A day before Giant debuted its wheels in Mallorca, Spain, someone from the company told me that the new hoops would revolutionize bike wheels. The speaker and I get along well, so I probably said, “Baloney,” or even something stronger. Then, I asked that he tell me what was so special. He couldn’t reveal any details before the launch, and he didn’t temper his claim.
Now, it’s official. The Giant SLR 0 wheelset is out. They are on the new, top-end 2016 Giant TRC Advanced SL 0 (and Advanced SL 1 and Advanced Pro 0).and available to you to outfit your bike. The rims are composite, the rear hub’s internals use the star-ratchet system and they are tubeless compatible. Nothing revolutionary yet. But, according to Giant, your rear wheel is not balanced, especially if the spokes have a uniform pattern off the drive side of the hub. Sure, your wheel may be true, and the spokes may all have equal tension, but Giant says that’s not balanced when the rear wheel starts to spin.
The idea that forces on a bike are not balanced is nothing new. Many companies, Giant included, design asymmetric chainstays into their frames to manage the imbalance of forces on a frame caused by having the drivetrain on the right side of the bike. Of course, a rear wheel is dished: the spokes on the cassette side are shorter than on the non-cassette side to accommodate the cogs. But those spokes with a cross pattern—with some spokes leading from the threads (that is, where they attach at the rim) and some leading from their heads (that is, where they attach at the hub)—also have other forces acting on them. The ones that lead from the threads are pushing spokes. The ones that lead from the heads are pulling spokes. Giant says that if the wheel’s pushing and pulling spokes are set to the same tension when the wheel is at rest, then, once the wheel starts spinning, they won’t be balanced.
Giant’s solution to this revolving imbalance is called dynamic balanced lacing. When a rear Giant SLR 0 is laced and tensioned, the pushing and pulling spokes on the drive side (the non-drive side has a radial pattern) have different tensions. On the road, with the wheel spinning, the tension imbalance disappears. There’s also a difference in the leverage angles of pushing and pulling spokes. “If you look closely at the hub, you can see that a pushing spoke is a little bit closer to the hub shell and has a little bit less leverage. The pulling spoke has a little bit more leverage because it’s a bit farther in,” said Bill Miller, Giant global category manager for components. The spokes, therefore, have an improved transmission stiffness and can carry the force from the hub to the rims much more efficiently. This arrangement also makes the wheels more durable.
Another feature of how the spokes are arranged affects the wheel’s lateral stiffness, how much it moves from side to side. Good lateral stiffness makes a wheel track, and thus, corner better. As the spokes extend from the hub to the rim, they form a sort of triangle, with distance between the heads of the drive-side and non-drive-side spokes forming the base of the triangle at the hub. They all come to a “point” that the rim. A wider base makes for a more stable, stronger structure. But when 11-speed cassettes were introduced, that added cog made for less room. “When bikes went to 11-speed, it required a driver body that was 1.8 mm wider,” said Miller. “We were able to design a hub shell so we were able to anchor the spokes in such a way that we didn’t have to sacrifice the bracing angle. A lot of other companies had to increase their dish and therefore lose a lot of that lateral stiffness.” The hub flanges have actually moved out to improve the bracing angle, that base of the triangle, and to improve lateral stiffness.
Giant wanted to design a brake track that ensured you could stop well with these 30-mm-deep carbon-fibre rims. “We really wanted to create a wheel that could brake better than the competition,” said Jeff Schneider, Giant’s global gear marketing manager. “We’re using a high glass transition temperature, or high Tg, system. The rating is 245 C, but the industry standard is 160 C. What that does is that it allows the wheels to resist heat under a load longer. What the Tg rating means is that it is the point at which the resin goes from hard to soft, where you start to see the brake pulsate and the wheels can actually start to fall apart because the resin actually starts to melt.” Giant’s rating of 245 C means the rims will resist heat buildup from braking. The rating also means the new SLR brake pads that work with the wheels could be softer than most pads to provide better braking feel and modulation.
While Giant says it didn’t set out to build the lightest wheels, its data shows that it did. The Giant SLR 0, both front and rear, weigh 1,331 g. Giant weighed Specialized Roval Rapide CLX 40 at 1,372 g and the Zipp 202 Firecrest at 1,410 g.
The Giant SLR 0 wheelset is the top-of-the-line. In second place is the SLR 1 system. These wheels have the same rims as the SLR 0. The SLR 1 rear hub uses a pawl-driver system instead of the star ratchet. The spokes on the SLR 1 wheels are also Sapim Race and Sapim Laser instead of the DT Aerolite and DT Aerocomp on the SLR 0. Canadian prices aren’t yet available, but, south of the border, the SLR 0 will be US$2,300 and the SLR 1 will be US$1,300 g.
I rode the SLR 0 wheels as I tried the new Giant TCR Advanced SL 0 in the mountains of Mallorca. Their high stiffness and low weight meant I could climb efficiently on the twisty roads. When I had to mash on the pedals for a burst of speed here and there, the wheels always responded quickly. In the corners, I found the SLR 0 front and rear wheels tracked well together. Finally, and this feature was important to me while descending for kilometres on unfamiliar roads, the pads and rims worked very well to slow me down, even in a hurry. The weather in Mallorca in June, as you can imagine, was stunning: sunny and hot. Thus, I still need to see how those wheels stop in the rain. It’s a test I’m even looking forward to in the not-too-distant future.