CHOOSING A BIKE - TECHNICAL GUIDE
DesignYou don't have to have a frame specifically designed for touring/expeditions but it helps.
The main features of a frame designed for touring are:
- thicker tubing to make the bike more suitable for load carrying;
- increased chain stay length to give more clearance between your heel and your panniers;
- wide clearance at the chainstays, seat stays and forks to allow for wide tyres and decent mudguards;
- threaded bosses or "braze-ons" on the seat stay, down tube and forks, for fitting front and rear racks and water bottles. (It is possible to fit racks and cages without these bosses, but it is a bit of a fiddle).
MaterialsFor touring bike frames, the choice is between steel and aluminium (you won't find anyone touring on carbon or titanium). There are some differences between the two materials: Firstly, steel is relatively easy to weld, so if your frame breaks in the middle of nowhere the local mechanic can at least have a go at repairing it. Aluminium is more difficult to weld and requires specialist kit. In general, aluminium frames are lighter than steel ones of equal strength, although this depends on the type of steel used. Aluminium has poorer fatigue properties than steel. Consequently, aluminium frames have to be a bit stiffer than steel ones to reduce the amount of flex - this is why the tubes tend to be of a larger diameter than steel ones. This can make the ride feel a bit harder. If you scratch your paint work, steel will rust but aluminium will just form a thin oxide layer and stop there. Aluminium is a little softer than steel, so it is easier to do damage like stripping the threads in rack mount bosses.
All things considered, by a small margin, steel is a better choice for an expedition bike than aluminium.
WheelsThe most frequent failures on touring bikes are wheels and racks. You can normally make running repairs to racks, but wheel failures can be serious. So, making sure your wheels are strong enough is a really important consideration for adventure touring. The factors that affect the strength and reliability of a cycle wheel are:
- its size
- the hub
- the quality/strength of the rim
- the number and quality of spokes
- how it is built.
SizeMTB style bikes are based on 26" wheels, whereas most road bikes are based on larger "700c" (approx 27") wheels. 26" wheels are generally stronger than 700c.
Another factor in favour of 26" wheels is that they are more widely available in the third world. It can be almost impossible to find replacement 700c wheels and tyres outside of Europe and North America. This is one of the reasons most top-end expedition bikes use 26" wheels. However, lots of people have completed very rough tours on heavily laden 700c bikes, so the whole wheel size thing is not that bigger deal.
HubsThe good news is that, provided they are of reasonable quality, e.g Shimano XT, and you clean and lubricate them about once a year, hubs rarely give you any problems. Hubs come in two flavours normal cup and cone bearings and ones where the bearings are contained in a cartridge. Cup and cones are a better option for touring as spares are much more readily available.
RimsThe choice of rim is important, particularly if you are going on a long trip or doing a lot of mileage on rough tracks. Good makes of rim include:
- Sun Ringle. The Sun "Rhyno" is probably the strongest rim on the market. However, it is also one of the heaviest.
- Mavic also make strong rims. However, I have heard more reports of cyclists suffering cracking with Mavic rims than any other brand. This may be down to people selecting the wrong rim for the job, e.g. the Ex721 model appears to be prone to cracking, whereas the CX717 seems OK. So check carefully that your Mavic rim is suitable for touring and the tyre pressure you are using is within spec for the rim.
- Rigida rims, e.g. Sputnik, X-plorer or ZAC 2000, are also quite popular for touring, perhaps better suited to roads than the rough stuff.
WearUnless you use disc brakes, all rims wear due to the abrasive action of the brake blocks. The rate of wear depends on the conditions and the type of brake block. In the dry, on flat tarmac and using soft brake blocks it can be a slow process and a rim may last 20,000+km. In the wet, on steep gravel tracks and with hard blocks it can be much more rapid. Having a rim fail due to wear on a high speed descent could more than ruin your day. You can detect rim wear by putting a straight edge across the rim and looking for a groove. More scientifically, most high end rims now come with some form of built in wear indicator that shows when the rim should be replaced. It can either be a dimple in the side-wall that eventually disappears or an inbedded line that appears when the rim has reached its wear limit. It would be daft of me to recommend riding on rims that have passed their wear limit, but you may be interested in our experiences. On our most recent trip, we fitted new Sun Rhyno rims before setting off. After just 2,000 km of cycling in the wet the rims had worn down to the indicators. This was a bit of a disappointment as we were planning another 7,000 km of pedalling. Without much of an alternative, we decided to chance it and continue riding. We had to shorten our trip due to other problems, but the rims performed flawlessly for another 4,500km, including 2,000km of very rough roads and tracks in Central Asia.
