What is a gravel bike? Here’s everything you need to know

Thinking about buying a gravel bike? We've got the basics covered

Cannondale Topstone gravel bike

Gravel bikes have exploded in popularity in recent years. It’s easy to see why, with gravel bikes offering versatility in abundance – we’re big fans of gravel bikes and the opportunities for exploration they present riders.

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A gravel bike has a lot to offer the everyday rider looking to mix up their riding on a machine capable of handling the rough stuff, without handicapping itself much on the tarmac.

So what exactly is a gravel bike? In this guide, we’ll cover the key features of a gravel bike. Otherwise, to read about the latest and greatest gravel machines reviewed by BikeRadar, check out our guide to the best gravel bikes on the market today.

What is a gravel bike?

Cannondale Topstone gravel bike
Thinking about buying a gravel bike? Here’s everything you need to know.

A gravel bike is a drop-bar bike designed to let you ride over many different surfaces. The drop handlebar and road bike-like design mean that you can make good progress on the road, but with wider tyres, lower gearing and stable handling you can also head off the beaten track.

Riding a bike designed for multi-terrain excursions means you can link together gravel routes in new ways, taking in sections of gravel roads, forest tracks, trails, byways and bridlepaths. Or you can load up your gravel bike with camping kit for multi-day bikepacking adventures.

Cannondale Topstone gravel bike
Gravel riding means different things to different people, but ultimately it’s about getting off the tarmac and exploring.

Like any bike category, a gravel bike from one manufacturer can look very different from another – and that’s even more the case here, with some gravel machines pitched more towards road speed and light off-road riding, and others bearing more resemblance to mountain bikes.

Choosing the right gravel bike for you depends on the type of riding you have planned. So let’s take a closer look at the design features that define the typical gravel bike.

Frame material

Cannondale Topstone aluminium gravel bike
Gravel bike frames are most commonly made from aluminium or steel.

Like most other bikes, gravel bikes are made from a variety of frame materials.

The most common options are aluminium and carbon.

Aluminium is affordable, durable and relatively lightweight, making it a good material for a budget gravel bike.

Carbon frames are typically lighter than aluminium ones. Carbon can also be engineered to fine-tune stiffness and comfort, and can offer more opportunities for aerodynamic tube shapes (yes, aero gravel bikes are a thing).

Aluminium and carbon aside, you’ll also find options for steel and titanium gravel bikes.

Geometry

Cannondale Topstone gravel bike
Gravel bikes normally have a longer wheelbase and slacker angles than road bikes.

Although it looks like a conventional road bike, a gravel bike is designed for more stable handling off-road. That normally means a longer wheelbase and slacker angles for the frame and forks.

Cannondale, for example, uses its ‘OutFront’ geometry on its Topstone gravel bikes. It’s derived from Cannondale’s mountain bikes and places the front wheel further ahead of the rider to up stability.

A gravel bike will typically give you a more upright riding position than road bike geometry, with a longer head tube and shorter reach.

That should result in more comfort on long rides and also lets you shift your weight around to tackle obstacles and off-road descents.

Cannondale Topstone gravel bike geometry
A gravel bike may look similar to a road bike but the geometry is normally geared more towards off-road stability.

The frame’s tubes will often be shaped to cushion the ride too, particularly in the rear triangle, where curved and flattened sections in the chainstays and seatstays will help with in-saddle comfort. The seatpost too may be designed for extra vibration absorption.

It’s worth considering the type of terrain that you’re likely to want to use your gravel bike on and choosing a bike designed to handle that.

If you’re predominantly wanting to ride on roads, with the occasional off-road track to mix things up, you’ll probably want a bike that rides more like an endurance road bike.

Indeed, many endurance road bikes, like the Cannondale Synapse, now come with the tyres and clearance to handle light gravel riding.

If, on the other hand, you expect to ride your gravel bike mainly on technical off-road terrain, there are machines that come with really wide tyres on smaller 650b wheels and a geometry much more like a mountain bike.

We talk more about this below, along with suspension, dropper posts and other features lifted straight from our MTB cousins.

Tyres

Cannondale Topstone gravel bike
Big tyres are a defining feature of a gravel bike.

A key feature of gravel bikes is tyre size, typically 40mm or so in width. In fact, perhaps more than any other part of a gravel bike, tyre choice has a big impact on the type of terrain you can ride.

The extra volume of gravel bike tyres lets you run low pressures of 40psi or less, adding comfort and traction on uneven surfaces.

