Gravel or mountain bike - what's the best bike for an adventure?

Adventure beckons, but on which bike do you answer the call? It’s a tricky question: do you take a gravel bike or a mountain bike? Yes, they can both ride off road, and yes, they can both ride on tarmac, but which bike is best, and which is the right bike for your next adventure?

To get a proper understanding of which bike is right for you, and to find out which one is faster over various terrain, we pitted a mountain bike and a gravel bike head-to-head. Our test will help you get to the bottom of the question of which is fastest, which is more capable, and which is best for adventures.

The bikes

Gravel bike

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Canyon Grail CF SL

First up, the gravel bike, the beefed up cousin of the road bike. With drop handlebars and relatively narrow tyres, these bikes ride similarly to a road bike, but they have increased tyre clearance and stable geometry to give them off-road capability too.

Gravel bikes are most at home on rough tracks and gravel roads, but they roll well enough on tarmac to be fun and efficient on the road. Equally, they’re durable enough to put up with the bigger knocks and impacts of proper mountain biking, although they won’t be as easy to ride on the really rough stuff as a mountain bike. All in all, they make a great bike for covering distance over a range of terrains, even if you might have to walk on the properly technical stuff.

For our test, we used a Canyon Grail CF SL, Canyon's top end carbon gravel machine, equipped with 2x Shimano GRX.

Mountain bike

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Canyon Exceed CF SL

A mountain bike, specifically a cross-country mountain bike, might be slower on the tarmac and smoother surfaces, but they can make extremely capable and dependable bikes for long, adventurous rides. With a mountain bike, you can keep riding where a gravel bike would have you off and walking, and you can ride confidently over rougher terrain without worrying about the health of your bike.

For adventures that truly head off the beaten path, a mountain bike can be more dependable and capable. They give better control, better grip and better suspension, albeit at the expense of weight, aerodynamics and rolling resistance.

Representing mountain bikes, we used Canyon's Exceed CF SL, a lightweight carbon hardtail with 100mm of front suspension, set up with Shimano's XTR groupset.

Speed test

To know which bike is best for an adventure, we want to know which one is faster on various terrains. Thankfully, a few years back, we sent Si and Chris out to find out. They arranged a set of tests between a gravel bike with 42mm tyres and a hardtail cross-country bike with 55mm tyres. Here’s how they got on. It’s only a rough test between two bikes, but it gives us a good idea of which bike is best on each type of terrain.

Test 1: Tarmac

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Thinner tyres; better aerodynamics. On road, the gravel bike is fastest

Si and Chris started by putting the bikes head-to-head on the tarmac with a 4km climb followed by a 4km descent back down again. Why tarmac, we hear you ask? We find that on most adventures, no matter how wild, there are usually a few kilometres of tarmac on the route, so performance on paved roads is really important for an all-round adventure bike.

On the tarmac course, which took Si and Chris about eight and a half minutes, Chris was 11 seconds faster on the gravel bike, and Si was 27 seconds faster on the gravel bike. Taking an average of that difference, and doing some quick maths, we can see that in an hour’s cycling on tarmac, the gravel bike could gain about 2:49 on the MTB.

Test 2: Easy / smooth gravel

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Smooth gravel

How would our two bikes compare on hard packed gravel? We tested the two bikes over a ‘real world’ course, with corners, some small changes in elevation and a mix of different surfaces, from hard packed rock to small gravel. So what were the results?

On this terrain, the difference between the two bikes shrank, but the gravel bike was still faster. Over a course which took Si and Chris about six and a half minutes, Chris was nine seconds quicker on the gravel bike, and Si was five seconds quicker on the gravel bike. Over the course of an hour, that translates to a 1:12 advantage to the gravel bike.

Test 3: Chunky gravel

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Chunky gravel

Next, Si and Chris tested the bikes on a rough gravel track. This track is still hard packed, but the rocks are larger and a little looser. How did the bikes get on?

On the rougher terrain, the mountain bike finally overtook the gravel bike. On this course, which took Si and Chris four to five minutes on both bikes, Chris was 13 seconds quicker on the mountain bike, and Si was 11 seconds quicker on the mountain bike. In an hour’s riding, that time difference would put the mountain bike 2:24 ahead of the gravel bike.

Test 4: MTB trails

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Single track MTB trails

Finally, Si and Chris put the gravel and mountain bike head to head on a mountain bike single track circuit. This route had steep gradients, tight turns and rocky sections. This really was the home of the mountain bike.

This course had the biggest time discrepancy between the two bikes of all, with Simon completing it in 5:44 on the mountain bike and 7:01 on the gravel bike. Chris’s results were even more extreme, but that’s because he got a puncture on the gravel bike and had to walk the remainder of the course.

Looking just at Si’s results then, we can see that the mountain bike was significantly quicker, and over the course of an hour, that difference would translate to a time advantage of 13:12 for the mountain bike.

Interpreting these results

To make sense of these results, we need to think about three things. Firstly, aerodynamics. Secondly, rolling resistance, and thirdly, control. On each of the different terrains, the importance of these three factors changes, and with that, the results change.

