Choosing the Right Mountain Bike Tires

The choice of right mountain bike tires is a subject that should not be taken lightly because it is a crucial safety element. A tire unsuited to the terrain or your practice can be catastrophic because the tire influences your way of mountain biking. It is indeed the only part of the bike which is in contact with the ground and which provides you with traction, steering, braking, and suspension.

Depending on your practice, the type of bike, the terrain, and the weather, the tires to choose are very different: structure, width, section, and pressure are key characteristics for a suitable mountain bike experience.

As much to say right away: There is no ideal tire for all situations. A tire well chosen for an outing at a specific time and place will not necessarily be suitable for the same outing at another time.

Identify the Type of Terrain You are Used to Cycling on

The type of terrain you are used to riding a mountain bike is the first parameter to consider when choosing tires.

The different types of terrain:

• Road
• Undergrowth
• Rocky or brittle

And the influence of the weather:

• dry ground
• Oily or muddy ground

If there are several types of terrain in the area where you drive, you will need to choose a versatile tire.

Let’s understand the parameters specific to Mountain Bike tires to make the right choices.

First of all, the tire must be compatible with your rim, and this is done according to several parameters :

Tire size

It depends on the size (diameter) of your rim; in mountain biking, three standards expressed in inches are standard:

• 26″
• 27.5″ (also rated 650B)
• 29″

They are suitable for 26″, 27.5″, and 29″ rims (″ = inches)

It will be more and more difficult to find tires in 26 inches, and the market is heading towards the obsolescence of this standard in favor of 29.

Tubetype, Tubeless-ready and Tubeless tires

Tubetype tires are intended to be fitted with an inner tube (conventional rims). Tubeless-ready tires can be fitted without an inner tube (only if your rim is tubeless compatible, i.e., sealed). The sealing of the tire is not total. Still, it can be ensured by a sealant or preventive anti-puncture introduced inside. Tubeless tires can be fitted without an inner tube (always if your rim is tubeless compatible). Sealing is guaranteed “by design,” At design, this implies a higher weight to guarantee increased solidity.

Adding preventive to a tubeless tire is interesting because, in the event of a puncture, the liquid will fill the air outlet: no need to stop to repair. A big advantage of tubeless is that it allows you to ride at lower air pressures, thus providing comfort and grip.

The Profile, or How to Analyze a Tire

The tire’s shape can provide much information about the type of practice and the conditions it can cover. In the same way, the inscriptions on the edges of the tires make it possible to obtain other information.

Section

The section represents the width of the tire, expressed in inches.

The section influences the type of use of the tire:

• A wide section will provide better comfort, improve cushioning, better protect the rim and give more grip since there will be more studs in contact with the ground.
• A narrow section can be inflated with more pressure and offer less rolling resistance. It is often synonymous with a light tire.

References: A section less than 2.0″ corresponds to a narrow tire. It’s written on the side of the tire next to the diameter. A tire with a diameter of 29″ and a section of 2.0 will, for example, be rated 29 x 2.0.

The Different Types of Studs and Their Impact

Large lugs provide more grip and more rolling resistance. They aim for softer terrain. Small lugs give less rolling resistance. They are smaller, so they use less material, and the tire will often be lighter. They aim for dry, compact terrain.

The less space between the lugs, the lower the rolling resistance. But the more the lugs are spaced out, the more the evacuation capacity of the tire is improved; this is an interesting profile for soft ground. Manufacturers often mix the types of studs to gain versatility: small studs on the tread and large studs at the ends. It allows good performance on the dry and compact ground while ensuring correct grip in turns.

Examples: The criteria can be mixed: A tire with large spaced studs will be appreciated for soft ground and even greasy ground since it will allow it to be evacuated more easily. A tire with short, close lugs will be perfect for dry/compact terrain and give less rolling resistance.

The Hardness of the Rubber

The hardness index or Shore A makes it possible to know the softness of the rubber which constitutes the tire. Soft rubber will have more grip than hard rubber but will wear out more quickly.

An index of 40 indicates a very soft rubber, 50 moderately soft, and 70 indicates a hard rubber.

Rigid bead or Flexible Bead

The beads are placed in the rim groove to hold the tire and create the seal between the tire and the rim for tubeless tires. Flexible rods often made of kevlar are lighter and can bend. Convenient to take a tire with you in Raids, for example. Rigid rods are steel-based and are often more economical but less convenient to store.

The Weight

The heavier a tire, the more resistant it will be to wear and tear. A light tire will be more fragile but will offer less rolling resistance.

Reinforced Sides

It is possible to have a stiffer and more resistant blank, especially if you want to ride with low pressure or downhill. Manufacturers use different techniques: specific rubber, double ply, and weaving… but this is done at the expense of weight in exchange for strength.

Weaving (TPI)

TPI = Threads Per Inch; this is the weave density of the carcass. The higher it is, the better the quality, and the tire will better adapt to the terrain. A thin carcass will make it possible to obtain a lighter tire. We can consider that the TPI index is synonymous with riding comfort.

From 100 TPI, it is considered the high range, and at 40 TPI, it is in the low range.

The Different Types of Profiles

Some examples of generic tire profiles adapted to different “classic” conditions or uses.

• Versatile: This tire allows you to roll correctly under any terrain; the studs are with medium spacing. On the tread, smaller lugs to limit rolling resistance and larger lugs on the edges for cornering grip.
• Muddy: The tire has a medium section (2.1 max) to avoid clogging and has large, wide lugs well spaced to evacuate mud.
• Dry: Small, short crampons, close together and numerous.
• Downhill (DH/Gravity): The grip must be impeccable and solid to avoid punctures, tears, and wear. Rolling resistance will be strong; they will be heavy. They have a big section (> 2.3) with large spaced lugs.

