Mountain bikes are great for exercise while connecting with nature. Unlike regular road bikes, mountain bikes have thicker tires, more suspension, and an upright cycling position. There are multiple sizes of tires you can choose from that can help enhance performance.
Can you put thinner tires on a mountain bike? It is possible to put thinner tires on a mountain bike, but narrow tires have less cushioning, which means that they cannot absorb as much shock from rocks, curbs, and cracks. The typical mountain bike rim has a minimum tire width of 28mm.
The wheels on a mountain bike are what keeps you moving and will have an impact on the quality of the ride. When deciding what size tire to use for your mountain bike there are several things to consider. Tires should match your riding style, terrain, and preferred riding discipline.
What Size of Mountain Bike Tire Is Considered Thin?
Bicycle tires have a couple of important numbers, measuring both the diameter of the wheel and the width of the tire.
Tires come in three diameters, 26”,27.5”, 29” and a children’s 24”. Here is a little more about what those measurements mean.
- 26” – When mountain biking came about, all-mountain bikes came equipped with 26” wheels. Although there are now more tire options, the 26” is still a popular choice due to their responsiveness and maneuverability.
- 27.5” – This is a good mix between the 26” and the next size up. They are easier to roll over terrain as the 26” while more maneuverable than the 29”.
- 29” – These larger wheels are heavier and a little slower to accelerate, but once they get moving, they can cover more terrain than a basic 26” tire. They offer more grip and a higher attack angle, or the ability to roll over trail obstacles easier. This is the more popular size tire for cross-country bikers.
- 24”- These tires are for children mountain bikes. They accommodate kids’ shorter legs. Typically, suitable for children ages 10-13.
Along with the tire diameter, tires also have the width to put into consideration. Each width is used for a different style of mountain bikes.
- Cross-country bikes: Tires in the 1.9” to 2.25” width range.
- Trail and all-mountain bikes: Tires in the 2.25” to 2.4” width range.
- Downhill bikes: Tires up to 2.5” width and meant to withstand drops and rocks.
- Fat bikes: Tires in the 3.7” to the 5” plus width range, which is an all-season trail riding bike.
Wider tires are heavier and provide better traction, which is perfect for sandy areas. You can put wider tires on a current rim or get a wider rim that can accommodate an even wider tire.
Benefits of using a wider tire include:
- Better traction
- Rolling resistance
- Ride quality
- Air volume
Mountain Bike Rims
The rim sits on the outside of the wheel, and its main function is to hold the tire. The width of the rim will affect what width of the tire you can use, which can affect rider control and grip.
The average internal width of a tire rim is between 21-25 mm, while a larger rim is considered 28mm.
For mountain biking, it is more beneficial for the rims to be wider. Wider rims result in an improved comfort through greater tire air volume. Greater tire air volume coincides with using larger tires, which improve roll-over ability, traction, and control.
The depth of the rim affects the lateral stiffness of the wheel, which is how well a wheel resists flexing sideways.
These offer significant aerodynamic drag benefits over traditional shallow rims. Having more aerodynamics helps the rider go faster with the same effort or the same speed for less effort.
Deeper wheels may be beneficial, but they do have some drawbacks. Bikes with deeper wheels may make the rider feel more susceptible to crosswinds because they will typically generate more side force than a shallow wheel.
Deciding on having deeper rims depends on what your riding style is. If you’re planning on doing time trials, crits, and road races, then a deep-section wheel is beneficial.
Choosing Mountain Bike Tires by Riding Style
Whatever type of tire you choose will depend on the riding style you prefer. There isn’t a tire that covers all your needs, so it is important to focus on the attributes that are most important for your choice of riding style.
Trail riding bikes will have a more all-around tire that gives a moderate level of traction, durability, and speed.
- Equipped with the 27.5” sized wheels
- Suspension can be anywhere from 4.7” to 6” of travel
- Neutral head angles
- Tires will have a balance of durability, traction, and rolling efficiently
Because the main vision of all-mountain biking is actually the descend down a mountain, tires need to be able to grip well when taking turns at high speeds, as well as tires that can withstand moderate impacts.
- Equipped with the 27.5” sized wheels
- More suspension travel from 5.5” to 6.7.”
- Head angles in the 65° to 67° range
- Good for cornering and traction
Downhill bikes are designed for steep terrain, speed, big drops, and jumps, so you’ll need tired that can withstand abuse and stick landings.
- 27.5” wheels
- 6.7” to 10” suspension travel in the rear and 7” to 8” suspension travel in the front
- Low center of gravity with 65° head angle
- Tires are equipped with 2-ply casings and a full spiked tread pattern to get good traction and durability
Because cross country is for climbing efficiency, you’ll want tires that are lightweight and can roll fast. These bikes are made for endurance and efficiency.
- 29” wheel
- Ultra-lightweight with 4.7” or less travel
- Longer chainstays and wheelbases, steep head angle and longer stems
- Reduced weight, efficient, and faster rolling resistance rather than traction, control, and durability.
Difference Between Mountain Bikes and Road Bikes
Mountain bikes and road bikes both have the goal to help you reach a destination, but they have different qualities that set them apart from each other. The main difference is that they are used on different terrains.
Road bikes shouldn’t be used for trail rides as mountain bikes shouldn’t be used on the road. (More on that topic here).
- Used on smooth terrain like well-maintained pavement
- No shocks/suspension
- Smooth and skinny tires that lower rolling resistance
- Light frame
- Rides less upright for wind resistance
- Used on rough terrains like trails and mountains
- Full suspension for dealing with jumps
- Wider tires that help with traction in rough terrain
- Heavier frame
- Rides more upright for visibility and weight shifting
How Tire Tread Affects Performance
The design of the lugs on mountain bike tires varies widely. Understanding the differences treads and other tire features will help you match your tires to your riding style.
- Large, widely spaced lugs are good for soft, muddy ground. The wider channels make it possible to ride in and out of muck without getting sucked in.
- Small, closely spaced lugs offer a modest grip with a low rolling resistance, which helps with speed.
- Ramped lugs are typically placed in the center, slanting towards the rear and creates a lower rolling resistance that helps with speed
- Side lugs are typically bigger and provide more grip in the corners
- Transition lugs are located between the center and side lugs. They increase the grip as you lean into a turn, which creates a smooth transition from center lugs to the side lugs.
- Sipes are slits within the lugs that help them have a stronger grip on hard, slick surfaces.