Even though road bikes look most like gravel bikes, they are probably the least suitable bikes out of this list due to their stiff build and often lack of both disc brakes and wide tire clearance. However, it is possible to tweak your road bike and make it more suitable for gravel adventures.
Upgrade to wider tires
Wider tires result in more grip, more stability in turns, and crucially: less vibrations. It is generally recommended to run the widest tires that your frame and brakes can take. This is absolutely the most important upgrade you can make so it is worth investing in gravel-specific tires.
Although now common on newer road bikes, many older models will not support disc brakes. If your bike is compatible with them, we would highly recommend installing disc brakes as this will result in far superior braking and will allow you to run wider tires which has many advantages.
There are a couple things which could be optimised in the drivetrain. Getting a derailleur with a clutch as seen on mountain bikes, will dramatically reduce the amount that the chain moves and falls off with the increased impacts of gravel roads. If you are investing in a new derailleur to achieve this, getting a longer cage derailleur would be preferable. This will allow you to install a cassette with larger cogs to ensure a lighter gear for climbing. If getting a longer cage derailleur is not an option, you would be limited in how large a cassette you could run. Alternatively, you could buy a “road link” from wolf tooth components which allows you to run a wider range cassette.
If you are willing to invest in a whole new drivetrain, getting a “one-by” mountain bike drive train is also a great option, however this would cost more.
A small upgrade which can make a big difference is getting a more comfortable saddle. Road bike saddles are generally very hard and aggressive, and this can make them uncomfortable when riding on bumpy roads. Getting a more cushioned saddle will improve your comfort on long rides.
Getting thicker bar tape will not only improve comfort, but it can also reduce fatigue. Road bikes, obviously, do not have suspension, so when descending on gravel your hands and arms take a beating. Thicker bar tape will help reduce this and allow you to ride for longer.
Mountain bike pedals and shoes
Mountain biking shoes are generally far more durable than road biking shoes, and this makes them a better long-term investment regardless of what bike you are using. They are also far more appropriate for walking if this is ever required. However, this does require you to use different pedals which is a downside if you are looking to save money.
Getting a cheaper set of wheels
This is not a necessary upgrade and is only worth it if you are going to switch between riding road and gravel often. Getting a cheaper set of wheels will prevent your expensive road-rims from getting damaged. You could also keep your wider tires and larger cassette on this set of wheels which makes switching between road and gravel bike extra easy.
It should be noted that these modifications and upgrades are not a necessity, however, they will make your gravel rides far more comfortable and enjoyable.