Yeti Unleashes A Radical Trail Bike: The SB-66

In early March a Yeti employee—not so subtly—mentioned the company had a new bike in the works. Only he couldn’t spill the beans. “Wait till Sea Otter,” he said. A couple weeks later, at the Taipei bicycle show, a Fox Shox insider told me that they were finalizing shock tune on an “amazing” new bike from Yeti. He couldn’t mention any details either. “Just wait,” he said, “you’re going to be astounded.”

Finally, at Sea Otter, Yeti lifted the veil on its latest trail bike, the SB-66. SB is short for “Super Bike,” the nickname bestowed on it by one of Yeti’s test riders. The first 6 is for the wheel size, 26, the second ‘6’ denotes its 6 inches (151.5mm) of travel.

But this is no ordinary Yeti. The SB66 uses an entirely new suspension platform designed by Dave Earle—a contract designer and former Santa Cruz employee who Yeti hired to work specifically on this design, called Switch Suspension Technology. Completely unique, the system uses an eccentric lower pivot to manage chain forces. This means the bike pedals incredibly efficiently, and the suspension works smoothly without being compromised by chain growth or rider input. Before we dive into the nitty-gritty details, here’s something else you should know about the SB66: It’s one of the best trail bikes we’ve ever ridden.

Switch Suspension Technology

By far, the standout feature is the dual-link suspension design with an eccentric lower pivot. As the suspension compresses, the eccentric, when viewed from the drive side of the frame, initially rotates counter-clockwise. Then, comes the twist: a bit more than halfway through the travel, it reverses direction and rotates clockwise.

A note about the language to follow: Yeti eschews the instant center/anti-squat methodology—popularized by Dave Weagle—of analyzing suspension because, Yeti says, it doesn’t take into account all the variables involved with a rider on a bicycle.

In Yeti’s view, proper control of chainstay lengthening counteracts chain forces generated by pedaling (and, in the later stages of the travel, by just the rider’s weight) which are trying to shorten the stays (creating squat, or bob). However, too much chainstay lengthening, however, can make the bike less sensitive when pedaling and the rider feels feedback in the pedals.

The Switch system lets Yeti make more rapid changes to the rate of chainstay lengthening than any other suspension design. This, they say, is the key to having great pedaling characteristics with no perceptible feedback, particularly later in the travel.

A Smooth, Supple Shock

Rate of chainstay lengthening is only one component of suspension performance. Another very important component is squishing the shock. Yeti went with a flat-ish ratio for the bulk of the travel because, as one employee told me, “It’s very easy to tune the shock, both air and coil shocks work well, it has a supported mid-stroke and predictable smooth travel feel throughout the travel. Also, adjustments to the shock via clickers have a larger effect. The adjustments are not "overcome" by the leverage ratio, which makes the suspension easy to tune for both air and coil-spring shocks.”

A slight increase at the end of the shock stroke helps overcome a forward hook in wheelpath. The forward hook, “is not optimum for bump absorption,” says Yeti, so a little increase in the leverage ratio keeps the suspension feeling plush. Yeti also says, “Since the rate of chainstay lengthening drops off at the end, you have less chain force "restraining” the swingarm and preventing it from wanting to move. This acts similarly to the slight raise in leverage, both helping you use all of the travel.” This is particularly helpful when using an air shock, which is progressive by nature.

An Aggressive Frame

Yeti will offer two versions of the SB-66: an aluminum version (seven pounds, with shock) and a carbon version (six pounds, with shock). The carbon version will come out in late 2011, but the aluminum version ships very shortly—like, this week. Frame features are similar between them; just material and frame weight (and perhaps frame stiffness) will vary. It should also be noted that this is only the first Switch Suspension bike from Yeti. More models will follow.

The distance between the upper and lower links is very short, for a compact system and a clean, low-slung look and lots of stand-over height. Yeti uses big thru-axles to connect the rear triangle to the links: a 15mm pin goes through the lower (eccentric) link and a 17mm pin goes through the upper link. The upper link’s lower pivot also uses a 17mm pin. The eccentric rotates on very large bearings and is fully sealed, according to Yeti. A nice touch is the chain slap guards molded specifically for the SB’s rear triangle.

The SB-66 uses some of the most progressive trail-bike geometry in the industry. The chart below has the details, but take note of the long top tubes—designed with a stumpy stem in mind. The head tube angle (with a 150mm Fox 32 fork) is similar to those often found on 165mm-travel all-mountain bikes; and the BB is lower than on many 140mm bikes.

Other details and features include:

• Tapered head tube with, in a change for Yeti, inset bearings

• High direct-mount front derailleur

• Full-length cable housing; rear derailleur housing internally routed through swingarm; remote dropper post guides

• Post-mount rear disc tabs

• Yeti’s rear axle chip system: accepts 9x135mm QR or 12x142mm thru axle

• ISCG ’05 tabs. • Fully compliant with a Fox 36 fork and coil-over shock. Some Yeti insiders use the SB with this setup for less-technical DH courses

Riding the Super Bike

I’ve had the opportunity to ride a pre-production SB-66 since April on my home trails. It’s an excellent bike—perhaps superb. It feels like a combination of two of my favorite bikes, the Santa Cruz Blur LT2 and Specialized Enduro.

The SB-66 pedaled great, better than any other Yeti by far. It might be more efficient while pedaling than the LT2 and it has a touch more rear wheel bite, especially when the rider is pedaling out of the saddle. And like the Enduro, the suspension felt sensitive, and unobtrusive.

Like the 575, the SB loved to be ridden hard and came to life at speed. However, the SB pushed through square-edged bumps better than the 575, so it was a little easier to ride in slow-speed technical terrain. The suspension held well in hard corners, limiting the sinking wallow that can upset a bike’s balance mid-corner. I had no trouble using all the SB’s travel, but I only felt the suspension bottom once, on an awkward flat landing off a decent-sized jump.

The SB’s geometry made it feel like a cross-country bike for professional downhillers. There’s a touch of the heaviness in the handlebars—common with low and slack bikes—but that only increased its high-speed stability. The bike absolutely flew down wide-open descents. Surprising then, it also performed admirably on slow-speed technical stretches of trail that demanded pedal-ratchets, 90-degree corners and trials like power moves. The SB’s firm suspension prevents bog and the shortish stays keeps the front end light enough to loft easily.

The SB whistled up climbs, aided by the firmer suspension and efficient pedaling. On occasion, the SB encouraged out-of-the-saddle climbing where a more XC-oriented trail bike might encourage in-the-saddle spinning, but, on the whole, it’s a very good climber. While I’m a fan of the low-slung geometry, it could present a challenge for some riders. The bike’s bottom bracket sits just 13.3 inches off the ground and could lead to whack-a-licous pedal strikes in rock gardens.

The SB-66 frame is very stiff and my prototype has been very quiet. Just keep in mind that there are eight bearings and three pivot axles to look after.

There’s no question the trail bike landscape is crowded and filled with a variety of stunning bikes. But, the SB-66 enters as a standout with unique suspension and progressive geometry. It’s not the trail bike for everyone, but if you want a bike that’s snappier than an all-mountain bike, descends like a DH bike, and can still “do it all,” here is your Super Bike.