Aerodynamics

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No matter how low you get, a mountain bike won't be as aerodynamic

On tarmac and smooth gravel, the speeds that Si and Chris were travelling at made aerodynamics really important. On the road, a fit rider can expect to ride at about 30kph, and on fast-rolling gravel, a fast rider can expect to ride in the 20s. At these speeds, the amount of frontal area hitting the wind will really impact the speed at which you can ride.

On a mountain bike, this frontal area is large. The handlebars are much higher and wider on mountain bikes. This is to increase control, and to make room for the front suspension, but it means the rider is in a far less aerodynamic position. Then there’s the bike itself, which has wide, square forks and fat tyres. Nothing about the frame design is intended to be aerodynamic.

On a gravel bike, the rider is put in a far more aerodynamic position. The bars are low and narrow, bringing the rider’s position lower. Plus, the design of the frame is much closer to the more aero road bike.

As the terrain gets rougher, the speeds we ride at become slower. At lower speeds, the aerodynamic differences between the two bikes matter less and less, as the air is hitting the rider slower. As a result, the advantage of the gravel bike decreases as the terrain gets rougher.

Rolling resistance

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Wider tyres are slower on road, but faster on rough ground

This is a complicated one. On the smoother surfaces, the gravel bike’s narrower tyres give it a lower rolling resistance. Its smaller contact patch with the road lets it roll easier, as less energy is being wasted in tyre deformation than on the mountain bike.

Then there’s the issue of tread. Usually, mountain bikes have chunkier tread that increases rolling resistance, but increases grip and control. On smooth surfaces, this extra tread increases rolling resistance even more.

As the surface gets rougher, the fatter tyres on the mountain bike absorb the bumps, as does the suspension. The thinner gravel bike tyre is unable to absorb the bumps of the road, and the bike itself bumps up and down over rough terrain. This kills momentum, and slows the gravel bike down, while the mountain bike ‘glides’ over rough surfaces.

Control

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Drop handlebars don't give as much control as flat bars

Our tests between the mountain bike and gravel bike were intended to be ‘real world’ tests, so we didn’t just send Si and Chris along a straight bit of track. The courses involved corners, climbs and descents, so as things got rougher, the difference in control between the gravel bike and the road bike became a factor.

Of course, on the tarmac, and on the smooth gravel, both bikes offer loads of control and loads of grip, so the difference in speed is entirely down to the differences in rolling resistance and air resistance.

As we moved into the rougher gravel, and especially when on the mountain bike single track, the differences in control became more apparent. To keep rubber-side-down on the gravel bike, Si and Chris had to bring down the speed around corners and obstacles, whereas on the mountain bike they could confidently plough through anything the course threw their way.

So, if your adventure is over particularly rough ground, that increased control you’d get on a mountain bike will translate to higher speeds and greater distances covered.

Things the stopwatch can’t measure

Ride feel

While the two bikes might measure up similarly with a stopwatch, the difference in ride feel is vast. The gravel bike feels agile and nippy: they’re stiff and lightweight, and feel quick to accelerate and turn. Off road, they make easy mountain bike trails feel more difficult, which sounds like a bad thing, but is actually a lot of fun.

The mountain bike, meanwhile, gives the rider a certain feeling of invincibility: you can plough over obstacles and ‘monster truck’ your way along the trails. A mountain bike has a laid back feel that encourages a leisurely pace and a fun-first approach. The downside of a mountain bike - besides the extra resistance on tarmac - is that, when pedalling for a long time on fast-rolling terrain, the large gaps between gears can be frustrating. It can feel like you’re never quite in the right gear.

Durability

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Gravel tyres can't take the hits quite like a mountain bike tyre

Gravel bikes can take a lot more wear and tear than road bikes, but they can’t stand up to the kind of battering that mountain bikes can. In part, this is because of the lighter construction of gravel bikes: they’ll have thinner tubes, lighter components and lighter built wheels. Really though, it comes down to a gravel bike’s lack of suspension or fat tyres. These two features dramatically reduce the stress that goes through a mountain bike frame. Without them, a gravel bike takes the full brunt of any impact directly, without anything to soften it.

Ultimately, you’re probably not going to break your gravel bike by taking it off road – it’s what they’re made to do, after all. But if you are really rough on your bikes, and want to hit bigger rocks, drops and jumps, a mountain bike will hold up better.

It’s no coincidence that on our test with Si and Chris, the gravel bike got a puncture on the roughest trails. The narrower tyres on a gravel bike are both thinner, to save weight, and narrower, to reduce rolling resistance. Both these factors mean that off road, gravel bikes are more likely to puncture, and the rims and wheels are more likely to get dinged, dented or buckled.

So, which is the best bike for an adventure?

Ultimately, it’s terrain dependent. If you want to truly go anywhere in the real wilderness, the MTB might be best. If you want to cover miles over mixed terrain, the gravel bike is a better choice. Learn as much as you can about the terrain you’ll be riding. If it’s smooth and not particularly technical, the gravel bike will be quicker and more fun. If it’s rough and technical, you’ll go faster and have a better time on a mountain bike.