Selecting the right mountain bike tyres is more complex than ever. With more brands offering a growing range of tread patterns, casings, and rubber compounds, choosing the best option can feel overwhelming. To simplify the process, we sat down with Aaron Chamberlain from Maxxis North America to talk about all things tyres to untangle the key factors in choosing the right tread, casing and compound for your bike and terrain.
While what we cover in this article is spoken in the language of Maxxis, everything is still relevant to any other tyre brand and can be easily translated to Schwable, Continental, Michelin or Specialized.
Before diving into specific considerations about how to choose the best mountain bike tyres for you, let’s do some jargon-busting and run through the anatomy of a mountain bike tyre, as understanding each of these terms is foundational to choosing the right option.
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The anatomy of a mountain bike tyre explained
Which part of the tyre is the bead?
The basis of every tyre is the bead, it’s what locks the tyre into the rim and holds everything in place. Chamberlain likened the function of a tyre bead to a spine, as it’s the main structure that holds everything in place.
It comes in two types: wire and folding. Wire beads are stronger but heavier and more challenging to put on a rim. On the other hand, a folding bead is lighter and more pliable, making these tyres easier to install. As a result, folding beads are the most common choice for modern MTB tyres.
How do I know which mountain bike tyre casing to choose?
Keeping in the same metaphor, Chamberlain described the casing as the rest of the tyre’s skeleton. Casings, made from nylon threads and form the structural foundation of the tyre. There are different types of nylon and thread counts, also known as threads per square. Mountain bike tyres also come in single-ply and dual-ply, and the casing is where you’ll find the puncture protection. Stay tuned for a more in-depth explanation of what all this means below.
What are the different compounds used for mountain bike tyres?
The compound refers to the rubber formulation — something tyre brands keep as a closely guarded secret. While tread patterns can be copied, a tyre’s compound is what truly defines its trail performance
What’s a tyre tread pattern?
This refers to the layout, shape and size of the tread/ knobs on a tyre. Generally tightly packed knobs create a faster-rolling tread, while larger, widely spaced knobs excel in technical terrain, offering better traction on rocks, roots, and muddy conditions. Though taller knobs perform well in mud and loam, they can squirm or fold over on hardpack and rocky terrain. So, selecting the right tread pattern for your location, trails and, in some parts of the world, season is essential.
Oh, So Many Variables | How to choose mountain bike tyres
Selecting the right tyre is all about balance and taking into account where you live and ride, as well as what you want from a tyre. There is no such thing as a free lunch, and depending on where you want a tyre to excel, there may be some concessions in other areas to achieve your desired characteristics.
“For cross country, weight and rolling speed are going to be the primary factors, and they (XC riders) are going to be willing to sacrifice other performance characteristics to get the best rolling speed and lowest weight,” Chamberlain explained. “For trail, you’re looking for a Goldilocks scenario; you’re going to want more traction than an XC race tyre, but also something faster than a full-on gravity tyre.”
That middle of the road will encompass rolling speed, braking traction, cornering traction and something with a bit of puncture protection, but not so much that it could survive a nuclear blast.
“For gravity riders, you want durability out of the casing, stability out of the casing, and then braking and cornering traction out of the tread design and rubber compound,” continues Chamberlain.
The trade-off for these characteristics is weight and rolling speed, as the thick casing that stymies sharp rocks and provides support is heavy, and sticky soft rubber rolls slower than its harder counterparts.
TPI, Ply and Puncture Protection | Understanding a mountain bike tyre casing
The casing is like the tyre’s skeleton, and MTB tyres have either a single-ply or dual-ply casing. This refers to the number of nylon layers stitched into the tyre.
Closely related to this is the number of threads per square inch (TPI), some single-ply tyres may have a higher TPI than a dual-ply tyre. This will all depend on the specific application the tyre is designed for. For example, one version of Maxxis’ premier XC tyre, the Aspen, uses a single-ply casing with 120 TPI—the same thread count found in some dual-ply tyres. There is also a race-only “Team Spec” version of the Aspen that sees a super supple 170TPI casing, but it’s quite fragile.
