To ride on gravelly, sometimes muddy, sometimes stony, roads and paths, it’s good to have a bike with big tires. Of course, mountain bikes have big tires, but one can’t ride fast on them, and the prospect of doing 100km on a full-suspension bike with flat handlebars is not appealing (at least to me). Mountain bikes are great for technical paths and/or for seriously difficult off-road riding, but are ill adapted for long rides that will cover a variety of surfaces from tarmac, through hard-packed gravel, stony lanes to the odd single-track path (on which mountain bikes admittedly come into their own).
The gravel bike – a type of bike that has become fashionable over the last 7 years or so – is basically a road bike adapted to uneven surfaces. Not quite a road bike, mind you, because its geometry (distance between the two wheels, angle of the steering tube, height of the pedals’ axis, …) is subtley different. For non-geeky cyclists, this does not mean much, but these different angles and dimensions make gravel bikes more stable and more comfortable over longer distances than their ‘agressive’ road bike counterparts.
The key, though, is the tires. Road bikes typically take tires that are up to 28mm, maybe 32 mm (this roughly measures how far the tires ‘protrude’ from the wheel – so the more mm the bigger the tires. This should not be confused with the other crucial dimension of tires, which is their diameter, typically 700mm – most common, 650mm, 26 or 27 inches).
Many road bikes have difficulty squeezing in tires of over 25mm – fairly skinny tires that need to be run at high pressure and that can’t absorb the bumps and stones found on gravel roads. Also, these skinny tires don’t have knobs on them to prevent nasty skids whilst cornering on unstable surfaces: their advantage is that they have low rolling resistance and allow for fast riding on good tarmac surfaces.
Gravel bikes can often take tires of 40mm or more (note that a typical commuting bike will have tires of between 30 and 35mm). These larger tires can be used at lower pressure than skinny ones, absorbing more bumps as well as providing better grip. Gravel bikes also have fixtures for mudguards and other attachments that can make the bike useful for commuting, or even for riding on muddy gravel without looking like a chocolate cake when you get home.
Whilst bikes can have any gearing that you choose – it is easy to change the rear cassette (i.e. the cluster of ‘speeds’ on the back wheel) – gravel bikes typically have gears that make it easier to climb steep hills or to push your way through soft muddy paths.
With this type of bike, it’s possible to ride fairly fast on roads (of course, knobbly tires do slow you down a little, and gravel bikes are usually heavier than equivalent road bikes), and really fast and confidently on poorer surfaces.
Given the poor quality of many roads in the eastern townships – and indeed in Québec – maybe gravel bikes are just road-bikes of the future…