Mountain Bike Tires Explained!

maxxis tires

You would think that choosing the right set of mountain bike tires would be an easy choice but can be a surprisingly tough decision! There are so many factors to consider to ensure that you’re picking the right set of mountain bike tires for you. We look at some of the factors that are important for picking the right mountain bike tires? While there are many options, the most important ones to consider when selecting mountain bike tires are where you ride, how you ride, and your type of bike. These answers will impact your decisions for a specific tire diameter, width, and tread pattern.

Mountain Bike Tire Tread

Now that you understand the ins and out of tire size and diameter, it’s time to look at the next most important – tread. In addition to tire width, the tread on a bike plays a crucial role in determining it’s rolling efficiency, grip, and stopping power.

While tread may seem like a simple subject, it’s actually quite the science these days. From knob size, spacing, placement, directionality, etc… there are a lot of options when it comes to tread!

Tread characteristic #1 – Knob Size & Shape

Knob size and shape.

One of the first and most visually obvious components of the tread is its knobs. The shape, height, and size of knobs all factor into how much grip, braking power, and rolling resistance that it creates with the ground.

In general, smaller and shorter knobs are better for hardpacked surfaces because they provide adequate grip without slowing down the rider. They minimize the rolling resistance and allow for more efficient travel. However, they also provide less braking power compared to larger, more aggressive knobs.

Medium sized knobs will provide better bite for softer surfaces, while large knobs provide the most traction and are best suited to downhill riders or when trails are extremely slick and/or loose.

Just like the variety of sizes, knobs come in many shapes. From square to round, tapered and ramped, to darts and chevrons they all have an impact on performance.

  • Square knobs have more bite compared to rounder knobs but create more rolling resistance.
  • Knobs can be tapered so that they’re larger at the bottom than the top. These are perfect for really soft surfaces and prevent the tires from being clogged with dirt and mud.
  • Ramping is a directional design that creates less rolling resistance while also increasing the tire’s braking power. It does this by using a smooth shallow front angle to the knob, combined with a steep back angle. This allows for smooth rolling while moving backward but quickly bites into the ground when applying the brakes.
  • Darts and chevrons are horizontal pieces that create additional edges for enhanced turning efficiency.

The size and shape of knobs is only part of the equation, so let’s jump into their spacing i.e. pattern to see how it also plays a role.

Tread characteristic #2 – Pattern

Left: A cross-country tread pattern. Right: An aggressive downhill tread pattern.

As can be seen in the comparison photo above, there can be a big difference in the tread patterns of tires. The left tire is a cross-country focused one, and in addition to it’s smaller knobs it has a tighter tread pattern. The lack of spacing between the knobs allows it to glide more smoothly across the ground with less rolling resistance.

The tire on the left is a classic downhill tire that has large knobs and wide spacing. This spacing allows the knobs to bite into the ground and provide more grip. It also allows the tire to shed loose material like mud instead of it getting stuck and caked into the tire tread.

Tread zones

Aside from the general spacing and distribution of the tread, there are three key zones that tire manufacturers focus the tread around. These key zones are the center, transition, and side.

Mountain bike tire tread zones.

Most of your riding time will be spent engaging the center zone of the tread. This occurs when you’re riding in a generally straight line, with minimal leaning. Because this area of the tread accounts for a large portion of its surface area, it greatly affects the overall rolling resistance, straight-line traction, and braking power.

Small knobs with close spacing of the tread throughout this zone can help to lower the tire’s rolling resistance but do come at the sacrifice of slightly less traction and braking power. This setup works great for hardpacked surfaces, but when the trail becomes softer or looser you’ll want larger knobs with more spacing between them.

On each side of the center zone, you can find the transition zone. These play a role to help the bike maintain traction when it’s at a moderate lean angle. The more knobs that are in this zone the better its traction will be. As always, that increased traction does come at the cost of more resistance i.e. less efficiency.

The side zone comes into use during cornering where the bike is more sharply angled. These are usually larger in size compared to the center or transition tread to ensure maximum traction in these situations. Efficiency loss is less of a concern in this zone as the total time spent using them is far less than the others. Not to mention that the alternative of slipping and crashing in a turn would certainly not be a good outcome!

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