What Pressure Should You Inflate Your Tires to?

Now that you have chosen your tires, you still need to mount them at the right pressure. The generalization of tubeless has created a technological advance allowing to ride with much lower pressures than what is possible with tube-type tires. Let’s try to determine the optimal pressure for your tires.

The Benefits of Low Pressure

The tire and the ground area become larger as the pressure is reduced, allowing for more force and grip, whether by an ample contact patch or a greater stud count. The tire also can deform more easily, allowing it to hug the ground better and gain grip and comfort.

Admittedly, an over-inflated tire performs better in absolute terms (on the road!), but depending on the terrain, the answer is not so obvious. For example, there will be a flagrant lack of grip on uneven ground to tackle technical climbs. The discomfort generated by a tire bouncing over each obstacle will be disabling.

Factors to consider to find the ideal pressure:

Equipment

First, you need to know what type of material you are using. A tube-type tire or a tubeless tire?

In the case of a tire with an inner tube, low pressure greatly increases the risk of pinch punctures. The tubeless makes it possible to overcome this problem (although…), but be careful; under-inflated, the rim will absorb the shocks when the tire comes to heel.

Therefore, the tire’s stiffness and ability to support it vertically will impact the pressure you can use. A rigid carcass avoids the effect of blur on the supports by supporting the tire correctly while benefiting from the advantages of lower pressure at the tread level.

The more the tire is rigid, the more you can afford to lower the pressure

Then it is the volume of air that comes into play, and therefore it is the section of the tire that must be taken into account. A downhill tire contains a larger volume of air and higher sidewalls, so it is possible to inflate it less than a 2.1″ cross country tire, for example.

The bigger the tire, the more you can afford to lower the pressure on the rim before the end of the race.

Finally, the wider the width of the rim, the more it prevents the sidewalls from deforming. When cornering, the tread will be eccentric concerning the rim. A wide rim prevents the tire from temporarily coming out of the rim groove due to excessive lateral force.

With a wider rim, the tire deforms less laterally and helps to avoid coming off the rim.

Field

Rolling trails that have no obstacles allow the tire pressure to be lowered the most. The limit is generally found when a vagueness in the piloting is felt because of the tires.

On rough terrain, you have to ride a little more inflated; otherwise, you risk damaging the rims or pinching them. On greasy ground, we can lower the pressure a little to gain grip and compensate for the lack of grip on the ground.

Tip: Finding the right pressure on dry ground is a good start.

Last point, your level and your way of riding also influence the pressure. A quiet family outing will require less pressure than an aggressive outing with an experienced pilot who wants to go heavy!

In practice

Start with fairly high pressure (2.2 bar). You can also use the excellent online tool MTB Tech to get a starting pressure. Then, as the tests progress, descend little by little over the hikes, in steps of (0.2 bar), to find the setting that offers the best sensations. If you feel the steering becomes less direct and vague or hits the stones, go up 0.1 bar.

The rear tire is always more inflated than the front tire (about 0.2 bar difference) because your weight more stresses this tire.

How to Mount a Tubeless Tire Easily.

Fitting tubeless tires is not easy, so to help you, here is a procedure that works every time 💪.

Material required

• a tubeless tire (UST or equivalent)
• a tubeless valve (depending on the type of rims)
• soapy water
• a flat brush
• anti-puncture liquid + syringe
• a foot pump with a pressure gauge
• a strap about 2.5 to 4 cm wide and the length of the circumference of the tire

The procedure

1. Thoroughly clean the rim with soapy water, and remove the remains of anti-puncture liquid (liquid to be changed at least once a year and after each puncture!).
2. Fit the tubeless valve. Do not overtighten; above all, do not use tools (tweezers or other) to tighten.
3. Place the first sidewall of the tire (respecting the direction of rotation). Ensure that this first sidewall is at the bottom of the rim groove to place the second sidewall (all without tools).
4. Once the tire is completely retracted into the rim, brush soapy water with the flat brush between the tire and rim on both sides.
5. Place the strap flat on the entire rolling surface of the tire and tighten very slightly (do not crush the tire). 6. Start inflation with the foot pump; soap bubbles will form; that’s a good sign, and it’s time to remove the strap! Continue inflating to the tire’s maximum pressure (usually four bars). When inflating, you should hear clicks signaling that the sidewalls are rising in their rim housing.
6. Leave the tire to rest for about five minutes at four bars, then deflate it completely.
7. This being in place in the rim, it is now a question of filling it with anti-puncture liquid. To do this, unscrew the upper part of the valve (with the tool provided when purchasing the valve). Using the syringe, inject the required amount into the tire (see fluid manufacturer’s recommendations).
8. Replace the upper part of the valve, do not overtighten, and reinflate the tire to the desired pressure
9. Once the inflation is finished, put the wheel back on the bike and spin it empty to distribute all the liquid in the tire.

When to Change Your Muntain Bike Tires?

In a normal situation: Look at the studs on the tread located in the center of the tire. As soon as the lugs on the tread reach 20% of their original size, replace them.

The sides may show signs of weakness, especially if you ride on rough terrain. Look at them regularly to identify any cuts or deformations. If you detect cracks, abnormal deformations, or holes in the sidewall of your tires, then there is fragility, and you should consider replacing them.

Finally, for lack of adequate inflation, your tires may wear prematurely. Remember to inflate them regularly so as not to damage them because an under-inflated tire deforms, ages prematurely, and quickly shows cracks on its sidewall.