QUELLE — Website GIANT — Bericht von 2013 —

Why 27.5?

There is a common misconception that the performance of 27.5 technology sits squarely in the middle between 26 and 29. But as our data reveals, 27.5 actually displays some of the best characteristics of 26 and 29—and it never measures out exactly in the middle.

When it comes to weight, 27.5 performs more like 26—it’s light and agile. And for efficiency and control, it outperforms 29. Rather than introduce a single 27.5 model, as some of our competitors have, Giant is rolling out entirely new designs and engineering solutions to maximize the performance advantages of 27.5-inch wheels. Here’s why:

27.5 Technology: 3 Reasons to Believe

1. Lighter Weight

  • 27.5-inch wheels are only 5 percent heavier than 26-inch. By comparison, 29-inch wheels are 11 percent heavier than 26-inch.
  • Overall weights of 27.5 bikes also trend closer to 26 than heavier 29 versions of the same series

Every rider experiences two types of weight affecting their ride: overall bike weight and rotational wheel weight. Here’s a closer look at these two forces and how different wheel sizes alter the dynamics of your ride:

Overall Bike Weight
Compare the weights of identically equipped bikes with different wheel sizes and you’ll see substantial weight differences. As expected, the 26-inch-wheel bike is somewhat lighter than the 27.5, and substantially lighter than the 29 (up to two pounds of overall bike weight savings from 29 to 27.5). Every gram saved helps you ride faster.

Wheel/Tire Weight
The overall weight of a 27.5 wheelset (wheel, tire and inner tube) is only 5% greater than that of an identically built 26-inch wheelset. Compare this to the 12% increase of a 29-inch wheelset and you can see how a seemingly small increase in diameter results in substantial weight gain—and poorer performance when climbing or accelerating.

Static Wheel Weight
Lighter wheels/tires result in quicker acceleration and lighter overall bike weight—a win-win combination.

2. More Efficient

  • 27.5 wheels accelerate much like 26, outperforming the more sluggish feel of 29-inch wheels.
  • 27.5 wheels roll over obstacles with much more control than 26. That translates into more efficient cornering, acceleration and braking capabilities.

Rollover
Increased wheel diameter decreases the angle of attack (the angle in which a round object intersects a square object). This is a good thing. A 29-inch wheel rolls over a 6-centimeter square-edge obstacle 14% more efficiently than a 26-inch wheel does. In comparison, a 27.5-inch wheel rolls over the same obstacle 9.8% more efficiently than a 26-inch wheel does. Another way to analyze angle of attack is the degree of impact—where 26-inch equals X degree, 27.5 equals X-4 degrees and 29 equals X-6 degrees. Again, a shallower angle is better—so 29-inch takes the win, with 27.5 exhibiting nearly the same performance but without the weight penalty.

Acceleration
Arguably the most important benefit of 27.5 over 29 is quicker acceleration. This is the “snap” that a rider feels when they push hard on the pedals. It is affected not just by overall static weight but also where the weight is distributed throughout the wheel. The farther the weight is from the center of the hub, the slower the acceleration. So a similarly constructed 1000-gram 29-inch wheel is slower to accelerate than a 1000-gram 26-inch wheel—because the larger diameter rim and longer spokes place weight farther from the hub. The key to snappy acceleration is minimizing the weight of the outermost components (rim, nipples, spokes, tire, tube). As you can see, a 27.5-inch wheel is only 1.5% slower to accelerate than a similarly constructed 26-inch wheel, but a 29-inch wheel is 3.6% slower than a similarly constructed 26-inch wheel.

3. Better Control

  • The larger the diameter of a wheel, the greater the contact patch of the tire. A larger contact patch results in better traction—which improves acceleration, deceleration and cornering. 27.5 wheels provide a contact patch that is similar to 29-inch wheels.
  • The larger the wheel, the larger the frame dimensions must be—and that leads to unwanted flex. A flexing frame causes sloppy handling and slower acceleration under heavy power. A 27.5 frame flexes less than a 29 frame, resulting in better control.

Traction
The larger the diameter of a wheel, the greater the contact patch of the tire. A larger contact patch results in better traction, which leads to improved acceleration, deceleration and cornering. As you can see below, a 27.5-inch wheel has a similar contact patch to the 29.

Frame Stiffness
Lateral (side-to-side) frame stiffness can be affected by wheel size. To accommodate larger wheels, frame dimensions must be elongated. Therefore, a size medium 29-inch wheel frame has more lateral flex (bottom bracket and headtube) than a size medium 27.5- or 26-inch wheel frameset. Additional flex compromises handling under heavy pedaling or sharp cornering.

Frame Geometry
The larger the wheel, the more difficult it is to optimize geometry, especially on smaller frames. As the frame size decreases, headtube heights become higher (in relation to saddle height). On 26 or 27.5-inch frames, it’s less of a problem, but geometry limitations can affect smaller 29-inch-wheel frames.

Continue reading for more information, specs, pricing and full photo gallery of the new 2014 Giant and Liv/giant 27.5 models.

QUELLE — Website GIANT —