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Tech Talk: Road Bikes vs. Gravel Bikes - What's the Difference?

Gravel bikes have been the hottest new trend in the bicycle industry for the past few years. Their practicality and versatility make them a popular choice for many new bike buyers. But what's the difference between a gravel bike and a "traditional" road bike? How do you choose the right one for you?

First off, we'd like to say that the term "gravel bike" makes many of us in the bike business cringe to begin with. That makes the category sound way too limiting, as if gravel roads are the only place where these bikes can be ridden. There aren't even that many gravel roads here in Northeast Ohio. We prefer the term "adventure road bike" and others have taken to "all-road bike" or "any road bike." However, to keep it simple, we'll keep calling them gravel bikes in this article, since that's probably what you Googled to get here.

Long story short, road bikes are designed to go fast on smooth paved roads. Gravel bikes are designed to help you ride comfortably for long distances on a variety of surface types. Here are a few of the design characteristics that distinguish road bikes from gravel bikes and help each do what they do better:

1. Tire Clearance

Road bike frames are typically designed to work with tires from 20mm to 28mm wide. These tires work well for fast riding on smooth pavement, but not so well on rough roads. The photo below on the left (or top) shows a road bike with a 700Cx22mm tire, with not much extra space between the tire and the seat stays of the bike's frame.

Gravel bikes are built to take tires much wider, typically 38mm to 42mm. Some gravel bikes blur the line with mountain bikes, being able to take tires up to 50mm (2 inches) or more! There are many tire options available to let you choose the tire to match the conditions you want to ride. You can use a skinnier, smooth tire if you plan to ride pavement, but swap to a wider, knobbier tire for rides on rough pavement, gravel, or dirt roads. The photo below on the right (or bottom) shows a gravel bike with a 700Cx38mm tire, with plenty of room to go even wider!

Some gravel bikes even let you choose the wheel diameter to best match your riding conditions. For example, a bike might take 700C wheels with tires up to 38mm wide, but let you switch to 650B wheels with tires up to 47mm wide.

Road bicycle showing tire clearance at the rear brake and seatstays

Gravel bike showing tire clearance at the chainstays

2. Stack Height

The "stack height" is a characteristic of a bike's frame geometry that refers to the distance from the ground to the top of the bike's head tube. This height (among other factors) affects your position while sitting on the bike. All else being equal, you'll be sitting more upright on a bike with a taller stack height, while your body will be in a lower position on a bike with a shorter stack height.

Road bikes traditionally have a lower stack height to give you a more aerodynamic and efficient riding position. This will vary among different road bikes, though. For example, a pure "racing" road bike has a lower stack height compared to "endurance" road bikes oriented more towards the recreational rider.

Gravel bikes usually have a higher stack height. This results in somewhat of a sacrifice when it comes to aerodynamics in favor of more comfort, which is preferred by many gravel riders for the long-distance routes typically used for gravel events.

There is a tool called BikeInsights that lets you graphically compare the frame geometries of different bicycles. The image below shows a road bike and a gravel bike comparing the same manufacturer, model year, and frame size. Note how the top of the head tube on the gravel bike (black outline) is significantly higher than that of the road bike (white outline).

Screen capture from BikeInsights.com comparing a road bike and gravel bike

3. Wheelbase

A bike's "wheelbase" is basically the distance between the two wheels, measured from the center of the front hub to the center of the rear hub. Road bikes typically have a shorter wheelbase, giving you quicker acceleration and climbing and more responsive turning. Gravel bikes usually have a longer wheelbase, which provides a more stable feeling when riding over rough terrain.

The difference in wheelbase between the road bike (white outline) and gravel bike (black outline) is evident in the BikeInsights image above.

4. Fork rake & head tube angle

If you draw a straight line down through the middle of the head tube, the angle where that line intersects a horizontal line is the head tube angle. That line represents the steering axis. If you draw a straight line through from the top of the fork to the bottom, then take the distance between this line and the steering axis where they both intersect the horizontal line, this is the fork rake. Both of these measurements affect the wheelbase, but they also affect how the bike "feels" independent of the wheelbase. Informally, they represent how much the front end of the bike is "stretched out." Road bikes have a larger head tube angle but a shorter fork rake, contributing to that quick, responsive feeling. Gravel bikes have a smaller head tube angle but a longer fork rake, which helps to maintain your stability on rough riding surfaces, especially when going downhill.

Once again, the differences in fork rake and head tube angle between the road bike and gravel bike are apparent in the BikeInsights image above.

