At first glance, cyclocross and gravel bikes look similar: like road bikes with two 700c wheels, knobby tires and drop handlebars. But if you take a closer look and test ride a few of each type of bike, you’ll see and feel some important differences.
A bike’s geometry is what makes a bike fit and handle the way it does. Bike designers adjust important variables in frame geometry to give a bike a distinctive ride or feel. Gravel bikes are optimized for comfort over longer distances ridden on gravel and fire roads and sometimes even some smoother singletrack whereas ‘cross bikes are intended for short duration (<2 hour) high speed events around short cyclocross courses. Cyclocross bikes require high maneuverability around tight turns and over barriers and other obstacles, so their designers prioritize speed and agility over comfort.
A typical gravel bike will have longer chainstays, a longer wheelbase, a slacker head tube angle, a slacker seat tube angle and a lower bottom bracket than a typical cyclocross bike. Gravel bikes tend to have more mountain bike-like geometry while ‘cross bikes tend toward a racier, road bike geometry.
Every cyclocross course is unique, but most are between 2.5 and 3.5km long. On such short courses, there can only be so much change in elevation; hence riders need a narrower gear range. The pros, especially, can power up the quick, punchy climbs in bigger gears.
Gravel riders face much more varied terrain, including climbing and descending mountains, so do better to have wider gear ranges that let them spin up long climbs but not get spun out on descents or on fast flat group sections. Having the perfect gear is more important in combating fatigue over longer duration rides.
Modern gravel bikes comes with tire clearances of at least 40 mm. That means you can run relatively wider tires without fear of them rubbing against your frame or fork. Bigger tires mean more comfort while pedaling hour after hour over rugged gravel terrain.
Elite cross racers are limited in what width tires they can ride per UCI regulations to 33 mm; hence they have no need for large tire clearances. They need just enough room to accommodate the mud they’ll inevitably pick up during the wetter races.
Pure ‘cross bikes are for racing short distances so they come with few or no water bottle mounts and no eyelets for rack mounts whereas a gravel bike will typically have several water bottle mountains and the ability to easily attach racks to carry panniers and trunk racks. Gravel bikes often have simple, open frame designs to accommodate the mounting of frame bags of various shapes and sizes. Designers expect riders to take their gravel bikes out for long tours or bikepacking excursions.
On the other hand, ‘cross riders will be racing over short distances for a brief period of time, often in colder weather. They need little or no water while out on course, and they certainly don’t need to carry any gear.
Cyclocross is all about racing: every gram counts, and lighter is faster. Not only are ‘cross bikes subjected to being ridden in less rugged conditions for shorter periods of time, they must be light enough to be carried by their riders running up stairs and over barriers and other obstacles. ‘Cross bikes never have to carry racks and bags and other accessories, so pure ‘cross bikes are racing machines that use thinner and less robust tubesets, often made out of carbon or lightweight Aluminum. The opposite is true for gravel bikes; they are in general more robust and thus also heavier.
Not everyone has the time or space to have specialized bikes for each cycling discipline, so many manufacturers offer bikes that do double duty: good enough for some ‘cross racing and some gravel riding. Sure, there is always some compromising to be done when making a bike capable of multiple kinds of riding vs. being optimized for any single discipline, but with changes in bike technology over time – like the widespread adoption of disc brakes and 1x drivetrains, the differences between ‘cross and gravel bikes are becoming less and less over time.