Gravel Bikes vs. Road Bikes: What's the Difference?
Gravel and road bikes are similar enough that it can be hard to know which one is the right bike for you. Cycling Expert Mikael Hanson details the main differences!
If you step back and think about it, gravel bikes are not new. In fact, they’ve been around in some form or fashion for decades. But as the world of endurance sports grows, so do the many disciplines within each sport, and they’re all seeking a special piece of equipment for optimal performance and enjoyment for the participants.
Within the cycling world, we’ve seen the growth of many types of riding. Bike touring, racing, endurance riding, mountain biking, BMX riding, commuting, track racing, fixie, cyclo-cross racing, and gravel riding.
In my own youth, my family often cycled the miles of crushed gravel bike trials that crisscrossed southern Wisconsin — my brother and I, on matching Schwinn Sting-Rays, and my parents, on French Motobecane touring bikes equipped with center pull brakes and wider tires for better traction on the trails (sounds like a gravel bike, doesn’t it?).
Years later, when my racing aspirations started to drift off-road to the world of cyclo-cross, I had little in the way of bike options to choose from. What I wanted was something with similar racing geometry to my road bike, but I needed great clearance for wider tires and a much wider selection of gears.
A local shop owner convinced me to let him make some modifications to an older Italian steel racing bike I had. After some time under the torch, the frame was ready for cantilever brakes. These mount individually to each seat stay versus one center mount, allowing for greater tire clearance. My 22mm racing tires were replaced with 30mm knobby cross tires made in the Czech Republic, and I now had a cyclo-cross bike for racing off-road.
Today, just as we’ve seen the death of the Century rides (100mi tours) in favor of a much sexier-sounding Gran Fondo (essentially the same thing but a bit more of the Euro flare added), gravel events are multiplying like crazy. This newest branch from the cycling tree is attracting an entirely new universe of riders.
So Just How Does a Gravel Bike Differ From a Road Bike?
A Niner MCR 9 RDO Gravel bike on the left and a Felt AR Aero Road bike on the right.
As the cycling industry has made the shift from rim brakes to disc brakes, essentially all higher-end road bicycles today will accept wider tires (much wider than the 22m tires I grew up riding on). Today, 28 to 30mm tires are more commonplace, with most bikes being able to accept tires up to 35mm or more. So, if I change to wider tires, do I have a gravel bike? Close, but not yet! Whereas road bikes essentially fall into two distinct classes (racing or endurance), a gravel bike has to be versatile to handle a variety of terrain both on or off the road.
With rougher terrain, long hours in the saddle on desolate gravel roads, this means your bike’s geometry must change to provide added comfort to endure these conditions. Where a racing road bike is focused on a low, aerodynamic position (in part to a lower stack height), agile handling especially in and out of corners (thanks in part to a shorter wheelbase and steeper head tube angle), and plenty stiff to handle the watts needed to win a field sprint. These are not the characteristics one would want in a gravel bike.
Where one might see a road bike have a wheelbase (distance between the front and rear wheels) at 97 to 98 centimeters and a more relaxed endurance road bike might push 99 to 100 centimeters, your gravel bike will likely exceed 100 centimeters. This longer wheelbase will absorb road vibration and lead to a more comfortable ride.
As for the head tube, much of the agile handling on a road bike stems from a steeper head tube angle, which can run 71 to 74 degrees. On a gravel bike, this angle tends to be a bit slacker and in the 68 to 71 degrees range, for greater comfort on rough roads. Additionally, a gravel bike will have a taller stack (essentially the distance to the ground from the handlebars), lending to a more upright position.
2. Wheels / Tires
Your typical road bike will use a 700c wheel combined with a tire width of 23 to 32mm with tires that are slick or have minimal tread. This is aimed at reducing rolling resistance on pavement and maximizing speed while keeping the overall weight low.
Gravel bikes need great traction and stability for rougher road surfaces and tend to be equipped with wheel/tire combinations that are 700c x 35 to 50mm. In some cases, the wheels on gravel bikes will even go down to smaller 650b wheels for more stability and strength for the roughest of road surfaces.
Cervelo Apero 5 - one of the more road-worthy gravel bikes, featuring a 1x drivetrain
Probably one of the most significant changes to off-road bikes (like mountain and gravel bikes) has been the adoption of the 1x gearing or a single chainring crankset versus the double chainrings found on most road bikes or triple crankset that mountain and touring bikes used to be set up with. Maybe a decade ago, most mountain and touring bikes used triple cranksets to achieve the ultra-low gearing needed for off-road riding. A triple crankset coupled with seven or eight gears in the back meant a rider had 21 or 24 gears at their disposal, which was both a blessing and a curse. With so many gears to choose from, newer riders did find it confusing where shifting was concerned.
Additionally, so many of the gears were nearly identical in size that one did not really have 21 different gears. If you use the large chainring for the flats and going fast and the inner small ring for off-road and climbs, when the heck did you use the middle ring? Also, with that many gears, the instance of dropping the chain or miss shifting was high, as was jamming the chain between rings.
Enter the 1x drivetrain. One ring up front simplifies everything — no front derailleur to shift and only 10, 11, or 12 gears to consider. Sure, there will be larger gaps between gears (as road bikes typically have one to two tooth differences in cogs on a cassette). But the range is large enough to handle speed on the flats and still be able to tackle steep inclines. A road bike with a 2x front crankset will typically have a rear cassette with cogs running from 11 to 28 teeth or 11 to 34 teeth. A gravel bike will see this change to 10 to 42 or even 52 teeth, which means gravel and mountain bikes will now need a rear derailleur with a much longer cage to be able to effectively handle rear cogs of this size.
Cannondale Topstone Lefty is a more gravel-oriented bike featuring suspension front fork
Just like you find on a mountain bike, some gravel bikes will come equipped with front suspension (like the Cannondale Topstone Lefty) for those truly hitting rough terrain, a dropper seat post, more than two bottle mounts, bosses for fenders/racks, and even flared handlebars — all designed to improve comfort when riding off-road.
So, in making your choice of bike, you need to determine where you will ride the most, especially if you are only going with one bike. All gravel, then the choice is easy. But if you are thinking of doing a little bit of both, there are models that can seamlessly jump between the road and gravel with a quick change in the tire type. Two lightweight options that quickly come to mind are the Cervelo Aspero and Specialized Diverge, but this list could also include endurance bikes like the Scott Addict, BMC Roadmachine, and Trek Domane, all of which can easily handle tire widths wide enough for gravel tires.