There are a lot of people who are new to gravel bikes; some of them are experience cyclists, other are newer to the sport. Either way, there are a lot of new things to consider when looking at road bikes, whether you come from a mountain bike background or a road one. In this guide, I’ll aim to outline the key decisions you need to make, and give you the the information to make them.

Road VS Off Road Balance

It goes without saying that every bike has a different bias. When designers sit down to sketch their initial outline of a bike, they will have a certain rider or group of riders in mind. Depending on who they’re rethinking of, they will design the bike with a bend towards one side of the spectrum or the other. They can either choose to put the bike towards the road bike side of the spectrum, or towards the off road side.

A bike designed on the road end of the spectrum will feature steeper, more responsive geometry, narrower tyres with less pronounced tread and potentially higher gearing and narrower bars, maybe even without flare. On the other hand, a bike with a more off road bend will have more relaxed geometry for more stable handling off road, wider tyres with a deeper tread, and lower gearing to help with the steeper climbs found off road. They may even feature some sort of suspension to smooth out rough terrain and help keep the rider in control.

The Specialized Sequoia #steelisreal

As for choosing a side of this particular coin, it all comes down to where you see yourself riding, and the terrain you will encounter. If you’re seeking a bike for your road commute that features some canal tow path, or cuts through the local pond, then a bike with a more road bend will be most appropriate. If, however, you want to explore every last vestige of rideable terrain in your area, and aren’t afraid of heading well off the beaten track, then I’d go for something with a more off road flavour to it.

Geometry

The geometry of a gravel bike is inherently different to any other sort of bike out there. Having said that, gravel bikes do take cues for every other segment out there, so there will be some elements that you’re familiar with.

A key indicator of a bikes intentions can be the head angle. Generally speaking, a slacker head angle will provide more stable handling off road, at the expense of responsiveness on the road. This is especially apparent if you’re trying to thread the needle through a high speed peloton, or carve your way through a tight crit course. Like almost everything with bikes, its a compromise, and you have to decide what you’re willing to give up on.

Another key feature of geometry is stack and reach. This is a key measurement for sizing, as it tells you how high the handlebars are, and how far away they are, relative to the BB. Generally speaking, compared to a dedicated road bike, a more off road orientated gravel bike will have a higher stack and shorter reach. The effect of this is two fold; firstly, the higher stack makes it easier to spend time in the drops, where you have much more control over the bike and can apply the brakes more easily. Secondly, the shorter reach compensates for the often longer reach of hydraulic shifter hoods, keeping your overall stretch in check. That being said, you don’t want to be quite as long and low on your gravel bike as you might on a road bike, especially if you already run a fairly aggressive position.

There are two other, interconnected factors worth considering; chain stay length and wheelbase. Obviously, longer chain stays lead to a longer wheelbase, and the effect that they have on a bike is similar. Generally speaking, a longer bike will lead to more stable handling, especially off road, but this does come at the expense of agility. I find that this especially apparent on loose over hard surfaces, where the bike can be liable to “float” around on the loose top of the surface. So again, if you’re going to heading into more off road terrain, longer would be better, but it’s a compromise.

A lot of these compromises become especially apparent if you ride in a tighter group, where constant micro adjustments are needed to ensure you don’t take out the rider next to you, so bare that in mind if you plan on using your bike for the club run.

Tyre Size

Surprise surprise, there’s another compromise to be made here! I won’t discuss tread pattern and rubber compound in this section, but it does have a roll to play as well. There are two size variable to consider; width and diameter. There are a few gravel bikes that come stock with 650b or “road plus” wheels, and even more frames which are compatible with the standard. This set up uses a smaller diameter tyre with a much higher volume casing, and larger width, to create a tyre with the same outer diameter as your standard 700c one, but with much higher air volume for better cushioning and control. However, as you can imagine, this puts more rubber in contact with the ground, and so therefore rolls slower on nice smooth tarmac.

The other factor to consider is tyre width. All other things being equal, a wider tyre will provide a bigger contact patch, which will produce more grips. Also, the larger air volume will help cushion the ride on poor surfaces. The downside to this, is that the tyre will also roll slightly slower on nice tarmac. There are ways to minimise this using fancy rubber and interesting tread patterns, but that’s not for this section.

Regardless of size, tanwalls are always better

Ultimately, I’d suggest just running the stock rubber on the bike that you choose until its worn, or until you notice its lacking in some are, and then you can dive down the rabbit hole that is tyre choice with a bit more knowledge on what it is that you need from your tyres.

Frame Material

More so than any other discipline, almost any frame material can be valid choice when it comes to gravel riding. As a trend that was born from smaller, independent frame builders working out of garages and small warehouses on an industrial estate near you, metals such as steel and titanium where the original choice for gravel bikes. Of course, this is in no small part due to these materials ability to be relatively easily worked with on a small scale, but they do hold some other advantages.

Metals tend to stand up better to impacts than carbon, especially in the long term. This is especially important when venturing off the beaten track, as there are a lot more pointy rocks just waiting to be thrown up by your front tyre, straight into your downtube. Multiply this by hundreds of rides over thousands of kilometres, and multiple years, and you can see where problems can start to develop.

That being said, multiple companies have been making mountain bikes out of carbon for years with very few problems, and the abuse that a mountain bike takes makes a gravel bike look like a museum piece. Therefore, I wouldn’t rush to exclude carbon on the basis of strength.

To give a brief overview of each materials properties, I’ve created a little table for reference. Please bare in mind that these are gross generalisations, and there are exceptions to all of these rules. However, this should give you a good primer on different materials, and act as a jumping off point.

