Revolutionary. There is no other word to describe Yeti’s newest 6” travel trail/all-mountain bike dubbed the SB-66. The “Switch Technology” suspension that sets this Yeti apart from other bikes utilizes a unique eccentric pivot above the bottom bracket to build a bike that takes the best characteristics of two radically different suspension designs and combines them while eliminating their drawbacks.
The two types of suspension are rearward axle path designs and neutral pedaling suspension designs. Examples of the first type are rare and limited primarily to downhill bikes such as Canfield, Balfa, Nicolai, Honda, and nearly every gearbox bike ever made. Examples of neutral pedaling bikes include Specialized and Ellsworth.
Bikes with rearward axle paths have a chainstay length that increases as the suspension goes through its travel. This is desirable for a number of reasons. The first is that as pedaling places tension on the chain, it will pull the suspension down thereby resisting compression, resulting in better pedaling performance. The second is that as the front and rear suspension of a bike compress, so does the wheelbase. This is due to the head angle of the bike requiring the wheel to move backward toward the bottom of the head tube. At the same time the rear wheel moves backward, the suspension compresses keeping the wheelbase length more constant and keeping handling in high-G corners more predictable. Lastly, all things being equal, rearward axle paths react to bumps in the trail better than other suspension designs by moving away from the object that activated the suspension.
There are huge drawbacks to this design however. As the chainstay lengthens the rider has less leverage on the handlebar to loft the front wheel making it difficult to manual. Even worse however is that the further the suspension goes into its travel, the more tension is placed on the chain eventually causing pedal kickback. This is a jerk felt at the pedals that can be truly annoying on a steep rocky climb. The only way to combat this is to use an elevated drivetrain pulley to keep chain growth to a minimum. But these pulleys make it impossible to use a front derailleur and consequently double or triple cranksets. This is the reason why this type of suspension tends to be limited to the downhill world.
Neutral pedaling bikes are nearly the mirror image of rearward axle path suspension designs. In order to avoid pedal kickback the chainstay length shortens to avoid adding tension to the chain. Of course these bikes work great with double and triple cranksets and pedal well in nearly every gear. However, in order to accomplish this the rear wheel is forced to move forward when activated by a bump making it less responsive to the terrain and giving the bike a rougher ride.
The SB-66 takes the best of both designs. During the first third of the suspension travel the eccentric rotates the lower pivot rearward which in turn moves the wheel in the same direction to get out of the way of bumps. The rearward axle path also keeps the suspension firmer while pedaling.
Once the suspension reaches 100mm of travel, the eccentric rotates back to its original position, shortening the chainstay and thereby eliminating the possibility of pedal kickback. In this way Yeti’s Switch Technology emulates the neutral pedaling suspension designs.
But this is just the beginning of what makes the SB-66’s suspension special. Another improvement incorporated into it is a nearly flat suspension leverage curve. This means that the amount of leverage the rear wheel has over the shock stays essentially unchanged as it moves though the full range of travel. Flat leverage curves produce predictable suspension that matches the feel of suspension forks (which are always linear geometrically speaking) for a balanced ride that is easy to set up. It also allows for a wider range of working sag settings so you can get the geometry and feel of the bike just how you like it.
As if that were not enough, the SB-66 comes packed with a number of great features. These include splines on the bottom bracket shell to mount removable ISCG tabs. These tabs are available in either ISCG 03 or ISCG 05 to fit whatever chainguide you have. Then there is the Yeti chip system to convert the dropouts from 10x135mm to 12x142mm giving you nearly unlimited hub options.
Geometry wise, this bike follows the Yeti tradition of long top tubes, medium chainstay lengths, low bottom brackets and slack head angles. The SB-66 has a 67 degree head angle with a 150mm travel Fox 32 fork. This angle slackens out to just under 66 degrees when used with a 160mm travel Fox 36 fork. The tapered headtube uses inset style pressed in cups and is fully compatible with the Cane Creek Angleset if you prefer even slacker geometry.
The bottom bracket height ranges from 13.4 to 13.8 depending on which fork you choose. Either way, it is low enough to make the bike rail corners with confidence. Chainstay length is 17.1 for all sizes and top tube length for the SM, MD, LG, XL sized bikes are respectively; 23.1”, 24.1”, 25.1”, and 25.9”.
All of this adds up to a bike that will never hold you back. Yeti has all the bases covered with the SB-66. All that’s left is for you to get on the bike and enjoy the ride.
By: Daniel Slusser