There will likely be a tread pattern too, to aid grip on loose surfaces.

How much tread you need depends on the conditions. Dry trails may only need a light file or diamond tread, while tyres for muddy winter tracks will have more aggressive patterns with side lugs, for extra grip and traction.

Tyres and wheels will usually be designed to run tubeless (without an inner tube). That lets you keep tyre pressure down without the risk of pinch flats – where the inner tube gets trapped between the tyre and the rim in a normal clincher setup.

The sealant in the tyre will cope with thorns, flints and other causes of punctures, forming a seal around small cuts in the rubber before too much air escapes.

A gravel bike’s frame and fork blades will be designed with enough room for large tyres, leaving enough extra space to handle any mud that they inevitably collect, though clearances do vary from one bike to the next.

Wheels

Cannondale Topstone gravel bike
Gravel bikes can have either 700c or 650b wheels.

When it comes to gravel bike wheels, you often have two sizes to choose from: 650b or 700c?

650b wheels have a slightly smaller diameter and can be shod with even wider tyres, for even more traction, while keeping the rolling diameter of the wheel plus tyre similar to a road bike, for comparable gearing and ride feel.

Most gravel bikes come equipped with 700c wheels and tyres as standard, with the option to swap to 650b in future if you want, but an increasing number come with the smaller size out of the box – particularly those bikes more heavily focused on off-road riding.

The Cannondale Topstone Carbon Lefty 3, for example, has 650b wheels shod with 47mm wide tyres.

Disc brakes

Cannondale Topstone gravel bike with disc brakes
Disc brakes are a common feature on gravel bikes.

Disc brakes are now commonplace on the latest road bikes and ubiquitous on gravel bikes. In fact, the arrival of hydraulic disc brakes for drop-bar gear shifters helped pave the way for gravel bikes.

Disc brakes offer consistent, effective stopping, whatever the conditions – crucial for gravel bikes – and leave plenty of room for the wide tyres required for off-road riding.

Gearing

Cannondale Topstone gravel bike
A 1x setup like this uses a single chainring with no front derailleur.

Gearing is key when it comes to gravel bike setup.

If you’re heading off-road, you’ll need lower gears to tackle steep climbs and trickier terrain. With grip reduced on loose surfaces, you can’t get out of the saddle so easily when climbing, so need to spin up the gradient to avoid wheelslip.

As a result, gravel bikes should have a 50/34t compact road chainset with a wide-range cassette, at the very least.

Cannondale Topstone gravel bike with double chainset
Double chainsets are also common on gravel bikes.

However, super-compact chainsets are a common feature. Dropping the chainring sizes to 48/31t or 46/30t, in the case of Shimano’s GRX gravel groupset, and pairing this with an 11-32t or 11-34t cassette puts tough climbs within reach.

If you plan on riding your gravel bike off-road on steep or technical terrain, suitable gearing is vital and we’d recommend a super-compact chainset over a standard compact.

Cannondale Topstone gravel bike
Expect to see a wide-range cassette.

Single ring groupsets are another popular choice for riding gravel.

Doing away with the front derailleur and using just one chainring makes for a simpler system, with less to go wrong. You get as much range (or more) as a double chainset, just in slightly larger jumps between gears on the cassette.

The chainring will typically have alternating wide and narrow teeth which, along with a clutched rear derailleur, helps keep the chain in place and running smoothly when it gets bumpy.

Mounts

Cannondale Topstone gravel bike
Mounts like these allow you to attach a range of bags and accessories to your gravel bike.

Another typical feature of gravel bikes is lots of mounts for accessories and luggage.

Some gravel bikes have mounts for mudguards (fenders) and a rack, making them a great choice for all-weather cycle commuting or as a wide-tyred winter road bike.

A typical set of mounting points will also include bolts for a third water bottle under the down tube, for long rides where it may be difficult to top-up on water. You can also use these to hold a tool keg in a bottle cage, keeping your pockets free.

Some gravel bikes also feature mounts for a feed bag on top of the top tube, behind the stem.

You might find additional mounts on the fork blades, to bolt on extra bottle cages or luggage, and some bikes have a mount for a dynamo light on the fork crown.

Other features

Bars that flare out to the drops are a common feature on gravel bikes. The flared drops provide additional stability, improving handling and control off road because you have extra leverage, particularly if you’re descending fast.

The bars will usually have quite a shallow drop, so that you don’t have to reach down too far.