The type of nylon and thread count directly impacts a tyre’s ride quality and durability. A higher TPI tyre will see finer threads, which can be packed more closely together and generally create a more supple casing that can better conform to the ground and reduce weight. However, high thread count casings are often more susceptible to cuts and punctures. A lower TPI casing will be a bit stiffer because the threads are a higher gauge, and there is more rubber holding them together. Those wider threads are also a bit more robust, and the tyre will be heavier.
Many brands add protective layers over the casing to enhance puncture resistance. Maxxis, for example, applies a cut—and abrasion-resistant material layer to the sidewalls of its EXO tyres. As you step up the ladder of protection to the EXO+ casing, Maxxis adds a butyl insert around the bead of the tyres to enhance puncture protection further. Double Down and DH casing tyres take the butyl but see two layers of nylon fabric — in 120 TPI and 60 TPI respectively.
While the casing is where you find the picture protection, some opt to further fortify their setup with a tyre insert. Inserts do provide extra rim protection and sidewall support, especially when cornering hard or smashing through rock gardens. Just like choosing which tyre to run, adding a tyre insert is a compromise. While you gain the added protection, you are also adding some significant weight to your wheels.
Deciding whether to use inserts comes down to personal preference. They can be a nice insurance policy if you are a heavier rider with a history of cracked rims or you have an expensive wheelset you’re not mega keen to smash into rocks. Before you do go down the insert route, Chamberlain recommends stepping up to a more durable casing.
“Going to a more durable casing, you’re going to get better sidewall support, better damping, and you’re going to gain less weight than adding an insert in most scenarios. You’re also removing some of the complications with the installation of an insert and also having to deal with a sealant-covered pool noodle if you do get a flat out in the backcountry,” he says.
A Compounding Dilemma | What rubber compound do I want for my mountain bike tyres?
A tyre compound is where brands can make or break a tyre. Most companies won’t give too much information away when discussing what goes into each compound as the different additives used are what make the tyres soft and grippy or firmer and harder wearing. The unit of measure here is durometer or shore durometer, though, like the 11 secret herbs and spices that go into a particular compound, you won’t often find brands listing the durometer of a given rubber either.
The majority of Maxxis tyres utilise a version of the brand’s triple compound (3C) technology, though the new MaxxSpeed is actually a single durometer of rubber as, according to Chamberlain, the new formulation rolled faster, has better-wet weather grip and a more consistent wear rate. Some other brands, like Pirelli, only use a single compound in its tyres, citing more consistency across the life of the tyre.
Brands will change the thickness of each compound depending on the desired outcome. The compounds are also closely linked to the different tread patterns. You won’t find a 3C Maxxgrip Aspen, nor does Maxxis produce the Assegai in MaxxSpeed.
Maxxis also offers a less expensive Dual Compound rubber that sees a harder rubber through the middle tread and a slightly softer compound through the shoulders.
Chamberlain’s advice to riders was to spend some time learning what compounds are offered by the various manufacturers and take into account the type of terrain you’re riding.
“If you’re riding in the desert, maybe you don’t need the grippiest rubber compound. It’s going to roll slower and wear faster if you’re just ridding rocks all day long, and it’s just costing you money,” he says.
“Where I live, we have distinct seasons, and during the winter, I throw on griper stuff when it is really wet, and during the summer, I can put on a dual compound to get a little bit of rolling speed and better durability,” Chamberlain continues. “Ask a local shop for advice if you’re not sure.”
Tread Patterns Decoded | How do you choose the right mountain bike tyre tread pattern?
The shape and arrangement of the knobs make up the tread pattern, and once you get an idea of what different configurations do, you can apply this knowledge to whichever tyres you are looking at. The first consideration to take into account when you’re staring down the tyre wall at your local bike shop is what type of riding you plan to do.
“Generally, a denser tread pattern is going to roll faster. If you look at a cross-country tread pattern, it tends to be very densely packed with a low tread height. So it’s giving you a continuous surface to roll on, which is all about, reducing your rolling resistance,” he explains.
The drawback to this design is that it’s excellent in dry conditions, but not when it gets wet and muddy. If your knobs are super close together, they pack up easily with gunk.
A slightly more aggressive trail-focused design will be somewhere in the middle.
“You’re going to have medium-height knobs and medium tread spacing. These knobs will be a little bit further apart. You want good rolling speed and a little bit more traction than you would with a cross-country tyre,” says Chamberlain.