Material Properties Steel Has a slight flex that gives a very smooth ride quality, easier for small builders to work with. Heaviest option, not too expensive, provides a relaxed rather than sporty ride quality Aluminium Stiff and light, a very common choice for entry level to mid range bikes from large manufactures. Although not easy to work with, the bike industry has optimised the processes. Can be a bit harsh over rough terrain. Carbon A bike designers wet dream. The lay up and orientation of the individual fibres can be adjusted to tune the properties for different places, to give different properties as needed. This means it can be light, strong, stiff, flexible and comfortable as needed. Does come with a higher cost, and can be more prone to catastrophic failure Titanium The most premium metal, with a price tag to match. However, its lighter, stronger and stiffer than aluminium, whilst having a springy ride quality similar to steel (some would argue better) for increased comfort.

Gearing

Gravel bikes often come with lower gearing than comparable road bikes for a few reasons. Firstly, its to account for the greater roll out, or outer diameter, of the larger tyres that are often seen on gravel bikes. To compensate for this, lower gears are used, normally on the front chainrings. To give you an idea of the effect, this table shows the speed you’d be travelling whilst peddling at 80rpm with various size tyres in a 50-11 gear, a common top gear on many bikes.

As you can see, the effect is relatively negligible, but its accounted for none the less. This is the sort of detail that bike designers go into.

The other reason that gearing is changed is to account for the steeper climbs found off road. This requires lower gearing to maintain a useful cadence, or peddling speed. If you gear the bike too high, then you’ll have to really push on the pedals to get yourself up a climb. This is bad for your knees, as well as being bad for your endurance over the course of the ride.

Another factor in gearing is the prevalence of bikes with only a single chainring in the gravel segment. Also know as 1x, or one by, these bikes use much larger range rear cassettes to give you the range to get up and down hills. They often sacrifice a bit of overall range, usually at the high speed end of the gears, but bring a host of advantages. Firstly, bike designers have a lot more flexibility to design the frame when they only need to fit in one chainring, allowing for some interesting shapes that wouldn’t otherwise be possible. Secondly, it massively simplifies gear selection for the rider. When you’re breathing through your eyeballs on that especially tough climb that always gives you a hard time, and are desperate for an easier gear, you don’t have to worry about cross chaining or what chainring your in. You just have one shifter, you hit it, and you get and easier gear. Much simpler, and makes for an easier life. Lastly, because the front chainring doesn’t need to ever let go of the chain to shift, it can be designed with a profile to really grip onto the chain and ensure it never lets go. Many companies use some variation on a narrow-wide profile, although other solutions including hooked teeth, exist. This, combined with a clutch mech, should mean that dropped chains are a thing of the past; especially useful on rough terrain.

Tyres

In addition to width and diameter, there is also a large variety of options in terms of tread pattern and rubber compound. This could be a whole article in itself, so I’ll just cover the basics here and leave some more in depth analysis for another day.

The 3T Exploro can be fitted with 650b “Road Plus” wheels

Tyres with a more pronounced tread pattern will offer more grip on loose and rough surfaces, due to the tyre being able to dig into the surface more effectively. The compromise (you knew there’d be one) is that they tend to have higher rolling resistance on the road, causing the bike to feel sluggish on smoother surfaces. There are a number of tyres that reduce the impact of this by having slick centre treads, with more pronounced tread on the shoulders of the tyre. This gives a tyre that rolls respectably on the road, but has the ability to bite into the terrain when its leant over cornering on loose surfaces. This style of tyre is worth considering if you split your time evenly between the tarmac and the dirt.

When it comes to rubber compound, things start to be come really confusing. Many brands will use multiple compounds of rubber to get different properties from different locations on the tyre. As a rule, a softer rubber compound will provide more grip, but this comes at the expense of ware life. A harder rubber can roll slightly better, and will last much longer, but offers distinctly less grip. If a soft rubber compound is used on an shoulder tread with discrete knobs, then under high cornering load on hard, grippy surfaces like tarmac, these knobs can deform and squirm, creating a vague feeling. This effect is increased if the knob is made from a particularly soft rubber, as they can’t hold their shape as well. Confusingly, this same effect increases grip off road, so be aware.

Suspension

A few gravel bikes are starting to come with varying forms of suspension. Some are reasonably conventional, life Fox’s 32 Step-Cast AX fork, which is essentially a shrunken version of their 32 Step-Cast mountain bike fork. Others, such as the Lauf Grit are a bit more out there, and designed from the ground up for gravel use. Some, such as the Specialized Future Shock, are kind of suspension but not really, and sit off to one side of the rest of the debate.

As a general rule, you should only consider suspension if the majority of your riding is going to be off road. Even a light fork will add quite a bit of weight over a nice, light carbon fork, and the performance gains occur in a narrow range of terrain and applications.

If you’re thinking of a suspension fork, then I’d suggest you need to think about whether you want a gravel bike, or a mountain bike. Not to say that these forks don’t have their place on a gravel bike, as they definitely do, but its a narrow group of people that stand to benefit from them.

Conclusion

As with any major purchase, there’s a lot to consider here. And, as always when it comes to bikes, its all about where you’re willing to compromise. If you plan on spending the majority of your time on the road, then you should probably give up on some terrain taming features. Conversely, if you’re going to be spending a lot of time on the dirt, then you’ll want a bit more comfort and stability than your road going brethren. Have a proper think about what bought you to considering a gravel bike in the first place, and if you’re lucky enough to already have a bike or two in the collection, then take them into account. Then, go out, buy a bike, and enjoy your riding. The hard parts done!