27.5" vs 29" tires for mountain bikes: Which one to choose?

For years, tire size was not something most mountain bikers considered when choosing a bike. This was because all mountain bikes came with standard 26-inch tires. Then came the other two tire sizes. First on the scene were 29-inch tires, followed later by 27.5-inch tires (also known as 650b).

The right size for you largely depends on what you want to get out of your mountain bike and the type of terrain you want to ride on.

Comparison of 27.5" vs. 29" Mountain Bikes:

The best way to learn the differences between 27.5" and 29" bikes is to experience them yourself. Take each for a test ride and feel the differences.

1. Acceleration

27.5" have faster acceleration, while 29" are more efficient at maintaining higher speeds.

Smaller tires accelerate faster than larger tires. This is mainly due to where the weight is distributed. Larger tires place the weight of the spokes, tires, tubes, and rims further inward from the wheel center, resulting in greater rotational mass and slower acceleration. When you reduce the rotational mass of a rolling object, it spins faster and more easily.

27.5": Faster acceleration is often seen as one of the biggest advantages of the 27.5-inch wheel compared to the 29-inch wheel.

29": Wheels that accelerate more slowly take longer to reach high speeds. However, once 29" bikes reach top speed, they are actually more efficient at maintaining that speed than smaller 27.5" bikes, as they require less effort to keep their momentum. Another downside is that you need to slow down earlier before entering a turn compared to 27.5.

2. Grip

Due to their larger surface area, 29" tires have better grip.

27.5": These tires provide very good grip and are suitable for most purposes and trails. Other considerations, such as acceleration or weight, may ultimately be more important factors when choosing wheel size.

29": These tires, with a larger contact patch (9 cm), may be the best choice if you will be riding mountain trails with slippery obstacles.

3. Angle

29" overcome obstacles more easily.

Smaller angle is better because the wheel can roll over an object more easily.

27.5" do not overcome obstacles as easily as 29s.

Consider where you will ride: if you will ride on smooth trails, 27.5-inch tires will serve you well. For obstacles you encounter on the trail, it’s better to choose 29". Many riders feel more confident with larger tires.

4. Weight

27.5" are lighter. Bikes with 29-inch tires can weigh about 2 kg more than bikes with 27.5-inch tires. The weight of your bike is important depending on your type of riding.

If you are a recreational rider: The weight difference between 27.5-inch and 29-inch tires may not be your biggest concern. You might be more interested in grip and angle.

If you are a professional cross-country rider: You will likely look for ways to reduce weight. Racing on a bike with smaller diameter tires will reduce bike weight, but this is not the only way. You can also look at the material of your frame, handlebars, seat, or tires.

Using tubeless tires is another great way to reduce weight. Tubeless tires do not always reduce the bike’s weight, but they noticeably improve tire grip on terrain at the same pressure and reduce the risk of punctures.

5. Maneuverability

Bikes with 27.5-inch tires are more maneuverable.

A 29-inch bike is more flexible due to the frame extension that comes with the larger size for this type of bike. With such a frame, the bike turns more easily in tight corners.

If you regularly ride tight and narrow trails, you may prefer the feel of a 27.5-inch bike. The 27.5-inch tires retain much of the feel of the original 26-inch size, as well as many of the advantages that come with the larger wheel.

29-inch bikes overcome obstacles more easily, as you can roll over obstacles like roots, rocks, or other objects instead of trying to quickly maneuver around them.

6. Suitable for

29-inch tires are often more suitable for taller riders.

The larger 29-inch tires affect the overall geometry of the bike frame more drastically than 27.5-inch tires. This can make it harder for shorter riders to find a 29-inch bike that fits well with their height. Try both sizes if you can to best assess.

Taller riders may prefer the feel of a 29-inch bike. However, a 27.5-inch bike can also be suitable for tall riders, so decide what your priorities are – acceleration, traction, and/or angle.