Also known as an adventure road bike, a gravel bikes is one of the better options for drop-bar commuting.
A gravel bike is essentially a cyclocross bike that's been redesigned as a general purpose machine for unsealed roads and tracks rather than for racing around muddy winter fields. Both bike types feature: a frame and fork with clearance for fatter tyres; a road bike drivetrain; and either disc brakes or (occasionally) cantilever brakes. But whereas a pure cyclocross bike may have no frame fittings other than bottle cage mounts, most gravel bikes have fittings for mudguards and a rear rack. These additions, along with frame geometry that isn't focused on head-down competition, make gravel bikes more practical commuters than cyclocross race bikes. They're like drop-bar hybrids.
Compared to a road bike, a gravel bike opens up your commuting route options. You don't have to stick to tarmac. When you do stay on road, however, the fatter (30-40mm wide) tyres will cope better with potholes and other poor surfaces, softening the ride and shrugging off potential pinch-punctures. Tyre choice will depend on the frame and fork, as well as on what you'll use the bike for. Most gravel bikes have room for tyres 28-32mm wide with full-length mudguards and 40mm or more without. Unless you really will spend most of your time off-road, however, avoid using knobbly cyclocross tyres. They will buzz audibly and sap your energy. Smoother tyres with a file-pattern or sipe-pattern tread will be much more efficient.
Gravel bikes under £1,000 will usually have an aluminium frame. Steel ones do exist. At higher prices, the fork may be carbon fibre; for most gravel bikes with a three-figure price tag, it will be aluminium. Compared to a road bike at the same price, where carbon forks are common above about £600, more of the manufacturer's budget goes on the brakes. Whether an aluminium fork matters is moot. It isn't the jarring experience on 40mm tyres that it can be on 25mm tyres.
Mechanical disc brakes are the default equipment on gravel bikes. Cheaper ones sometimes have mini-V brakes or cantilevers. Nearer £1,000, manufacturers sometimes fit hybrid disc brakes, with hydraulic callipers operated by cables. These work well but are quite bulky. Good cable-only disc brakes to look for are Tektro Spyre and Avid BB7
All gravel bikes use 700C wheels, like road bikes, cyclocross bikes and 29er mountain bikes. The rims are wider than road bike rims, the better to support wider tyres. Some will be advertised as 'tubeless compatible'. These have a tighter fit at the tyre bead, so that it's possible - given tubeless rims strips, valves, sealant, and suitable tyres - to run them without innertubes. This saves weight, improves rolling resistance, and means that small punctures will self-seal. Tubeless compatibility is worth looking for if you plan to make the switch; otherwise don't worry about it.
Integrated brake and gear levers are another staple of gravel bikes. Road bike shifters are designed to work with road derailleurs, so the chainset will usually be a compact double, such as 50-34, or a road triple, such as 50-40-30. The cassette will rarely be larger than 11-32. That's not a bad gear range, but for hilly riding it suits lighter loads better. If you plan to carry big panniers, a lower-geared tourer or trekking bike would be a wiser investment. Small panniers are a better bet for gravel bikes in any case, as the chainstays tend to be shorter than a tourer's; you might hit your heels on big bags.
Here are some examples of gravel bikes from £700 to £1,000.
Dawes Discovery Road 2
The all-aluminium Discovery Road 2 is equipped with Shimano's 8-speed Claris groupset and a triple chainset. Claris isn't as slick as Shimano's next tier groupsets, such as Sora and Tiagra, but it works fine and the rear derailleur will accommodate an 11-32 cassette. So it's a shame a 13-26 has been fitted, restricting what could have been a wide gear range. The Schwalbe CX Comp tyres are a bit buzzy for road use, although fine for mixed surfaces. On the other hand, the sturdy 36-spoke wheels should survive the rigours of daily commuting well, and the chainstays are long enough for bigger bags. A shallow drop bar provides plenty of lower-back-friendly hand positions.
Cyclescheme price: £476.61
Marin Gestalt 1
The extra £150 for the Gestalt 1 nets you Shimano's 9-speed Sora groupset, with a compact double chainset and an 11-32 cassette that provides a lower bottom gear than the triple-equipped Dawes. The Tektro Spyre brakes are nicer too: unlike most mechanical discs, both pistons move when you squeeze the lever. It gives a better braking feel and leaves the pads centred over the rotor as they wear. Both the Marin wheel rims and Schwalbe G-One tyres are tubeless ready, making that an easy upgrade. A flared drop bar offers more steering leverage off-road. The aluminium frame has the fittings you want for commuting, although the short chainstays will restrict rear mudguard and pannier clearance.
Cyclescheme price: £578.75
Giant Revolt 1
This is Giant's top model in the Revolt range. There are two cheaper ones, plus two similar women's versions branded Invite. The Revolt 1 has a lighter-weight carbon fork that doesn't omit mudguard eyelets. Gearing is 10-speed Tiagra and is notable for its slightly more compact double (48-34) and its wider-range (11-34) cassette. The brakes are Tektro Spyres. Additional auxiliary levers on the flat part of the drop bar allow braking wherever your hands happen to be, which is handy in traffic. Giant's own-brand PX-2 wheels are tubeless compatible and you could fit ones as wide as 50mm for off-road use - there's room in the frame and fork.
Cyclescheme price: £680.50