For a while, all mountain bikes came with standard 26 in. wheels.
Now, they come in two wheel sizes that have, for the most part, overtaken 26 in. wheels. First on the scene were 29 in. wheels (29ers), followed a few years later by 27.5 in. (also known as 650b) wheels.
The right size for you largely depends on what you’re looking to get from a mountain bike and the type of terrain you love to ride.
Come take a test ride! A good way to learn the differences is to feel them for yourself.
27.5 in. wheels have faster acceleration while 29ers are more efficient on longer rides.
Smaller wheels accelerate faster than larger wheels.
27.5”: Faster acceleration is often cited as one of the biggest benefits of a 27.5” wheel when compared to a 29” wheel. Wheels that accelerate faster will give a bike a more responsive feel that many riders desire.
29”: Wheels that accelerate slower take longer to get up to speed, possibly giving the bike an unresponsive feel. Although, once the larger wheels reach top speed, they’re actually more efficient for longer rides because it takes less effort for them to keep their momentum going
Because of their greater surface area (aka “contact patch”), 29 in. wheels have better traction (when comparing comparable tires).
27.5 in.: These wheels provide very good traction and are good for most purposes. Other considerations, such as acceleration, weight and fit may ultimately be more important factors in your choice of wheel size.
29 in.: These wheels, with their larger contact patch, may be your best choice if grip on slippery rocks and roots is a top priority.
27.5 in. wheels are lighter.
There’s no way around it; a larger wheel is heavier. Bikes with 29 in. wheels can weigh about 2 lbs. more than bikes with 27.5 in. wheels due to more wheel material and more tire rubber.
Depending on the type of riding you do, the weight of your bike may or may not be very important.
If you’re a casual rider: The weight difference between 27.5 in. wheels and 29 in. wheels may not be your biggest concern.
Setting your wheels up to be tubeless is another great way to reduce weight. Tubeless wheels not only reduce overall bike weight, but they also accelerate faster.
27.5 in. bikes are more maneuverable.
A 29 in. bike is more flexible due to the elongation of the frame that comes with the larger wheel size. This can result in a bike that feels harder to handle in tight turns.
If you regularly ride the twisty and turny trails you might prefer the feel of a 27.5 in. bike.
29ers roll over obstacles more easily, so you may find you’re able to go up and over rocks and roots rather than trying to quickly maneuver around them.
29ers are often better suited to taller riders.
The larger 29 in. wheels affect the overall geometry of a bike frame more drastically than 27.5 in. wheels. This can make it difficult for shorter riders (especially those shorter than 5 ft. 6 in.) to find a 29er that fits well. Test ride both wheel sizes if you can.
Taller riders, especially those over 6 ft. tall, may prefer the feel of a bike with 29 in. wheels. However, a bike with 27.5 in. wheels can also fit tall riders well, so we'll let you decide what you like best!
Shared from REI