Cyclocross is a strange mix of off road riding and road cycling. Originating from Belgium the sport pre-dates mountain biking and was the original form of off road that riders used during the winter to keep themselves fit, improve strength and increase their bicycle handling skills. The races take place on off road circuits normally of around one mile in length that include a mixture of rough wooded sections, grass areas, technical sections, barriers that have to be run across and sharp slopes to be ridden or run up and then descended. This means that successful riders need to have great bike skills, aerobic endurance, explosive power and the ability to jump on and off the cycle without breaking their rhythm and run. Races last around an hour and are a true test of fitness and skill as anyone who has ridden narrow tyres off road can testify. The season lasts from September through to January which means that the bikers have to cope with all kinds of conditions through the winter from sun and dry ground to snow and ice.
Frames & Forks
Cyclo Cross bicycles look to the untrained eye just like a standard road bicycle. You might notice the nobbly tyres and the different brake systems, but with drop handlebars, 700c wheels and road components they are hard to differentiate.
The fames differ greatly from road versions with geometries that have shorter top tubes for a more upright and controlled position (similar to that on mountain bike). They have higher bottom brackets for clearance when hopping over obstacles and even greater clearance for the pedals from the rough terrain. Frames can be manufactured in a number of materials including steel, aluminium, carbon and titanium but in general they will be heavier than their road alternatives as they are made to be stiff and strong to cope with the high stresses that they have to withstand. The main triangle tends not to include water bottle cages as they interfere with the rider's ability to throw the bike over the shoulder when running. Top tubes also tend to be flat for comfort on the shoulder and the cabling is routed over the top of the top tube so that it cannot be caught on the cyclist or obstacles.
As with road bikes the forks are rigid and designed for the 700C wheels, however, they differ as they are designed to give increased clearance for wider tyres and mud. They are also designed to allow cantilever brakes to be fitted onto special bosses. Manufacturers produce forks in steel, aluminium and more commonly carbon. Full carbon forks are stiff, lightweight and can cope with the worst that the demanding sport of cross has to offer.
Cyclo Cross covers the whole season of weather conditions. In the early months when the ground is hard and dry riders favour fast rolling tyres with smoother tread to give them enough grip but allow them to utilise the fast conditions. A typical width of tyre for dry conditions ranges from 30-34mm. For wet and slippery conditions in the mud, tyres with extra grip are the preferred choice. With knobbly tread remaining narrow at around 30mm, the narrower the tyre the better it will cut through the mud. The air pressure in a tyre can be vital in order to cope with the conditions and can make a huge difference to the feel and performance of the bicycle. In the dry, higher pressures can be run (typically 65-75PSI) which will roll fast and provide enough grip with the firm ground. However, when the ground is wet the lower the pressure the more grip the tyre will have. The problem that can arise with normal clincher tyres (with a bead that is inflated by and inner tube onto the rim) is that running low pressures can cause the inner to be pinched and puncture. For this reason many who ride in cross races will prefer to use tubular or 'sew ups' as they are a self contained unit glued onto the rim and remove run the danger of pinch punctures. Many who use tubular tyres will run around 50 PSI when the ground is muddy. Tubes can also be ridden on without the tyre rolling, so if the rider does puncture the cycle can be ridden carefully back to the pits for a spare. It is worth spending time looking for the correct tyre and is a worthwhile investment as good quality rubber will perform well, last longer and is less likely to puncture. Above all, mechanical failures can affect the result in these gruelling races, so using the correct equipment is vital.
With the amount of running that is involved the preferred choice of pedals and shoes are those used for MTB riding. The pedals such as various SPD systems are good at shedding mud and can be clipped in from both sides which can be essential when jumping on and off the bike. The cleats are small and are recessed into the shoes amongst the tread on the bottom of the footwear so that they do not interfere when running. The shoes are designed with stiff soles that are still flexible enough to be run on with studs and have enough tread to give good grip when running on slippery ground and the steep slopes which are common place.
The gear ratios used on the bicycles tend to be easier than on the road in order to cope with the slower terrain and sharp slopes. Typically on a road bike the chainsets run 53/39 on the chainset and 12-25 on the cassette. However, cyclo cross bikes use compact sets typically using 48-36 and 12-27 on the cassette. This will depend on the nature of the course being ridden, but in general these ratios will provide enough range to cope with the challenging terrain that most courses are made up of. Apart from the gearing the gear systems are standard road components from the manufacturer's groupsets ranges from Campagnolo and Shimano. Ten speed is standard with these companies, but many who race cyclo cross still prefer to run older nine speed components as the wider spacing of the gears can be less prone to clog with mud. However the difference is so small that most are moving to ten speed.
Nearly all cyclo cross bikes will run cantilever brakes that work using a simple cable pulley system, although design can vary between manufacturers. They offer great clearance with their minimal look and can cope with the muddiest of conditions as they are designed not to clog up and slow the wheel. These brakes fit onto the bosses that come as standard on cross frames and forks. Some have started to investigate using hydraulic disc brakes as seen on MTB bicycles but the extra weight tends to override the undoubted stopping power and most still use cantilevers. On some designs cyclists use extra brake levers attached to the top of the bars that allow the rider to brake whilst on the tops of the bars. This can provide a lot more control and alternative hand positions, but most riders still prefer to use the standard STI levers.
Cyclo-Cross bicycles have a variety of uses aside from racing. The strong frame, easy gear ratios, standard road wheels and upright geometry make them ideal for winter riding, commuting and fast off road leisure riding. However, many race designed bikes will not come drilled with water bottle bosses for cages and bottles. In order to hydrate, the rider either needs to wear a hydration pack or drill bosses to accept the cages (please note this has to be done by a trained mechanic). Some lower end bicycles and frames will already have the bosses as the manufacturers recognise the various purposes that these bikes can be used for. Some companies even make sure that they drill the bikes to accept normal calliper brakes and include mudguard eyes so that they can be fitted with guards. Be warned that the very hard wearing and stiff nature of the frames can make them uncomfortable on long rides, with the differing geometries making them handle and feel very different to a standard bike. This varies greatly amongst manufacturers so be sure to check out the differing geometries of each frame to asses its suitability if you plan to use it for other purposes.