With this Quick Question series we will present fast fixes and collect comments from seasoned riders around specific D.I.Y. mountain bike repairs. While much of this trailside triage is covered in our repair articles and videos, this is a space for longtime riders and readers in the Singletracks community to share their knowledge. Please type your related experiences and advice in the comments below. Do you have a quick question? 🤔 Email [email protected]
While not every mountain biker wants to study the kinematic graphs of their bike’s suspension, there is a case for knowing what type of platform a given bike has. Maybe you want to learn a little about how your bike’s linkage works compared to another frame you’re considering, or you simply want to be able to speak accurately about the bike you own.
Our Quick Question this week is short and sweet, focusing on identifying suspension linkage. “How can I quickly figure out what suspension platform a bike has?”
In short, you’ll want to look at where the pivots and links are located.
First, let’s define a few things. A swingarm and chainstay are synonymous terms that reference the tube or lever between the main pivot and the axle or rear pivot. In the photo above, the black frame tube that extends from behind the chainring to its rearmost pivot just below the axle is the swingarm. The main pivot is the primary point that the swingarm lever rotates around. The clearest example of this can be seen on the Peacemaker pictured below. With dual-link designs, the main pivot moves slightly as the suspension compresses by using a second link or a moving device like an eccentric pivot or Yeti’s Switch Infinity system that slides the main pivot diagonally as the suspension eats impacts. Linkage refers to any lever that affects the system in addition to the swingarm.
If the rear triangle is a simple lever, hinging on one point and connected directly to the shock at another, the bike is a single pivot. Clear examples of this platform include any full suspension bike from Orange, or the Mullet Peacemeker pictured above. This design is loved for its simplicity and low maintenance, though that simplicity costs frame designers some limitations when it comes to anti-squat and anti-rise manipulation.
Linkage-driven single pivot platforms maintain their single pivot status because the swingarm or chainstay that extends between the rear axle and the main pivot ahead of it is one solid piece. These designs are sometimes rebranded “faux-bar” since the rear end can look like a four-bar design, though given its solid swingarm — it’s not. A quick way to identify a linkage-driven single pivot is by looking at the pivot closest to the axle. If that pivot is above the axle, on the seatstay, the bike is a linkage-driven single pivot. There will also be a secondary piece of linkage at or near the shock that engineers can use to manipulate the bike’s progression and other ride characteristics while adding stiffness to the system. Loads of bikes use this platform, including the Cotic Jeht, Cannondale Jekyll, Commencal Meta TR/AM, and the Kona Process X.
Some frames use flexing seat stays to achieve the movement of a single pivot while saving weight. The latest Specialized Stumpjumper is one such single pivot flexer, whereas its longer travel Stumpy EVO counterpart adds a link to the chainstay to create a Horst-link platform.
Another way to swing the single pivot is with a split-pivot, noted by the rear-most pivot’s location being shared with the axle. Like the linkage-driven platform, the swingarm is one solid piece. All bikes from Salsa, and both of the long travel options from Orbea are examples of a split-pivot in action. The video below shares some of the benefits of this platform.
Another common platform in MTB rear suspension is the Horst-link or four-bar design, created by its namesake, Horst Leitner. With the Horst system, the swingarm is interrupted by a pivot before it reaches the rear axle. The added link increases the number of places engineers can tune the bike’s performance out on the trail, including how pedaling and braking forces influence the suspension. Hoards of modern bikes use some version of the Horst-link, including the YT Jeffsy and Privateer 161 pictured above, the Specialized Enduro and Stumpjumper Evo, a GT Force, and a lot of long travel Rocky Mountain and Norco frames.
Flexing chainstays can also be used to create a Horst-link platform, like those on the modern Cannondale Scalpel. Like the flexing seatstays on the Stumpjumper, the carbon fiber chainstays are designed to mimic a pivot without the added weight of beaings and hardware.
The above platforms include numerous iterations and variations that all provide their own advantages and challenges. One other broad category for our general identification key is a dual-link or twin-link suspension design. These platforms use a pair of co- or counter-rotating links between the front and rear triangles to manipulate axle path and suspension kinematics. They can sometimes look like a single pivot, with the lower link tucked tightly behind the bike’s chainring as it is on the Santa Cruz Megatower above, but with a closer look, you’ll find that little second link. The non-driveside shot of the Pivot Firebird below shows both links clearly.
Dual link bikes are many and varied, including those from Giant, Ibis, Niner, Spot, and several others.
For a quick recap, if a bike has a solid swingarm, free of interruption from the main pivot to the rear axle, it’s some form of single pivot. If there is a pivot between the axle and the main pivot, it’s a Horst-link — a.k.a. four-bar design. Finally, if there is a pair of co- or counter-rotating links between the front and rear triangle, it’s some form of dual-link system. While there are several nuances and unique iterations within each of these, this is the quick and squishy of it.
What are some tricks you use to identify suspension design, or to determine important factors of a particular linkage?