Yeti Cycles

SB5.5 Carbon Mountain Bike Frame - 2016

You might think that, given its penchant for model names that are, essentially, serial numbers, Yeti Cycles' Super Bike family would be easily partitioned into specific sub-disciplines. The all-new SB5.5 Carbon Mountain Bike Frame would prove you wrong. If rear travel — the source of the numbering convention — is your chief criterion, then you might think the SB5.5 is an ambitious trail bike. But the short stays and 29in wheels tell a different story, one that features big watts on long climbs. And then there's the surprisingly compact wheelbase, which lends the SB5.5 a decidedly non-29er ability to dice techy terrain. So you could twist yourself into rhetorical contortions trying to classify it, or you could just let the bike speak for itself on the trail.

We've already seen Yeti impose its Super Bike philosophy on the wagon wheel category with the SB4.5, but the SB5.5's additional inch of rear travel rewards the more adventurous rider with a machine that flattens big hits with the same aggression that it cleans long climbs. By "more adventurous," we don't mean plodding bikepacking trips with 70lb of gear lashed about your person and frame. We mean aggressive. Not afraid to take the steppier line. Testing bikes on terrain they may or may not be able to handle. Instead of "more adventurous," some might write "reckless." Whatever. We'll leave those people with their overly restrictive, discipline-specific cycling while we take the SB5.5 across all the ups, downs, ins, and outs of true all-mountain riding.

Yeti's Switch Infinity suspension is the lynchpin of the SB5.5's seemingly limitless capabilities. Its linear travel hits the sweet spot of anti-squat to keep pedaling sharp across rocky climbs, and it also erases the momentary harshness that its predecessor, the Switch Link design, would display when pushed to the absolute limit. Go ahead and ride the shock open; it'll still claw up anything without sacrificing on big hits and deep rollovers.

The key difference between Switch Infinity and the Switch Link design it replaced is that the older model exhibits a momentary harshness when rapidly successive hits kept it hovering above the 30% stroke point. To address this, Switch Infinity replaces the Link's sinuous travel arc with a linear plane of motion, so the eccentric link changes direction without getting caught in the minute dead spot that produces that harshness. Of course, 95% of all riders won't ever push the Switch Link hard enough to experience this dead spot, but Yeti (being Yeti) went ahead and fixed it anyway.

Other than those two changes, veteran tribesmen will be relieved to learn that the suspension systems are fairly similar. Like the Switch Link, the Switch Infinity slider travels upward under the first phase of compression, when the SB5.5 is settling into its sag point. As the rear end compresses deeper, the direction changes, and the DH-inspired slider travels down toward the bottom bracket shell to maintain a steady pedaling platform. This change of direction is smoother, without the above-mentioned dead space, but the effect is the same. Deep in the stroke, it works in conjunction with the upper pivot to produce a vertical wheel path that flattens big hits. You'll be tempting faster, straighter lines across the chunky stuff, because the SB5.5 is just about the perfect trail buddy, effectively tidying up sloppy, questionable lines and sweeping rider errors under the rug.

The frame itself is actually built to Yeti’s Gravity spec, so it can handle everything from shuttle loops to lapping big lines in the bike park. Like the overly ambitious kid in the buffet line, we've got big eyes and even bigger appetites, but the lines we size up are often bigger than our bellies can handle. Fortunately, SB5.5's got an uncanny knack for smashing through questionable decisions. Again, this isn't just marketing palaver; the bike was built with feedback from the likes of Yeti's own Rude, so it has DH in its DNA.

Despite its gravity pedigree, the SB5.5 is remarkably similar to the SB4.5 on fast singletrack and climbs. When it comes to the fluid world of off-road bikes, the "best in class" label should only be applied with a delicate touch and a healthy dose of caveats, and that lofty qualifier should definitely never be applied while still basking in the smells-like-recess afterglow of your first experience on the machine in question. But we can't help it. The SB5.5 exhibits what may well be best-in-class pedaling, feeling more like the SB4.5. In addition to the high-modulus carbon lay-up (no alloy, no added weight, no shortcuts) and Switch Infinity suspension, we suspect that the Boost axle standard plays a role here. For starters, Boost is just stiffer. Wider bracing angles for the stays and the spokes make for less wag and more efficiency. That's bike physics 101. The wider spacing of Boost also let Yeti's engineers slam the rear wheel up, so the SB5.5 enjoys the same efficient, agile chainstay length as the 4.5.

Finally, the obligatory paragraph on compatibility and standards. The Boost rear axle wants to be mated to an appropriately Boosted front axle. Don't let it down. It also demands that you leave your granny gear aspirations at the door: the SB5.5 is for one-by setups only. The frame allows clearance for mid-sized tires, but going any bigger than 2.3in out the back might start testing the extra space allowed by the Boost spacing. The frame takes a 44/56mm head set and a PF92 bottom bracket, dimensions meant to stress stability and stiffness all around.