Spoke hole crackingThis is where tiny cracks form spreading out from the spoke hole. With continued use, the cracks become larger and propogate out from the hole. Eventually, either the spoke will pull through the hole or the rim fails completely. There is some debate about what causes this cracking. Over-tensioning of the spokes is almost certainly one factor. There is also some evidence that rims that have been "hard anodised" during the manufacturing process are more prone to this problem.
SpokesThe number of spokes is factor in the strength of wheel. Most touring/expedition bikes use 36 spoke rims. Some lighter touring bikes use 32 spoke wheels, but this is a little on the low side for carrying heavy loads. If you are planning on taking the kitchen sink with you, you can fit 48 spoke tandem wheels.
The strength of spoke depends on it's diameter and geometry. Spoke size is measured in "gauge" or mm. Confusingly, "gauge" decreases with increasing diameter. So a 16 gauge spoke is wider than a 18 gauge. For a stong trekking wheel 14 gauge (2.0mm diameter) spokes are best. In terms of geometery, the choices are:
- plain gauge - the diameter of the spoke is constant throughout it's length;
- single butted - the spokes are thicker at the hub end, tapering towards the rim end;
- double butted - the spokes are thicker at both ends than in the middle, e.g. 14 gauge at the end, 15 gauge in the middle.
Wheel BuildQuality of build makes a huge difference to the strength of a wheel. Wheels built by hand, by an experienced wheel builder, are much stronger and more durable than those built by machine (most wheels fitted to cheaper bikes will be machine built). So, if you are upgrading a bike for a big tour it's worth investing in a pair of really good handbuilt wheels.
TyresTyres have improved greatly in last few years. On our first tour, about 15 years ago, we had around 25 punctures in one month in South America. On our latest tour we suffered only one puncture in two months of cycling on very rough tracks in Central Asia.
Choice of tyre depends on the type of surface you are going to be riding on. For paved roads, you can get away with a relatively narrow tyre (28-30mm) and you don't want too much tread. Nobbly MTB tyres have quite a high rolling resistance are therefore unsuitable for long distances on tarmac. Off road, on rough tracks, you need a wider tyre 37+mm and a bit more tread.
Schawlbe currently make some of the best touring tyres around, including:
- Schwalbe Marathon - this is a good all round touring tyre, well suited to roads but able to cope with a bit of rough stuff too.
- Marathon XR - this is currently the tyre of choice for serious adventure cycling on mixed roads and tracks. It is very hard wearing (good for 15,000+km), has good traction and is available in a folding version, so it is easy to carry a spare. It probably has a little too much tread for 100% road use.
- Marathon Plus - this is a bombproof tyre which I have yet to puncture. It is quite a bit heavier than the other two and has a smoother tread than the XR.
Gear InchesOne of the ways gearing is measured is "Gear Inches". To calculate the gear inch for any one combination of cogs, take the diameter of your rear wheel in inches (including the tyre) multiply it by the number of teeth on the front cog and divide by the number of teeth on the rear cog. Thus, if you have a 35 tyre on a 700c wheel (27.1 inches) and your smallest cog on the front has 22 teeth, and you largest cog on the back has 34 - your lowest gearing will be 17.5 inches. For an expedition bike, you want a range of gears from around 17 to 90 gear inches.
Sheldon Brown has an on-line gear inch calculator at sheldonbrown.com/gears
GeneralIt's the range, rather than the total number of gears, that is important for touring. So, having 27 gears as opposed to 21, is no big deal. To gauge the gearing, count the number of teeth on the cogs on the front and rear rings. You need a very low gear (small cog on the front driving big one on the rear) for climbing up hill and a reasonably high one for racing down hill (big cog on the front driving a small one on the rear). A combination of three chainrings on the front with 22, 32 and 44 teeth, driving a set of rings on the back with a range of 11 to 32 or 34 teeth, will give a suitable range for expeditions into mountainous areas.
