A cyclocross bike is built a bit differently from a standard road bike, but the overall appearance is more chunky and usually there’s less of a height difference between the saddle and the bars. To ensure grip in off-road conditions, a cyclocross bike will be fitted with wide tyres.
Mud is almost inevitable in cross races and, to keep your bike rolling, cyclocross bikes are built with plenty of clearance between the tyres and the frame so that the wheels keep turning even when it collects on the bike during the race. This is evident around the forks, the chainstays and the seatstays and there’s also more space between the rear tyre and the seat tube and bottom bracket than on a road bike.
The more subtle difference from a road bike is in frame geometry. There’s typically a longer wheelbase for increased stability off-road and to build in the necessary clearances. The frame angles are slightly less acute which also helps with handling and there’s a shorter top tube. This results in a more upright riding position than on a road bike, which along with the more level bars and saddle allow the rider to shift their weight around more easily to tackle obstacles and to control traction.
Being robust, ruggedized and with lots of clearance and stability, cyclocross bikes are increasingly popular for other activities. They make good commuter bikes and many come with mounts for mudguards and racks, so that they can also be used as winter bikes or for touring.