Mountain bikes have seen serious technological advancements in just a few short years—from dramatic improvements in suspension performance to new drivetrain options and, most recently, the growth (literally) of wheel, rim and tire sizes. It wasn’t long ago that riders were forced to ride 26-inch wheels, because it was the only option—unless you were an early adopter of 29er wheels. Well, a new crop of options have popped up in the form of plus-sized bikes, which promise the big traction and plushness of fat bikes without many of the weight and clearance drawbacks the early big-tire bikes were saddled with. Trouble is, many people don’t know what a plus-sized bike even is, let alone why they should be riding one.
The most recent debate in tire and wheel sizing is 27.5 versus 27.5 plus. With both wheels measuring 27.5 inches and offering a slightly different-sized tire, many riders wonder what the differences really are. To put it numerically, a standard 27.5-inch tire has a width between 2.0 and 2.5 inches, while its plus-sized brother has a tire that ranges from 2.8 to 3.0 inches. With less than an inch separating these tires, they can’t be that much different, right?
Wrong. Not only do plus-size tires require wider rims, they also measure very close to the diameter of a 29-inch tire—and it doesn’t stop there. Because of clearance issues caused by these bigger tires, bike companies are forced to create frames with wider rear triangles and forks with 110-millimeter front axles. The geometries of 27.5-inch- plus bikes are actually more closely related to 29-inch bikes. Looking into the Specialized Stumpjumper and Scott Genius lines, we can see that their plus-sized bikes share the same rear travel and have chainstay lengths similar to their 29-inch cousins. Since a 27.5-inch-plus tire has a diameter similar to that of a 29-inch wheel, it almost seems unfair to compare a standard 27.5 to its plus-sized version. In our minds, the plus-sized 27.5-inch tire is in a category all its own.
WHY CHOOSE A 27.5-PLUS BIKE?
Plus-sized bikes are still relatively new, and many bike companies have different ideas about what a plus-sized bike should be used for. Some companies design them for beginners who want to feel more comfortable on loose dirt. Other companies believe wider tires are the answer to shaving seconds off descents. In our experience with plus-sized bikes, almost every rider who hops aboard one is surprised by what the bike can do. The pros of a plus-sized tire start with greatly improved traction. Say goodbye to unwanted tire spin on steep climbs, because these puppies like to bite hard into the dirt. Cornering is also made easier by giving riders more confidence on loose or off-camber sections where a standard-sized tire might want to slide out. The other huge benefit is that the larger air-volume tires allow for super-low tire pressures. These low pressures equate to excellent small-bump compliance out on the trails. With these tires on a full-suspension bike, the trails feel like puffy clouds. There is really no doubt that plus- sized tires offer some clear advantages, but don’t get rid of your standard-sized wheels yet.
THE CONS OF 27.5 PLUS
Along with the benefits of plus-sized tires, there are a few cons. First of all, the choice of tires is fairly limited right now, and current options can be heavier than standard-sized tires. The new Maxxis Chronicle 27.5×3.0 tires will set you back $95 each, and the WTB Trail Boss 3.0 tires sell for $68 each. The Chronicles weigh 990 grams each, while the Trail Boss tires weigh 1125 grams. In our experience with plus-sized bikes, we notice the increased weight on just about every climb, which can be a real bummer.
THE VERDICT ON 27.5 VS. 27.5 PLUS
When comparing 27.5-inch tires to 27.5- plus tires, there is no clear winner. Both wheel options have unique characteristics that appeal to different riders. Standard- sized 27.5-inch bikes have more travel, shorter chainstays and lighter-weight tires, which all contribute to a fast and nimble bike. The 27.5 plus, however, offers more traction, the option to run lower tire pressures, and a tire diameter similar to that of a 29-inch wheel. The 27.5-plus tire rolls over obstacles better and grabs tons of traction, even when the trail is loose and dry. We aren’t likely to see 27.5-plus tires in cross-country events due to their weight, but they could become popular for enduro. Heavier tires don’t penalize enduro racers, because enduro racing requires riders to make up as much time as possible on the descents and corners rather than the climbs.
The bottom line is that plus-sized bikes have advantages and disadvantages, but whether or not a 27.5-plus bike is right for you is a question only you can answer after tossing a leg over one and giving it a go.
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