2015 giant anthem sx 27.5 Mountain Bike Review from Pedal Power in Richmond VA

 

The lightweight frame and 120mm Travel Fork create amazing performance

Giant didn't create the 27.5 category, but they saw the future and have been leading the industry. Nowhere is that as noticeable as in the new Anthems. Check out these amazing specs:

• ALUXX SL-grade aluminum frame with 4 inches of smooth Maestro suspension
• 120mm-travel Fox Float CTD Performance fork with 15mm thru-axle
• Fox Float CTD Performance rear shock
• Giant P-XC2 rims, Giant Performance Tracker hubs, stainless butted spokes
• Shimano SLX / XT 10-speed drivetrain with Shimano SLX hydraulic disc brakes

Listen to what the reviewers are saying

From the theBerm.com.au:

What is an Anthem SX?

For 2015 Giant have created two ‘trail’ versions of their Anthem XC race bike and called it the Anthem SX. For those of you unfamiliar with Giant’s Anthem, it’s a 100mm travel full-suspension XC race bike. To create the Anthem SX, Giant took a standard Anthem frame for 27.5” wheels and bolted on a 120mm fork, a remote adjustable seatpost, and a shorter stem – with brilliant results. There’s an aluminium version with a 2X (two chainrings) Shimano drivetrain and Fox suspension that retails for $2999AUD, and the version reviewed here, the $4999 Advanced version that has a 1X SRAM drivetrain and RockShox suspension.

 See his very in depth reporting on the Carbon version here. 

Why 27.5?  Giant was ahead on this. They jumped in when the realized the following:

Lighter weight

Significantly lower bike and rotational wheel weight helps you climb faster with less effort.

Overall BikeWeight

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

Weight Comparison

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

2. More efficient

Snappier acceleration and a reduced angle of attack for a smoother, more agile ride.

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

A larger tire contact patch, increased stiffness, and optimized frame geometry improve traction, braking and handling.

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, 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.