How To: Build The Perfect Expedition Bike (Part 2)

(Just got here? Head over to Part 1 first.)

In Part 1 I went through some of the frame and suspension fork options available today for building up an expedition-worthy bike that will serve you well for long treks in remoter parts of the world. In Part 2 I’ll look at drivetrain options and other moving parts.

Gearing Systems

You might be forgiven for thinking that chains, cassettes, derailleurs and the like are all pretty much the same. Coming from a mountain-biking background, I’m perhaps biased, but there’s something to be said for higher-end mountain biking components: They’re build to withstand rather extreme forms of punishment.

I chose many components made by that popular fishing equipment manufacturer Shimano, because I heard that once you leave the West you’ll find that Shimano simply have the widest availability of any brand, and this proved true. Shimano have a bewildering array of expensive component series with funny names, as well as some seriously cheap and cheerful bits and pieces that can be found on spam-bikes at Tesco.

Several experienced Local Bike Shop owners and mechanics I’ve spoken to (i.e. those who know what they’re talking about), as well as a great array of other tourers, and the head honcho of Kona Europe, put their money on the Shimano XT series for the ultimate in durability and compatibility. It happens to be fairly affordable, relatively speaking — the initial outlay pays for itself in the long term. You don’t need the whole groupset — pick and mix.

LX, the next series down, uses cheaper and less durable materials in the construction of some moving parts of the derailleurs, and XTR’s hefty price step-up just shaves a few extra grams off for serious racers. But in all honesty, anything from plain and affordable Deore upwards should keep running for years with minimal maintentance. A big advantage of buying into this series is that almost all parts — spares, jocky wheels, chains, cassettes — are interchangeable with each other.

9-speed systems are almost ubiquitous these days, but I’d recommend looking out for 8-speed-compatible systems, shifters, chains, cassettes and rear derailleurs for which are still available new (in bits). Most Shimano rear derailleurs can be used with 8 or 9 speed shifters despite being branded as 9-speed, whereas for the front derailleur it makes no difference.

An 8-speed chain is slightly wider than a 9-speed one, and over time that adds up to a fair bit of extra strength and a lot of extra kilometres, but the main reason for choosing this is again compatibility — 9-speed parts are surprisingly hard to come by in the developing world. I use SRAM’s PC850 chains which have never caused me any problems.

Tip: Run your gear cable outers full-length from the shifter to the derailleurs, rather than using the frame’s cable guides. The less places for crud to get into your cable hoses, the longer they’ll last before corroding and freezing up.

Cranks & Bottom Brackets

I’d be tempted to break away from Shimano when it comes to cranks and bottom brackets. Shimano has barged in with a proprietary system called Octalink, which necessitates yet more specialist tools, and their products in this area don’t have the same reputation for reliability that their stalwart derailleurs have.

Ideally, I’d choose a standard square-taper bottom bracket — maybe from SKF, or Phil Wood, the Chris King of bottom brackets, if money were no object — plus whatever relatively light XC cranks I had lying around.

SKF also produce ISIS bottom brackets, which gives you access to a larger range of cranks and a supposedly more durable system overall, as square taper bottom brackets can be rounded off easily if improperly attached. I’ve been running my BXC600 for an impressive 20,000km. A miniscule amount of play has developed recently; we’ll see how it holds up this year.

Chains, Chainrings, Cassettes

Chainrings, chains and cassettes are the parts which directly receive whatever punishment you give them over the miles — direct metal on metal contact without regular cleaning leads to rapid deterioration. I usually take one spare chain and switch them every two weeks. Once each chain has done about 3,000km, I’ll replace it. Why? Chains stretch over time, and the stretch factor directly affects the rate of wear on the teeth of your chainrings and cassettes, as well as how often you clean the system. Easier and cheaper to replace chains fairly regularly than to have to replace the cassette and chainrings as well.

I’m using a special edition 8-speed Shimano XTR cassette which has several ultra-heavy-duty titanium sprockets. This 8-speed model isn’t in production any more, but you can pick up old stock on eBay. It’s done 20,000km with no visible wear — pretty astonishing. It also weighs considerably less than the cheaper 8-speed Shimano cassettes — but it’s not cheap.

My front chainrings consist of bog-standard steel granny and aluminium big rings, which are used far less than the middle ring. For this, I spent a bit more and went for a Middleburn hard-coated model. Again, it shows no discernable wear after a hell of a lot of pedal rotations. My cranks are standard-issue Raceface XC ones, which I pulled off a previously-butchered mountain bike before the trip began.

In total, I’ve used 5 chains, one set of chainrings, one cassette, one rear and one front derailleur, one set of shifters, one bottom bracket, and two sets of gear cables, with none of the above looking likely to need replacement any time soon. This remarkable record indicates that I probably chose well at the outset!

Tip: Clean and lubricate the chain and chainrings EVERY DAY. There is no substitute for this! 5 minutes a day running the chain through a rag, plus a few drops of the appropriate lube for the conditions, will extend the lives of these parts several times over.

That’s the bike — now for the luggage

Disclaimer: I’m not the world’s expert on bike building! This starting-point series is an abbreviated attempt to share everything I’ve read, learnt, heard and experienced about bikes over the last 4 years of planning and conducting long bike trips. There will be disagreements, which I welcome in the comments.

In Part 3 I’ll look at the rest of the stuff you need to finish off the bike itself, and Part 4 will look at the specific luggage-carrying requirements of a long expedition. Subscribe to the RSS feed or follow me on Twitter (I don’t spam) to make sure you don’t miss that, or any other future articles!