How to start traveling the world by bicycle?

There are many bike resources on the web. I recommend https://bicycles.stackexchange.com/, eg.

Find the organizations in your country that focus on bicycle touring. In the US that’s Adventure Cycling Association.

And just ride. Scrape together some gear and do some long day rides, then some overnighters. While you’re doing that, work on getting the right gear, starting with a good, sturdy bike with a good gear range and decent brakes. Fancy is not required — you don’t need disk brakes (though it’s OK to have them), and an old-fashioned steel frame is preferred to aluminum or titanium or carbon fiber. You do need good tires (fairly wide for a road bike) and you need to know how to fix them.

As others have said, start small. That’s good advice. You won’t realize how badly untrained hands and arms can feel after a relatively short ride (not to mention good saddles your butt might not be accustomed to…).

The next bit is comfortability on the bike itself — and this really means understanding what you like, not what The Right Formula has to say about your body. I’ve ridden a BSO (seriously, $120, fully-rigid MTB type, with my own $30 saddle) over 8,000 miles and loved it, and ridden a $6,000 “dream bike” less than 200km before deciding it was destined for the trash. I would have preferred to tour on the BSO MTB than the expensive bike. But this will usually not be the case. In any circumstance, though, you should ride whatever you intend to tour on several thousand miles before setting out, unless you’re rich and can afford to replace gear until something happens to fit just right.

(I destroyed the BSO frame in a spectacular crash where it was ridden, literally, into the ground and I wound up unhurt — whew!; and the amazing $6,000 pile of technology was traded to a rich guy who likes bikes,)

Once you get used to commuting distances (I mean > 40km a day or so, and this implies you’ve already done the climb through 5km/day to 40km day — which is its own adventure, but one which is easily researched) in your own town then you should start riding to unfamiliar towns to find out what it feels like to ride every day somewhere you don’t know. This matters a lot more than you might think at first,

The last bit, and the part I think that is most often overlooked, is the idea of learning how to become comfortable living in the open when necessary. I could probably ride from Fukuoka to Sapporo sleeping in a family hotel every night without any issue (Japan is well settled), but I would be hard pressed to do so in the US or Canada (where inhabited regions can be separated by vast spans of literal wilderness). And that brings up another point: self defense. I’m not going to get into this here, as quite a few cyclists hold extreme emotional investments in one side or the other of the concept of violence, but it is something you should contemplate if you plan on actually circumventing the landspace of the globe on a bicycle. Along with self defense comes the other issues of living alone in the open: you need practice.

Camping, cooking, cleaning, staying healthy, not getting depressed (which, when alone, really boils down to genuinely understanding who you are), not getting manic, getting enough sleep, not falling into a state of unmanaged sloth, not feeling like crap every day, not carrying too much weight, not carrying too little gear, carrying too much cash, not having access to enough cash, etc. are little things that will really bite you once your body is physically adjusted.

Anyway, have fun. Take everything everyone here has to say with a grain of salt (especially if they are touting particular gear or price ranges). You’re the only one who will know when you’re ready.

This may sound a bit a too phylosophical answer for such practical questions, but it’s all about what you want and your will.

Of course being in shape helps, of course having a more expensive / light bike helps but not allways.

Except for being in shape every advantage you may have may turn to be a disadvantage in one or another situation. (Eg.: If you buy an expesive bike you will be afraid of leaving it alone. If you take too much weight it will be nice (more amenities) but the effort to carry stuff will be higher.)

The fact that you’re worried is a good sign but don’t overthink. Do a reasonable plan (try to think of what to do if things don’t go according to expectation). But the experience will come with the travel itself.

You don’t need to be a professional biker to bike 100Km a day. Preparation is important, but you can also start slow. Do less kms each day, and increase as you go alon in your trip.

Take these guys example: http://ateondevaiscom1000euros.blogspot.nl/ – it’s in Portuguese (Gtranslate helps). They did more than 2500Km with 50Euros bikes (From Portugal to Dakar). Their total budget for their trip was 1000euros (indluding bikes).

First of all it’s about your inspiration and your will!

For an overview of practical aspects give a look at this answer. I compiled a few in this answer.

how to start:
Start small. Don’t think you can cycle long distances without getting in shape. Even across town may well be a challenge for you right now.
So start on that, set yourself REALISTIC goals to get in shape, not just your legs but your arms and lungs as well.
Start with say 10km trips, then gradually increase that until you can comfortably drive the distance you think your average day’s leg will be in a reasonable amount of time (wouldn’t do to plan a 200km trip a day and find yourself exhausted after driving 100km in 8 hours for example).
Don’t think you can exist on energy drinks and granola bars alone. Yes, they make great energy boosts but they’re not exactly healthy as your sole or main source of food.

What bike:
WAY too broad to answer. Would depend heavily on the routes you plan to take. But overall, you probably want one that’s rugged, relatively light to drive, and is easy to repair BY YOU in the field with whatever’s available from the local blacksmith shoppe. Especially in rural areas (and many third world countries) you shouldn’t expect to find well equipped bicycle repair shops with high tech parts and the ability to repair that carbon-carbon frame you just broke driving over a dirt filled pothole. A steel pipe frame is a lot easier to maintain, but of course heavier.

Again, set yourself realistic targets. Don’t plan a round the world trip as your first major adventure.
Instead plan a trip to the next province for a long weekend, or a week to the next country over.Few hundred kilometers to get a taste, and close enough you can catch a train back in a few hours if things go horribly wrong.
Gradually widen that. Maybe a year later drive a thousand kilometers over a week or so, year after that make it 2000 in a month (yes, as you get further from home things slow down, your support network becomes smaller and slimmer, etc.).

And then you get the biggest problem: visa, invites (which you need for many countries), travel restrictions, finding places to stay, healthcare, etc. etc..
It’s not for nothing that such endeavours are often undertaken by larger teams with a home support crew handling stuff like that, which can sometimes take months to get the permissions for a country you just have to cross because your travel plans just changed (natural disasters, wars, etc.).

OK, you’re at the stage where you have a ton of questions. I’m in a similar position about long distance walking actually, but that’s a different story for another time.

Firstly, I should probably plug our Bicycles.Stackexchange.com site. For the actual bicycle questions part of your trip, they’re going to be a handy resource.

One of the biggest cycling communities online is Warmshowers.org. Funny name, but it’s like couchsurfing for cyclists. When I was in Central Asia, I met a lot of long distance cyclists, going from Europe to China or back, and many of them had used it or were hosts. It’s a community for meeting other cyclists on the road, who might just meet you for a coffee, or host you for a couple of nights, give you a place to stay and.. obviously, a warm shower (hence the name).

As the site tends to attract a lot of people with very similar questions to those you have, they’ve set up a forum, with blogs and stories, bikes for sale, questions from first timers, concerns, experiences and more. It’d also be a great place for finding people doing similar trips and meeting up and potentially cycling with them!

Hope that helps. I’m not a big cyclist, but those I hear from nearly always recommend this site.

Oh, almost forgot. A friend of mine cycled for 20 months from London, UK to Christchurch, New Zealand. Here’s her blog – note it’s in reverse order. Gives a bit of an insight into the stuff you have to deal with.