DerailleursI would guess 99.99% of bikes use derailleur gears and 99.99% of big tours have been done using derailleurs. The classic derailleur set up for touring is a crankset with three rings on the front, driving a cassette with seven or nine rings on the rear. Derailleurs are cheap (£20-50), reliable, easy to service (mechanics world wide know how to deal with them) and easy to replace. The main disadvantages of the derailleur system are that all the mechanism is exposed to dirt, grit and rain, the derailleur itself sticks out and can be knocked out of true, the width of cassette on the rear means the wheel has to have a lot of "dishing" i.e., unequal spoke length and tension to get the rim in the middle and within the 21 or 27 gears there's quite a lot of overlap.
Rohloff SpeedhubThe alternative to the derailleur is the Rohloff Speedhub. In effect, the Rohloff is a 14 speed gear box enclosed in an oversized hub on the rear wheel. It's a great bit of engineering. Gear changing is simpler (only one lever), smoother and you can do it when stationary, unlike with a derailleur. There's no derailleur sticking out, all the gearing is enclosed in an oil bath and the hub requires less dishing of the wheel. This lack of dishing is why the Speedhub only has 32 spoke holes -according to the company, without the dishing, it is as strong as a 40 spoke wheel. The Speedhub only has 14 gears, but this is OK because they are evenly spaced without the duplication of the derailleur system. People who have Rohloffs on their bikes rave about them and an increasing number of top-end expedition bikes now come with Rohloff hubs as standard. The downsides are that they are expensive (they add about £600 to the price of a bike), they require an oil-change every 5,000km, they need special drop-outs (so you can't just replace a Rohloff wheel with a normal one), they use extra-short non-standard spokes, minor maintenance (like replacing a cable) requires special tools and in the unlikely event they go wrong, you can't fix them in the field. I have yet to hear of a Rohloff failing completely, but I have heard of at least four instances of the flange breaking or cracking at a spoke hole. In each of these cases Rohloff has been very responsive in terms of getting a replacement hub sent out, but the cyclists concerned were still faced with the problem of re-building the wheel around the new hub.
PedalsPedal wise, you get to choose between plain ordinary flat pedals, pedals with toe clips (known as "rat-traps") and clipless pedals. With ordinary pedals, there's very little to go wrong, but they are less efficient and a bit less comfortable that alternatives.
Toeclips, or rat-traps, are pedals with cages and straps that hold the foot in the correct position and allow for a bit of power transfer on the up stroke. Using rattraps takes a bit of getting used to - if you forget to lossen the strap before you stop, you will fall over in a very uncool way.
With clipless pedals, you wear special shoes which have a cleat in the sole. The cleat clips into the special "clipless" pedals. When you want to stop you just turn your foot outwards and the clip releases (again, if you forget to release, you'll go over). The clipless system is more comfortable and more efficient again than rattraps. If you go for a clipless system it is important to choose one that is comfortable to walk in, i.e. with recessed cleats, such as Shimano SPD.
For a long tour rattraps are probably the best system, as you can wear any kind of shoes with them (from flip flops to trekking boots) and if the toe-clips fall to bits you are still left with working pedals.
ComponentsAfter the frame and the wheels, the quality of bike depends on the quality of the components. This includes things like the chainset(front cogs), the bottom-bracket, the front shifter, the rear derailleur, the rear cogs, etc. To be able to judge what is good and what is not so good, you need to develop a rather nerdy understanding of component brands and their relative merits. You can do this by reading bike magazines, visiting the component manufactures' webs sites and comparing bike specifications.
The market for bike parts is dominated by the Japanese company Shimano. The company makes a number of groups of components, or "groupsets", for mountain and road bikes. The rough hierachy of Shimano mountain bike groupsets (the ones most likely to be fitted to touring bikes) is:
2) Deore XT
3) Deore LX
So, for example, Deore XT components are better (lighter, more durable, smoother action) than Deore LX. However, it's not worth getting two hung up on the quality of components on a touring bike - as long as they work they are OK.
Campagnola and SunTour are the main alternatives to Shimano.
Rim BrakesThe vast majority of bikes use rim brakes. They are simple, easy to maintain and have all the stopping power you need for a touring bike. The limitations are that don't work so well in the wet and they eventually wear out the rims (see above). There are two main types of rim brakes used on touring bikes, Cantilevers and V-Brakes.
