Gravel vs Mountain Bikes – What’s the Difference?

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The classifications for bikes these days have become very specialized. You have mountain bikes, trail bikes, road bikes, touring bikes and now gravel bikes. 

You want to go off-road on your bicycle, but which is the best option for you? 

Mountain or gravel bikes?

Perplexed? Don’t worry, we’re here to help you figure this out by giving you a detailed comparison between mountain bikes and gravel bikes.

  • Gravel bikes are sometimes referred to as adventure bikes. They retain the drop bars inherent to road bikes but with distinct differences in geometry and tire sizes. The idea is to retain speed while making these bikes durable enough and with enough traction to take on off-road terrain. Tires are designed for bike rides that cover a variety of different surfaces, from paved to dirt and gravel.
  • Mountain bikes have little interest in paved roads or even gravel for that matter. These are bikes that are meant to be ridden on dirt trails over roots, fallen log, through streams and across other obstacles. These are true off-road bicycles.

Let’s take a deeper look into the differences are between gravel bikes and mountain bikes.

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Type of Terrains Ridden

When comparing the differences, it’s best to talk about the type of terrain, which is truly what divides the two. 

Gravel bikes are best for terrain that ranges from smooth tarmac to dirt roads and hard-packed gravel. 

Why not ride a mountain bike in these conditions? 

The answer is simple, speed. The drop bars of a gravel bike allows you to cover the aforementioned off-road terrain much more quickly than on a mountain bike due to the geometry of the frame and drop bars that put the rider in a much more aerodynamic position. 

Such terrain also does not require larger tires or suspension systems, which add weight and drag, ultimately slowing you down.

Mountain bikes, in comparison, are designed to take on much rougher terrain. 

This includes the rough and tumbles world of singletrack, in which you face a multitude of roots, logs, rocks, drops, and varying degrees of uneven terrain.

For that, you need a suspension, heftier tires, flat handlebars, and bike geometry that allows you to maneuver through this tough terrain.

Frame Materials

Titanium is perhaps more prized than even carbon when it comes to gravel bikes.

Why? 

Titanium is as strong as steel but significantly lighter with better shock dampening qualities. Because of their superior strength, titanium frames do a better job of handling racks, panniers, and bikepacking gear than carbon frames. 

That said, because titanium is very difficult to work with, it’s nearly as expensive as carbon. For that reason, few complete gravel bikes come with titanium frames. 

Titanium frames are usually sold separately, requiring a custom build. Litespeed, a company that specializes in titanium frames, does offer a full line of titanium frame gravel bikes. 

Though not as strong or durable as titanium, carbon frames are still the frame material of choice for high-performance gravel bikes because carbon is the lightest and stiffest of all frame materials. 

A high-end carbon gravel bike can weigh less than 9 kg. That said, be aware that carbon is more susceptible to damage from impact. And, only high-quality carbon frames will approach the damping qualities offered by titanium or even steel gravel frames.

With mountain bikes, expect to find mainly aluminum frames.

Aluminum is stiff, relatively light, and durable, all qualities that fit the needs of a mountain bike. 

As with gravel bikes, carbon frames make up the high end of the mountain bike market. For the same reasons, carbon is prized with gravel bikes. Carbon has the magic combination of being both stiff and lightweight with good shock-absorbing qualities when skillfully designed. 

A carbon frame mountain bike is at a greater risk of being damaged. And, given the nature of mountain biking, that is an important risk to consider before investing in a carbon frame mountain bike.

A huge difference you’ll also notice with the frame of a gravel bike or mountain bikes is the front fork

Front forks on mountain bikes are designed to absorb shocks, so they are built with a front suspension.

Gravel bike forks, on the other hand, have rigid forks. They are built using one of three different materials; aluminum, carbon, titanium, or steel with titanium forks offering the highest level of comfort.

Frame Geometry

The geometry of a gravel bike is very close to that of a road bike with a few exceptions. The bottom bracket on a gravel bike will generally be lower. This lowers the rider’s center of gravity, helping to add stability, an important quality when traveling over uneven ground.

Gravel bike frame geometry will also put the rider in a more relaxed, less aggressive position than a road bike. 

This means a slacker head tube angle for more forgiving steering and a higher head tube for a more upright position on the bike. Also, expect to find longer chainstays on gravel bikes. This increases the wheelbase, also adding to the bike’s overall stability. 

In a nod to mountain bike frame geometry, expect to find top tubes that slope downward, allowing more standover height. This makes mounting and dismounting easier, which is a necessity for off-road cycling.

Some pessimists classify gravel bikes as merely old-school mountain bikes in disguise. Such is not the case. There is a clear distinction between mountain bike geometry and gravel bike geometry. 

Mountain bikes tend to have a high bottom bracket, which facilitates riding over obstacles. 

Other differences include shorter chainstays, which make mountain bikes more nimble for technical singletracks as well as making it easier to hop over those obstacles. Mountain bikes also have more steeply dropped top tubes, allowing for easy entrance and exit, a necessity for trail riding.

