How to choose gravel tyres: a guide to sizes and terrain

Tyres are the only point of contact between your bike and the ground. In the world of gravel cycling, this component is of vital importance: changing your tyres literally changes the character of your bike. Whether you’re looking for maximum speed on tarmac or total comfort on rough trails, the goal is always the same: to find the perfect balance between performance, grip and safety.

What is a gravel bike and why do tyres matter?

Tyres are the only point of contact between your bike and the ground. In the world of gravel cycling, this component is of vital importance: changing your tyres literally changes the character of your bike. Whether you’re looking for maximum speed on tarmac or total comfort on rough trails, the goal is always the same: to find the perfect balance between performance, grip and safety.

The gravel bike bridges the gap between road bikes and mountain bikes, having evolved directly from the world of cyclo-cross. Its strength lies in its versatility: it is designed to ride smoothly on tarmac, yet is equally at home on gravel, dirt and unpaved tracks.

In this context, tyres are the ‘technological heart’ of the vehicle. They are what determine:

• Grip and Traction: Essential for maintaining control when cornering or driving uphill on uneven surfaces.
• Friction and Slipperiness: To avoid wasting energy on tarmac sections.
• Comfort: The ability to absorb ground vibrations.
• Safety: A reliable tyre drastically reduces the risk of falls and punctures.

Gravel tyre sizes: how to read and understand them

Navigating gravel tyre sizes can seem like a daunting task due to the various standards used in the cycling industry. We often come across measurements in inches, millimetres or French codes, which can cause quite a bit of confusion among less experienced cyclists.

Standards and units of measurement: ETRTO, inches and millimetres

To clarify, the most reliable system is the ETRTO standard (European Tyre and Rim Technical Organisation). A label such as ‘35-622’ tells us everything:

1. 35: indicates the actual width of the tyre in millimetres.
2. 622: indicates the inner diameter of the tyre (essential for compatibility with the rim).

Here’s a quick conversion to help you get your bearings:

• 700c: This is the classic road tyre standard (corresponding to ETRTO diameter 622). It is also often referred to as 28″ (inches).
• 650b: Smaller diameter (ETRTO 584), typical of 27.5 mountain bikes. This allows for the fitting of wider tyres, increasing the air volume.
• 29″: It is essentially the same diameter as 700c, but is used in the MTB world to refer to tyres with a very wide profile.

Tyre width: why it’s essential

Gravel tire width is the factor that most influences ride feel. A wider section allows for lower inflation pressure, which increases the contact patch (traction) and improves the absorption of bumps. The most common size ranges for gravel bike tires vary from 30 mm to 50 mm

Diameter	Recommended Width	Ideal Use
700c	35mm – 42mm	Speed, mixed terrain, tarmac and compacted gravel.
650b	45mm – 53mm	Ultimate comfort, mud, highly technical trails and off-road terrain.

How to choose based on soil type and intended use

There is no such thing as an “absolutely perfect” tire; there is only the one best suited to the terrain and your riding style. Every surface requires a specific combination of tread pattern, width, and tire pressure.

In this section, we analyze the various scenarios you might encounter with your gravel bike to help you choose the optimal setup for every situation.

Mixed terrain and tarmac: low-rolling-resistance tyres

If your typical route mainly consists of asphalt, bike paths, and compact gravel roads, priority must be given to smoothness. In these cases, semi-slick tires are the ideal choice: their design features a smooth central tread that reduces rolling resistance, ensuring speed and responsiveness on hard surfaces.

The side knobs, though subtle, offer good cornering grip, preventing loss of control when tackling light gravel or slightly uneven sections. This solution is perfect for those into performance or competitive gravel riding, where every watt counts and the overall weight of the setup is a crucial factor.

Ideali per:

• Gravel racing
• Quick exits from mixed-asset funds
• Urban commuting with sections of unpaved road

Off-road and B-road: all-round tyres

For those who love venturing onto backroads, rural gravel, and beaten paths, versatility is key. In these cases, it is advisable to fit tires with medium, uniform tread patterns distributed evenly across the entire surface. This type of design ensures an excellent compromise between grip, durability, and comfort, making the tire capable of adapting quickly to changing terrain.