Stepping up to tyres with a gravity focus, the side knobs get bigger again and tend to spread further apart.
“That’s all about more traction and better cornering and braking. Obviously, there’s some trade-offs there, mainly being your, your rolling speed at that end of the spectrum,” Chamberlain says.
Another critical aspect of choosing the right tread is understanding what different tyre knob shapes are used for and the characteristic they have on the trail.
“If you take a tyre like our Minion DHR and look at the centre knobs on that, they’re really broad. They’re really wide knobs, and the back edges are just straight across, that’s your breaking edge,” Chamberlain explains. “So that’s giving you a really strong braking bite. It has a really large, continuous braking edge that also gives you good traction going up technical terrain.”
“On the XC/trail side of things, they’re smaller square knobs, that will punch through dry leaves and that little top layer of dirt.”
Chamberlin goes on to explain you won’t see many rounded knobs in a gravity context as that square shape helps with soil penetration so it can dig in and grip. However, you may see ramped leading edges to help reduce rolling resistance a bit.
There are also hybrid shapes, like chevrons or the infamous Ls on the edge of a DHR II.
“These are kind of a hybrid to try and blend the braking and traction performance aspects of a paddle knob, but you’re getting a little bit more of the ground penetration of a square knob,” Chamberlain says.
Bigger is not always better, just like there is a trade-off when choosing XC tyres that have smaller tread patterns. At the other end of the spectrum, tyres with tall, widely spaced knobs can tend to fold or squirm around when pushed into hard-packed trails.
An example of this would be the Maxxis Shorty. It has tall knobs that are widely spaced out; in wet and muddy conditions, this tyre thrives. However, when things dry up, and speeds get faster, the taller knobs tend to twist and wriggle around, making it harder to dig into the trail and can cause the bike to move around more at inopportune times. The taller tread design adds more rubber to the tyre, which in turn also adds more weight.
Knob deformation isn’t always a bad thing, and in fact, it’s built into a fair section of most tyres. The cuts and grooves in a tyre knob are called siping and are there expressly for the purpose of helping the knob deform in a specific direction to generate grip.
“It’s basically increasing the surface of the knob and its contact with the ground. It can be parallel to the direction of the trail, and that’s generally to help with leaning. If it’s split perpendicular to the direction of travel, that’s more climbing and braking traction,” Chamberlain explains.
Mix & Match| Why run different tyres on the front and rear?
Still, on the topic of tread patterns, it is very common for riders to run different tyres front and rear.
Usually, this involves running a grippier and sometimes wider tyre up front to keep the front end sticking to the trail and a faster rolling and sometimes narrower tyre out back. This mix-and-match approach can also be applied to the casings and compounds of each tyre.
“It’s pretty common for people to run a slightly lighter weight casing on the front compared to the rear because your weight distribution is usually more toward the rear, and most people don’t tend to smash their front wheel into things as hard,” he says.
Chemical VS Mechanical Grip | What the heck is the difference?
Chemical grip and mechanical grip are terms often thrown around in tyre reviews, and at face value, it’s not particularly clear what they are referring to.
When asked to explain the difference, Chamberlain passed it over to Maxxis Senior Design and Development Engineer, Sean Day.
“The main forces at play that correspond to what we perceive as the tyre’s grip can be simplified into a combination of a frictional force between the tyre and the terrain…When the tyre tread can sink into and penetrate into the terrain, the surfaces of the tyre and terrain that have some component of their geometry normal to the direction of the acceleration apply equal and opposite forces to eachother,” Day said.
“The first force is referred to as “friction” which you alluded to as chemical grip, and the second is “shear force” when discussing vehicle tyre dynamics in the company, but we can refer to the latter as mechanical force/grip,” he continued.
To break this down into simpler terms, the chemical grip is how the compound of the tyre generates friction on the surface (trail) that it is rolling over. This is where tyres with a harder compound will roll faster, as there is typically less friction between the tyre and the trail. Softer tyres will generate more friction and produce more grip on the same section of trail.
Mechanical grip refers to how the tread digs or bites into the trail surface. As the tread penetrates the ground, it provides a level of support and grip for the tyre. Both forms of grip work together, making it difficult to isolate their individual effects.