Wheel and Tire Sizes

Gravel bikes most closely resemble their road bike cousins. The most noticeable difference you’ll see between the two is tire sizes. 

Tires are much beefier on gravel bikes compared to road bikes. 

Expect to find 700c wheel sizes on gravel bikes with tire widths up to 40 mm or smaller 650b wheels with tires up to 50 mm. These bigger tires are needed in order to handle the off-road terrain that gravel bikes are designed to handle.

At one time, mountain bike wheels were smaller than road bike wheels. 26-inch wheels were the standard for most mountain bikes, smaller than the wheel size of road bikes. But that all changed with the adoption of 29-inch wheels and later 27.5-inch wheels for mountain bikes. 

Why the change? 

Larger wheels more easily roll over obstacles. Why then the trend back to smaller 27.5-inch wheels. Smaller wheels are easier to maneuver through tight turns.

In addition to different wheel sizes, tires also vary significantly between mountain bikes and road bikes. 

Mountain bike tires are designed to handle off-road surfaces.

This is why you’ll notice significant drag when riding a mountain bike on the tarmac. Mountain bike tires have deep treads that are designed to bite into the dirt, mudrocks, and all other manners of the off-road surface. While mountain biking tires help for off-road surfaces, they make for poor roll on paved surfaces.

Gravel tires, in comparison, are designed to handle a variety of different types of surfaces ranging from tarmac to packed dirt, to gravel.

As such, gravel bike tires are designed to handle moderate off-road surfaces but still be smooth enough to have a good roll on paved or packed surfaces.

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Cockpit

Another noticeable difference between mountain bikes and gravel bikes is the handlebars. 

Gravel bikes mimic road bikes, with drop handlebars and longer stems. 

Drop handlebars allow for multiple different hand positions. This fits with the versatility of the bike. While on smoother terrain it may make sense to be in the drops to maximize aerodynamics, on uneven terrain the hands move to the hoods to improve stability.

The stem length also facilitates this. Gravel bikes typically have longer stems, which makes steering more forgiving and therefore more stable.

That’s not to say that there aren’t differences between road bike handlebars and gravel bike handlebars. Gravel bike handlebars are often flared to allow for better control in the drops while on uneven terrain. You’re also just generally more likely to see wider set handlebars on gravel bikes than road bikes.

The cockpit on mountain bikes feature flat bars. 

Flat bars facilitate a more upright position, which is much more conducive to handling changes in terrain and twists and turns. Flat bars also allow for better grip on the handlebars, a necessity when taking on very uneven terrain. 

In addition, stems are usually shorter on mountain bikes. Whereas a stem on a road or gravel bike might be 90 to 120 mm, the stem on a mountain bike is typically 80 to 90 mm. The short stem makes steering more responsive, a necessity for winding single track that requires quick turns. 

Brake levers and gear shifters are also more easily accessible on flat bars, which is important given all the quick gear changes and braking that takes place while navigating technical single track.

Drivetrain and Gearing

If there’s one trend that both mountain bikes and gravel bikes are moving in, it has to be drivetrain. Both bike styles are in the midst of a love affair with 1x drivetrains. 

Eexpect to find many single front chainrings paired with 11 or 12 speed rear cog sets. 

1x drivetrains offer simplicity and ease of use that’s appreciated when riding on off-road terrain. They are also more durable and less prone to breaking down. With smaller front chainrings, usually 32t in mountain bikes and 40t in gravel bikes, they also offer better clearance than double chainring drivetrains.

Rear cogs on gravel bikes usually go up to 42t. Mountain bikes often opt for larger cog sets. SRAM and Shimano have developed a range of cassettes that go up to 50t and 51t respectively, which makes steep climbs much more doable. That said, a broader range translates into bigger jumps between gears, which means shifting is not as smooth as drivetrains with more compact cog sets.

Although it may at first seem like there are a lot of similarities between mountain bikes and gravel bikes, their uses are really quite different. 

If you need a bike that is primarily for off-road trail riding, then you need the suspension, wheelsets, relaxed frame geometry, and durability that mountain bikes offer.

If you plan on riding on a variety of different surfaces ranging from tarmac to packed dirt or gravel, then you want the aerodynamic frame geometry and versatile wheelsets and tires that gravel bikes have to offer.

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Summing Things Up

Although it may at first seem like there are a lot of similarities between mountain bikes and gravel bikes, their uses are really quite different. 

  • If you need a bike that is primarily for off-road trail riding, then you need the suspension, wheelsets, relaxed frame geometry, and durability that mountain bikes offer.
  • If you plan on riding on a variety of different surfaces ranging from tarmac to packed dirt or gravel, then you want the aerodynamic frame geometry and versatile wheelsets and tires that gravel bikes have to offer.

John Philips

John is a man with many hobbies. He’s been mountain biking for five years, he swims every day and he has an interest in cooking.