear system for touring. The only other geared hub I know people have used is the Alfine, but it's not in the same league. Otherwise standard gears are fine, shimano deore or SLX is probably enough for MTBs and sora/105 for road. I wouldn't spend a fortune on XT/XTR/Ultegra... because you're paying for weight saving that you don't need to worry about (a pannier weighs a lot more than any bike component)
I would definitely recommend using SPDs. I got a set of £20 shimano spd pedals and they got me all the way around the world. Just take a spare pair of cleats. The ability to be able to pull up on the pedal make a massive difference and you get used to twisting your foot out of the clips very quickly. Toe clips are another option but in my opinion are not as good. Flat pedals are fine but you're losing out on a lot of extra pedalling power.