GIANT 27.5: RIDE WITHOUT LIMITS.
The off-road world now has three wheel sizes from which to choose. Through extensive research and ride testing, Giant has
thoroughly analyzed how each size performs under different riding styles and in varying conditions. Our findings show that
mountain bikes with 27.5-inch wheels deliver superior performance without the compromises of 26 or 29-inch-wheel bikes.
So to create the best off-road riding experience, Giant has fully committed its 2014 lineup to this superior technology.
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: Three reasons to believe
Lighter Weight
• 27.5-inch wheels are only five 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.
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.
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.
1. Weight
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.
Roll-over
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.
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.
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3. Control
Frame Geometry
The larger the wheel, the more difficult it is to optimize geometry, especially on smaller frames. As the frame size decreases,
head tube 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.
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.
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