In recent years the mountain bike industry has seen a variety of different wheel and tire sizes gain popularity – 29″, 27.5″, fat bikes, 27.5″ PLUS. As the dust settles, many have come to the conclusion that 27.5″ wheels are here to stay. They offer the best of both worlds between the traditional 26″ mountain bike wheel, and the oversized 29″ wheel.

Most Montague folding mountain bikes are equipped with 26″ wheels to maintain both off-road ability and a small folded size, but for those looking for the best performance possible come two new models. The Paratrooper Highline and Paratrooper Elite are the first folding mountain bikes to come standard with 27.5″ wheels. Let’s take a look at the advantages.

Rollover

The number one reason larger wheel sizes have become more common on mountain bikes is their ability to roll over obstacles. A larger wheel has a shallower angle of attack when approaching an obstacle. This makes for a smoother ride both descending and at slower speeds when climbing.

The above graphic allows you to visualize the difference in angle of attack. Based on a 4″ tall obstacle, a 27.5″ wheel has an angle of attack that is 4° shallower. This works out to rolling over the obstacle 9.8% more efficiently.

Rotational Inertia

A larger wheel also has more rotational inertia since most of its weight is farther from the hub. 27.5″ wheels hold their speed better so once you get moving, you stay moving.

Traction

A larger wheel also has a larger contact patch with the ground, and that means more traction. Wide tires and low tire pressures are used for the same reason, to increase the size of the contact patch. A larger diameter wheel naturally has a longer contact patch, which provides more rubber on the trail.

Go Even Larger?

You may be asking yourself, why not go with as large a wheel as possible?! There are disadvantages, which become even more pronounced as wheel size increases. After the 29″ wheel craze swept the mountain biking world, many riders settled on 27.5″ after trying all the options. The primary complaint with 29″ mountain bikes is that they don’t handle as well as their smaller wheel counterparts; that they aren’t as nimble. They tend to not react as quickly in corners which can be troublesome on narrow winding trails. Also, that same rotational inertia that helps maintain speed, also makes accelerating more difficult.

The general consensus is that 27.5″ wheels offer the best combination of larger wheel performance benefits with minimum drawbacks. If you think you want to try this wheel size, take a look at the Paratrooper Elite and Paratrooper Highline – 27.5″ hard tails that can still fold for the car trunk.