A versatile tread pattern ensures stability on both loose gravel and dry dirt, without excessively sacrificing rolling efficiency on paved sections. It is a highly popular choice among cycle tourists, exploration enthusiasts, and those who tackle medium-distance routes with varying terrain.

Ideal for:

• Bikepacking and cycle touring
• Long-distance mixed runs
• B-roads and dirt tracks

Technical terrain, mud and extreme off-road driving

If your goal is to maximize traction and fearlessly tackle challenging terrain—such as wooded trails, muddy singletracks, or off-road descents—then you need a tire with tall, widely spaced, and aggressive knobs. This type of design is engineered to shed mud quickly, preventing buildup and maintaining an effective grip even on slippery, wet, or uneven surfaces

An aggressive off-road tire inevitably sacrifices some rolling efficiency on asphalt, but offers superior control on steep gradients, roots, and wet rocks. It is the closest setup to an MTB configuration, ideal for those who push their gravel bikes to the limit and seek a technical, extreme experience..

Ideal for:

• Technical trails and mud
• Gravel trails and challenging descents
• Winter outings or outings in changeable weather

Tyre structure and technology

When discussing gravel tires, it is easy to focus solely on the tread pattern or size, but much of the performance is determined from within, by the tire’s internal construction. Elements such as the bead, casing type, mounting system, and puncture protection technologies profoundly influence comfort, durability, reliability, and handling on every ride.

Headband: rigid vs flexible (Kevlar)

The bead is the inner part of the tyre that is secured to the wheel rim. There are two main types: rigid (made of steel) and flexible (made of synthetic materials such as Kevlar).

• Rigid band (steel): This solution is more economical and robust, and is often found on entry-level tyres. However, it is heavier and less practical when it comes to transport and fitting. It does not fold easily, so it is not suitable as a spare tyre to carry in a rucksack. Furthermore, it can be more difficult to fit and remove, especially in an emergency or on narrow rims.
• Flexible band (Kevlar): Also known as ‘foldable’, it is lighter, folds easily and can be carried without taking up too much space: perfect for bikepacking and long cross-country rides. Tyres with flexible beads are often associated with higher-quality casings, featuring higher-performance materials and advanced technologies. Fitting them is generally quicker and easier, even in the field.

Inner tube or tubeless?

Today, tubeless tires are the standard in gravel riding. By eliminating the inner tube, you can ride at lower pressures without the risk of “pinch flats,” drastically improving both comfort and grip. Additionally, the sealant inside automatically repairs small punctures.

TPI, compound and puncture-resistant reinforcements

The tyre carcass is the internal textile structure onto which the outer rubber is applied. Many of the tyre’s dynamic characteristics stem from this: elasticity, comfort, protection and weight. Let’s look at the main aspects:

• TPI (Threads Per Inch): This indicates the thread count of the tyre casing. A high TPI (e.g. 120) means a lighter, softer and more responsive tyre. A low TPI (e.g. 60) indicates a sturdier, more puncture-resistant structure.
• Tire tread: Softer tyres offer more grip but wear out faster; harder compounds last longer but are more prone to skidding in the wet.

Compatibility with the frame and fork

Before you buy very wide tires, check their compatibility with the frame and fork. The space between the tire and the bike’s structure (known as tire clearance) should be at least 4–6 mm to prevent blockages from mud or debris. A tire that is too wide might literally not fit in the fork or could damage the frame.

Always check the manufacturer’s technical specifications or, if in doubt, measure the available space directly on your bike.

Common mistakes to avoid

1. Excessive pressure: Overinflating gravel tyres negates the benefits of the wide tread, making the bike unstable and uncomfortable.
2. Underestimating the terrain: Using slick tyres in the mud is dangerous; using extreme knobby tyres on tarmac alone is unnecessarily tiring.
3. Ignoring wear and tear: A worn tyre loses the properties of its rubber compound, becoming less safe and more prone to punctures.