Let's talk about gravel tires, to understand well what tires to mount and when according to our needs.
The tires are the point of contact of the bike with the ground. They allow you to release the propulsive force to the ground and to have grip to face the curves; they also give us grip when braking and, last but not least, absorb the roughness of the ground by dampening shocks and vibrations.
Perhaps, gravel is the sector where developing a quality tire is more challenging because it must perform well all the tasks required on various types of terrain. It must be smooth on the road and allow a good grip on asphalt (even wet) but have a tread suitable to deal with dirt roads and ensure grip when cornering and braking, have a carcass that allows a good rolling but sufficiently resistant not to cut the rubber on the first stones. In short, the tires on gravel bikes must be the right middle ground to meet our needs, which is not an easy task.
We can distinguish gravel tires in two main categories:
- Slick tires for hard ground
- Knobby tires for mixed terrain
Another difference is the wheel size: 650b wheels and 700c wheels have different characteristics and different advantages and disadvantages, which will be reflected on the use we are going to do.
Then, let’s analyze the individual categories to understand when and where to use one type rather than another according to their characteristics.
Slick tires for hard ground
This type of tire features a closer and lower central knob design, in order to improve the rolling qualities (even on asphalt) and to ensure a good grip on hard and dry dirt roads. They are excellent on terrain such as dirt roads, fairly even and even dusty. They roll well on asphalt and provide good grip even on wet asphalt. The low knobs allow a large area of contact with the ground so as to have good traction and grip even when braking. Let’s say that they are the perfect tires for the summer if we ride mainly on this type of terrain; in winter, they have some limits on wet dirt roads, even if they are smooth. Anyway, usually there is a good side tread that assures a very good grip in curves on dirt roads. Generally speaking, their casings are a little lighter and less protective, but there are exceptions. For the weight freaks, they are lighter than the most treaded tires, due to the smaller amount of rubber; however, it is a few grams of difference.
Knobby tires for mixed terrain
These tires feature a significant tread pattern that allows the rubber to penetrate the ground and guarantee grip even on the most difficult terrain such as mud, sand, loose soil and grass. The shape of the knobs is very important as is their spacing. A knob transverse to the rotation direction allows a great grip in braking but lowers a lot the smoothness; on the other hand, a knob longitudinal to the rotation direction, if well made, allows a good grip and a good smoothness, the right middle ground that a gravel bike needs. The spacing of the knobs is particularly important in muddy terrain to ensure a good removal of mud and keep the rubber clean so as to ensure grip at every turn. Therefore, a good compromise is to have central longitudinal knobs more closely spaced, in order to have good grip and good smoothness even on asphalt, and more spaced and prominent side knobs so as to allow the rubber to penetrate the ground, especially in corners, and to clean itself well from the mud and the ground in general. These tires are usually a bit heavier. They are the ideal choice for mid-season and winter, or for when we want maximum versatility and peace of mind in dealing with all types of terrain. On asphalt, they suffer a bit in terms of smoothness, but they are appreciated when we have to deal with turns on dirt roads.
The size matters: 650b or 700c?
When it comes to wheels and tires, size does matter. If in the MTB sector a balance has been found between 650b and 29″ after years of keyboard battles and hand chronometer comparisons, in the gravel sector, fortunately, the phase of battles over what is better or worse has been skipped over. In fact, the two diameters offer different advantages and disadvantages and each one is better for certain situations and has its own field of application.
How come? Simply because the actual diameter in the end becomes almost the same; what changes is the volume of the tire and its section.
Let’s try to explain better: the tires that are usually mounted on 700c wheels vary between 34/35mm section up to 40/42mm, those that are mounted on 650b wheels range from 42/45mm up to almost MTB sections. It goes without saying that if the section increases, the final diameter of the wheel increases, so they are very close to each other in absolute terms of diameter.
Therefore, a 650b tire has a larger volume, a larger trace and usually a heavier weight. Consequently, we can ride at lower pressures with more comfort and grip, but on the other hand it will be less smooth and generally less fast. In short, it is a tire more suitable for those who pedal most of the time on trails and technical terrain.
With the same type of tire, a 700c tire will have a smaller trace and a lower weight, being consequently smoother, faster and quicker even in changes of pace. Also in downhill on asphalt, a smaller volume represents an advantage in terms of drivability. The main disadvantages are the lower comfort due to the lower absorption and the higher pressure required as well as a lower grip. It is a tire suitable for those who pedal more on fast and smooth terrain or who cycle a lot on asphalt in addition to dirt roads.
The various merits and demerits can be mitigated by adopting various types of rubber: for example, if we mount a smoother rubber on a 650b or if we mount a more treaded one on a 700c to increase grip on mixed terrain.
There is no ideal tire for everything but there are various choices based on our needs. Today, the market offers a wide variety of gravel tires that allow you to tackle any route safely and having fun. Our advice is to choose quality and reliable tires, with designs, compounds and carcasses specific to the gravel and the terrain that we are going to face to a greater extent, whether dirt roads and smooth as the white roads or mixed technical trails. Pay close attention to the design of the knobs and choose the size of the tire and wheels based on the characteristics you want, remembering that more volume corresponds to more grip and comfort and less volume to more speed, precision and lightness. Which is the most suitable tire for the Tuscany Trail? We’d say that a treaded tire for mixed terrain, like the Pirelli Cinturato Gravel Mixed Terrain, is the best choice for tackling the trail safely and with maximum grip, in both wheel sizes!