27.5 or 29 inch: MTB wheel sizes in comparison

There is a clear trend in MTB wheel sizes: 29-inch wheels over 27.5-inch wheels across the board. But 29-inch bikes aren't for everyone. We've spelled out the pros and cons of larger wheels.

Until a few years ago, choosing the right wheel size was easy. There were only mountain bikes with wheels in 26 inches. But 26-inch MTBs are slowly dying out. The major MTB manufacturers have not been developing new mountain bikes in 26 inches for several years. Even for downhill bikes, the 26-inch standard has had its day. 27.5 inches is the new 26 inches. Only in children's and youth bikes and in the second-hand market you can still find mountain bikes in 26 inches (559 mm).

To achieve more traction and better rollover behavior, the bike engineers equipped the new models with 29-inch (622 mm) wheels. But some bikers lacked the agility of the small wheel. To combine the advantages of both worlds, there were soon wheels with a size of 27.5 inches - often referred to as 650B (584 mm). Today, the 26-inch mountain bike is extinct - except among children. Because the advantages of the large wheels prevail - from hardtail to downhill bikes.

Not available for mountain bikes: 27.5 inches Plus Format

A few years ago, some manufacturers entered the market with bikes in 27.5 inches, which relied on so-called plus wheels, so the 27.5+ bikes were born. Behind this are wheels with a diameter of 27.5 inches, paired with wider tires around 2.8 to 3.0 inches, which should bring more traction and ride comfort. But the wheels with XXL tires have not caught on. Bikes with a 27.5+ rear wheel are often found on e-mountain bikes, while the plus format is hardly ever found on classic mountain bikes. Although the diameter of 27.5+ comes close to 29 inches due to the wider tires.

Here, the difference between the common MTB wheel sizes becomes visible: 27.5 inches on the left, the plus version 27.5+ in the middle and 29 inches on the right. The traditional size of 26 inches no longer plays a role in current bikes.

Which is better: 27.5 or 29 inch?

The last few years show a clear trend: 29-inch has prevailed on a broad front against 27.5-inch wheels *. Better rollover behavior, more traction and a lot of smoothness - 29-inch wheels * have established themselves across all mountain bike categories. Bikes in 27.5 inches are found much less frequently, predominantly in the enduro segment. However, there are also many manufacturers who rely on 27.5 inches, especially for small frame sizes.

Pro 29 inch: Advantages of large MTB wheels.

With obstacles such as stones or roots, the mountain biker faces regularly. With small wheels, the front wheel must be lifted even with medium-sized obstacles. Large wheels, on the other hand, simply roll over them. So the driver does not have to worry about it, but can fully concentrate on the trail. The good rollover ability of large wheels also increases the smoothness of the ride. The wheel remains quieter, even with many successive blows from the ground and at high speed downhill.

Pro 27.5 inch: Disadvantages of large MTB wheels.

The smooth running brings great advantages on rough passages, but is rather a hindrance in narrow, technical passages. By the large wheels increases namely the wheelbase and thus the effort of the pilot to move the rear wheel. The additional weight and the larger diameter increase the rotating mass. As a result, larger wheels react somewhat more sluggishly. This is particularly noticeable during acceleration. Due to the higher rotating masses, you need a little more power on a 29-inch bike when changing direction and the playfulness of the bike decreases. For small male and female riders, this disadvantage is even more serious. Many manufacturers respond with adapted wheel sizes. Thus, small frame sizes are often equipped with 27.5-inch wheels (size XS and S) and the larger frame sizes (mostly from M to XXL) with 29 inches.

Conclusion on the right wheel size on a mountain bike

29-inch wheels have established themselves in all mountain bike categories, because the advantages clearly outweigh the disadvantages. Only in the enduro segment and with small frame sizes are there still bikes with 27.5-inch wheels. Bikes with a MX design are relatively new. Here, a 29-inch front wheel is in the front of the bike and the rear end holds a smaller 27.5-inch rear wheel. The aim is to combine better rollover behavior at the front wheel with more agile handling at the rear. This concept is already familiar from motocross racing.