5. Gearing

Road bikes, especially the more "racing" oriented ones, traditionally have a double crankset with chainrings of 52 teeth and 39 teeth. More modern road bikes oriented towards more casual riders might have a "compact" double crankset with 50-tooth and 34-tooth chainrings to provide more climbing-friendly lower gears.

Compact 50/34 cranksets are common on some gravel bikes, but some come with even lower-geared 46-tooth/30-tooth setups to make climbing steep grades even easier. Also increasingly common are 1x ("one-by") setups with a single chainring and a wide-range cassette. The benefits of this are reduced weight due to not needing a front derailleur and left-hand shifter, plus better reliability because of having fewer moving parts to get mucked up with dirt and mud and potentially fail in adverse conditions.

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6. Accessory mounts

Road bikes usually have two sets of mounting eyelets for water bottles; one on the downtube and one on the seat tube. Some road bikes have eyelets for mounting a rear cargo rack, but this is the exception rather than the rule. Installing a front cargo rack is almost always out of the question. Mounting fenders to a road bike is a challenge in almost all cases.

Since the tire choices are so much more extensive for gravel bikes, they've become a popular option for bike touring, bikepacking, and bike commuting. As such, many (but not all) gravel bikes are designed to accept most of the popular accessories used for these activities, e.g. cargo racks and fenders. Some have multiple water bottle cage mounts, adding one on the underside of the downtube, and sometimes adding a second one to the top of the downtube. Some have mounting eyelets on the top tube for a bolt-on top-tube bag (a.k.a. a "bento bag"). Some have the ability to mount water bottle cages or cargo cages to the fork blades. All of these options can be mixed and matched to your heart's content to provide the best system for you to carry your gear, whether for your daily commute or weeks-long bike adventure.

A gravel bike outfitted for bicycle touring using common bikepacking accessories

Aren't gravel bikes just cyclocross bikes?

Not really. Cyclocross races are events held on mixed-surface courses, but they only last from 45 minutes to an hour. A true cyclocross bike is made for short, intense events like this, so they are designed to optimize speed and handling at the expense of comfort. They are basically road bikes that fit wider tires. Before the gravel bike concept came about, many people used cyclocross bikes for riding on less-than-ideal road conditions. If that's your thing, then more power to ya! But to get all of the versatility and benefits of modern gravel bikes, a true gravel bike is a better choice. Using BikeInsights to compare bikes (once again, comparing the same manufacturer, model year, and frame size), you can see that the cyclocross bike (white outline) has much more in common with a road bike than it does with a gravel bike (black outline).

Screen capture from BikeInsights.com comparing a cyclocrss bike and gravel bike

What about brakes?

Most gravel bikes have disc brakes, and for a while, this was one major difference between them and road bikes, which used to only use rim brakes. With the popularity of disc brakes taking off in the past few years, you are just as likely to see disc brakes on road bikes and cyclocross bikes as on gravel bikes.

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Does a gravel bike have to have drop handlebars?

When we talk about gravel bikes, we usually imagine the drop-bar "roadie looking" style of bikes. However, some gravel bikes, such as the Salsa Journeyer line (formerly known as the "Journeyman"), are available out of the box in both drop-bar and flat-bar versions. Plus, many fitness/hybrid bikes share some of the same features as gravel bikes (upright riding position, long wheelbase, generous tire clearance), so with the right choice of tires, they can make perfectly capable gravel bikes, if an upright handlebar is your preference.

Salsa Journeyman Drop-bar Gravel Bike

Salsa Journeyman Flat-bar Gravel Bike

Giant Escape 2 Disc Fitness Hybrid Bike

Which one is right for me?

If your plan to do your bicycling strictly on paved roads, or if you plan to enter competitive road races, then choose a road bike. If you want the ability to more easily ride on a variety of surfaces, or you want the ability to carry stuff to work or for multi-day trips, then choose a gravel bike. If you need versatility, but you're afraid that a gravel bike won't perform well enough on the road, keep in mind that with the right choice of tires, a gravel bike can be just as capable (and more comfortable) on smooth pavement as a road bike.

Northeast Ohio has a large and growing network of bike routes and trails, both paved and unpaved. In many areas, the quality of the paved roads is not getting any better. Even when you're planning to stick to pavement, it's nice to have the option to detour onto paved and unpaved trails, as well as not be limited to only the best paved roads. This flexibility makes a gravel bike a very popular option.

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