Most off-road bicycle tires have "V"-shaped treads, while cars often have longitudinal grooves, which may not be very useful for off-road performance. The tire tread has a unidirectional slant, which is related to asymmetric drainage on one side. The part of the tire that contacts the ground is compressed, and if you analyze a specific shape on the tire surface, you’ll find a pattern.
The upper part of the "V" shape, when aligned in the same direction as the wheel’s forward rotation, makes contact with the ground starting from the "tip" first and then the "base." The tip, being pointed, guides the mud or water on the road surface in an orderly manner to its lower part. This is similar to the bow wave of a ship parting around its sides or the effect of airflow around an aircraft.
This process continues until the entire "V" shape is compressed, with excess water and mud being expelled outward. Upon lifting off the ground, the pressure decreases and the tire returns to its original state. Water and mud are drawn in from the outside through the channels formed by the "V"-shaped grooves and the ground. At this point, the "V legs" are still compressed and cannot fully absorb mud or water for a short time. As this process continues, there will be water or loose mud in the "V" grooves, which can be thrown off. Therefore, this direction is the typical drainage orientation.
If the lower part of the "V" shape is aligned in the same direction as the wheel’s rotation, the contact area, pressure sequence, and guiding effects all work in reverse. In this case, the pressure is significantly borne by the tip, creating an inverted "V" shape, and the drainage flows noticeably toward the rider. The internal pressure within the "V" groove becomes much higher. The faster the speed or the quicker the tire rotation, the faster this compression occurs and the greater the resulting pressure. On poor road surfaces with standing water or thick mud, the water or mud cannot be smoothly expelled, causing a noticeable increase in attachments on the tire surface. Essentially, the tire’s direct contact with the ground is isolated by a layer of water or mud. If the rider is moving too fast, this isolation layer can, due to inertia and centrifugal force, lift the entire tire, causing a loss of friction and potential skidding or accidents. In short, installing the tire in the reverse direction may pose some risks.
However, for special road conditions—such as thick, muddy terrain—reverse installation can actually provide better grip. (Cyclists who have traveled the Qinghai-Tibet Highway have encountered such situations, where large trucks get stuck in deep mud. On these long, thick muddy stretches, the tire must rely on its tread pattern to grip the mud, and simply accelerating the throttle only makes things worse.) So, when traversing such surfaces, don’t expect to push the mud and water out—instead, rely on the tread’s contact and bite with the mud, using the advantage of "gripping the path" to achieve satisfactory passability. (For the rear wheels of bicycles, this reverse installation method clearly has significant advantages.)
Taking Michelin’s standard off-road tire model, the Michelin Wild Gripper COMP, as an example—if translated literally as "wild gripper," it primarily emphasizes this aspect.
For bicycles, if using the second installation method, it is suitable for extremely thick soft soil layers. Generally, the first method is preferable for everyday use.
Because tire treads vary greatly and serve different purposes, this article only discusses some off-road tires. Feedback and corrections are welcome.
Choosing Tires by Thickness
Thicker tires increase grip but also add resistance and weight. Thinner tires reduce resistance, making them smoother on flat roads, but with weaker grip. Even with the same block pattern, different thicknesses result in varying performance.
Thick Tires (2.25~2.0)
On hard surfaces, they provide cushioning and grip. On soft surfaces, they reduce tire sinkage. However, weight and resistance increase, making them suitable for more physically capable riders.
Medium-Thick Tires (2.0~1.9)
Offer stable riding on streets.
These are typical sizes for mountain bike tires.
Thin Tires (<1.9)
Reduce road resistance, making them suitable for stable street or road riding and resisting impacts from hard surfaces.