How much should I pump up mountain bike or gravel tyres?
Chamberlain stressed the importance of regularly checking tyre pressures. A big takeaway from our chat was to get a digital tyre pressure gauge and check your tyres regularly. Digital gauges are more accurate and easier to measure small pressure changes.
“Don’t rely on the gauge on your pump,” he said.
It would be great if there were a universal tyre pressure guide, but the reality is more complex. There are too many variables when it comes to setting your pressures, and what works for me, or Chamberlain might not work for you or your riding mates.
Complicating things even further, sometimes a few PSI can have a massive difference on feel and how the tyre performs.
“Everything is a trade-off. If you run higher pressure, you’re gonna protect the rim and tyre better…If you go too high, you’ll be pinging off obstacles. That’s going to be physically tiring and mentally taxing if your front end is just bouncing off of things,” he says.
Your weight, casing, the type of trails, and even the weather can all play a role in the pressure to run.
“If it’s really wet, and things are going to be slimy, then I know I’m going to be going slower. I can run lower pressure because I want more traction and a little more comfort. Then vice versa, in the summer, if it’s super hot and the trails are running fast, I can run a little bit more pressure, but we’re talking like one to two PSI either way,” he says.
In the same vein as with suspension, the only way to figure out what works for you is to experiment and tinker until you find the sweet spot. With that said, there are a heap of tyre pressure calculators out there that can provide you with a baseline from which to start. We’ve had good luck with the SRAM, Silca, and Wolftooth calculators.
Write down what pressure you are running and then complete a bracketing exercise, just like when setting up suspension, to determine if changes make the ride feel better, worse or the same.
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Tyre Width | Choosing the correct tyre width
There used to be a fairly large range of tyre widths available across the board. However, things have settled down now, and for the most part, the width of a tyre will be between 2.2in and 2.6in. With 2.4in and 2.5in being the most commonly used options.
Before selecting a tyre size, check your rim’s internal width, Chamberlain said anything from 25mm up to 35mm wide is going to work. His advice for riders looking for a new wheelset was that “you can’t go wrong with 30mm rims.”
Mismatched tyres and rim widths can create an overly square or round profile, affecting grip and handling. A wider tyre, like 2.5in, fitted to a 25mm wide rim will be too round, and if you had a 2.4in tyre on a 35mm rim, it makes for a boxy profile.
“If it’s too round, you have to lean the bike super far over to engage the side knobs. That’s where you’ll run into issues with cornering traction because the bike has to be leaned over so far that you’re already sliding along the trail on your face,” he chuckles.
“If it’s too square, then everything is in contact with the ground at the same time, and you’re on your side knobs already. It makes the corner really vague. If you’re already on your side knob, it makes it impossible to tell where the limit of it is,” he continues.
Nowadays, even the top XC World Cup racers now run wider tyres, with most racers opting for a 2.4in tyre. Wider tyres, which in turn have a larger air volume, allow riders to run slightly lower pressures, which can improve comfort and traction.
However, just like with most of the other factors to consider when choosing a tyre, wider isn’t always better. For riders who like to throw the bike around and are very playful on the trail, sometimes a slightly narrower tyre, like a 2.35, may be better suited to your riding style.
Maintenance Tips | How to help your tyres last longer
We asked Chamberlain how to best look after our tyres. His number one tip was to not apply anything chemical to them, including tyre shine products or strong cleaners. These can adversely affect the rubber compounds in a mountain bike tyre.
He also recommended taking the sealant out of your tyres if you are not going to ride them for a few months or more. This especially applies to riders whose trails are seasonal and may be closed during the winter months. Sealants will often have an ammonia compound that can accelerate your tyre’s deterioration.
Final Thoughts
Hopefully, you are now armed with a better understanding of the key features and characteristics of the design and construction of mountain bike tyres. Remember that selecting the right tyre or tyres is all about weighing up what you are hoping to achieve. Do you prioritise grip over weight and rolling speed, or is puncture protection high on your list of needs?
You will need to think about where you ride, the type of trails you like and how much the weather can impact these trails. Finally, ensure you have a digital tyre pressure gauge and check your pressures regularly.
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