Older bikes tend to be fitted with Cantilever brakes. They are simple, reliable and work well, but are a bit more fiddly to set up than v-brakes. You should be able to find useable brake blocks almost anywhere.
"V" or Direct Pull Cantilevers do away with the transverse cable of traditional cantilevers. V brakes have more mechanical advantage and therefore more stopping power than cantilevers. They use thinner brake blocks than cantilevers, so you may find yourself having to carry more replacements on a long trips. V-brakes are also easier to set up than cantilevers. If you are upgrading your brakes from cantilevers to Vs, you will need to change or adapt your brake levers as they are not directly compatible.
Disc BrakesAn increasing number of mountain bikes and a few top-end expedition bikes are now being fitted with disc brakes. The main advantages of disc brakes are the significantly increased stopping power, better performance in the wet and no wear on the rim. However, for the expedition cyclist, these tend to be outweighed by the disadvantages that include the difficulty of fitting a front rack to forks with disc brakes, complicated setup, problems finding parts in developing countries, increased strain on the spokes, having to use a disc specific hub and the amount of dishing required in the front wheel.
Hydraulic BrakesHydraulic systems are now available for both rim and disc brakes. Hydraulics achieve better braking performance by eliminating the friction and stretch associated with cables and delivering more power to the pad. The downsides are they are difficult to set up, the hydraulic tubes are more prone to damage than their cable counter parts, they tend to go through pads quicker, parts are not readily available in developing countries and, if there is a problem, e.g fluid leak, they either work or don't work at all,
SuspensionHaving front fork suspension on a bike will make riding more comfortable on dodgy roads and rough tracks. The downside is that the suspension makes it a little more difficult to fit a front rack, adds to the weight and expense, and on long trips (3+ months), it is another thing to go wrong in the middle of nowhere. Coil spring forks are a better choice than pneumatic ones (no seals to blow) and it's a good idea to get forks with a lockout for road climbs. Good brand's include Fox's Vanilla RL, almost all Marzocchi forks Seat post suspension also makes for a more comfy ride on washboard tracks. It's relatively rare to see people touring on full suspension bikes, but it is doable. Both Tubus and Old Man Mountain make racks that are compatible with front and rear suspension.
SaddlesA few days into long tour is about the time you start to appreciate the importance of a decent saddle. The problem with buying a saddle, is that you really need to sit on it for 7 hours a day over a few days to know whether it is right for you. A very few bike shops will allow you to do this, before you buy.
Brooks leather saddles are probably the most popular with touring cyclists. They don't look particularly comfortable and have something of a reputation for a painful wearing in period, but most users swear by them. Rolls is another brand of leather saddle that has hand many good reviews.
HandlebarsFor long tours, it is important to have handlebars that have at least two positions for your hands. The main options are:
- Traditional racing bike style "drops". These have two, maybe three, hand positions, but in practice you rarely use the lower drops position when touring:
- MTB style straight bars. On their own these only have a single position, which rapidly becomes a strain on a long tour. Fitting a pair of bar ends, gives an alternative position and makes hill climbing easier.
- "Ergonomic" or "butterfly" bars. These have three hand positions and give a more upright riding position than drops. They are becoming increasingly popular for touring. The downsides are that it can be difficult to fit a bar-bag to butterflies (the click-fix may need an extender) and the foam covering rapidly gets tatty if you lean the bike up against walls.
Prop standWeight weanies will blanche at the thought of a prop-stand, but for the rest of us they are definitely worth it. Having a prop stand makes life on tour a whole lot more convenient. No more hunting around for a tree, crash barrier or wall to prop the bike against and less damage to panniers. Stands for fully loaded bikes need to be pretty beefy and are best fitted near the real axle. Hebie www.hebie.de make some good ones.
Cycle computersI am a recent convert to cycle computers. They are definitely worth having if only to keep a running total of how far you have pedalled.
LightsI have never felt the need for bike lights while on tour. You don't start pedalling until after sunrise and you normally stop well before sunset.
BellDuring a six-month trip I think I used my bell in anger about four times. They are however quite useful for getting your partner's attention and amusing local kids. More useful on cycle paths where you need to get round pedestrians. <
|Copyright © Tim Barnes 2007|