Also helping when descending off-road, and borrowed from the world of mountain bikes, a dropper seatpost may feature on higher-spec gravel bikes.

Cannondale Topstone gravel bike
Some gravel bikes offer suspension.

Dropper posts are controlled by a lever on the bars to lower or raise your saddle, letting you get it out of the way on steep or rough descents.

Increasingly you’ll find suspension features on gravel bikes too. The Cannondale Topstone Carbon has a suspension system called Kingpin that’s built into the seatstays and gives up to 30mm of movement.

That’s joined on the latest Topstone Carbon Lefty bikes by a single-leg Lefty Oliver suspension fork with 30mm of front-end travel.

Electric gravel bikes

Cannondale Topstone gravel bike
If you want to power-up your ride, consider an electric gravel bike.

Electric bikes are quickly growing in popularity and that includes e-gravel bikes. A growing number of electric gravel bikes are emerging from a range of brands.

E-gravel bikes provide electric assistance while you pedal (up to a certain speed, when the motor will cut out) – handy when tackling steep climbs or if you want to venture further off the beaten track.

Cannondale Topstone gravel bike
Ebike motors are often housed in the bottom bracket area.

The amount of assistance you get will depend on the specific electric bike motor used, while range depends on the battery size, the terrain you’re riding and the level of assistance required (most systems offer a number of assistance levels).

Gravel bike vs road bike

Cannondale SuperSix Evo road bike
A road bike will typically have a more aggressive, go-fast geometry than a gravel bike.
Cannondale

As we’ve mentioned above, a gravel bike will typically have a less aggressive setup than a road bike. That means that you sit more upright and in a more relaxed position, for improved stability and comfort.

Plus you’ll have room for wider tyres with extra tread and a wide gear range that includes lower ratios.

But despite this, you’ll probably find that a gravel bike isn’t a lot slower on the road than a conventional road bike, particularly if you tailor your tyre choice towards riding on tarmac.

Gravel bike vs cyclocross bike

Cannondale Super X cyclocross bike
Traditional cyclocross bikes are focused on racing.
Cannondale

Wide tyres, big clearance, lower gearing – these are all features of cyclocross bikes, so what’s the difference between a CX bike and a gravel bike?

Whereas a gravel bike is designed for endurance riding and exploring, a traditional cyclocross bike is geared to racing, usually over an hour or less.

So a crosser will have a more aggressive, twitchier geometry that helps you accelerate fast and steer around tight obstacles on a race course, rather than the all-day riding position of a gravel bike.

And a cyclocross bike’s tyres will normally be narrower, to comply with race regulations (UCI-sanctioned events only permit tyres up to 33mm wide) and help cut through muddy or sandy ground.

As a result, there might not be as much clearance as a gravel bike and you probably won’t get as many mounting points for mudguards and other accessories either.

Gravel bike vs mountain bike

Cannondale Scalpel mountain bike
Mountain bikes offer geometry, tyres and suspension better suited to more extreme off-road riding.
Cannondale

Gravel bikes borrow many features from mountain bikes, such as their geometry designed for stability, suspension features, wide tubeless tyres and wide-range gearing.

But the drop bars and more aggressive gearing of gravel bikes make them more enjoyable if your rides include any tarmac or faster, less technical off-road terrain.

However, while gravel bike gearing may be significantly easier than road gearing, it’s not a match for the range offered by a proper mountain bike groupset.

Mountain bike tyres will also be wider and grippier, and mountain bikes will offer more effective suspension than what you’ll find on even the most cushioned gravel bikes.

For a lot of light off-road terrain, a gravel bike is just as effective and will be lighter than an equivalent mountain bike, but once you start venturing onto technical trails, mountain bikes are the winner.

Gravel bike vs hybrid

Cannondale Quick hybrid bike
A hybrid bike offers an alternative to a gravel bike for commuting or riding on light off-road trails.
Cannondale

Like gravel bikes, hybrid bikes will usually have wider tyres and lower gear ranges than a road bike, but with flat bars rather than drop bars.

Hybrids tend to be geared more towards road use and cycle commuting though, so they’ll usually have less aggressive tread patterns on their tyres.

Without lots of mud to deal with, there may be less clearance in the frame, but you’re still likely to find mounting points for mudguards.

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Still, that all leads to less off-road ability, so while hybrid bikes are a good option for commuting, leisure riding and light trails, if you do venture onto anything remotely technical you’ll have to take things more gently.