We are used to see linkages on full suspension frames. Why did we switch to a slider?
At the very beginning of full suspension frames in mountainbiking, linear sliding suspension elements were rather the norm than the exception. Famous examples are AMP Research's B2, Manitou's FS or Yeti's first ARC full suspension frames. All of them used the shock as a linear guide, which resulted in shock failures being a frequent occurence, so everyone moved over to linkage system. Now we slowly see slider systems coming back, why is that?
Generally speaking you want linkages to be stiff, light, and providing good suspension characteristics. Small linkages are light, stiff and help with packaging (aka putting bottles into usable positions on your frame). But unfortunately for good suspension characteristics you want rather long linkages. Linkages turn a linear motion into a rotations, which means trigonometric functions get involved when it comes to the suspension ratio (the ratio between travel at the rear axle and shock stroke). The more the linkage needs to rotate the more the suspension ratio curve looks like a sinus curve, but ideally we would want a straight line.
A slider is small, compact and stiff, but also represents an indefinitely long lever.
General consensus among suspension experts is that it is favourable if the suspension ratio steadily increases when going deeper into the travel available. By omitting rotating links we achieve a suspension ratio graph that is very close to that ideal straight line from top out to bottom out.
The comparison of the leverage ratio between the Essential and the Evolve shows how we achieve a much more linearly falling rate with the slider.
The slider suspension allows us to tune characteristics like anti squat and progression independently and in quite simple ways. For example, changing the angle of the rails just changes the progression, moving them up or down only increases or decreases travel, and moving the main pivot changes the level of anti squat.
Because the shock is only moving linearly, but not rotating around the eyelet, and there is no space needed for a linkage, we can nestle it tight below the top tube. This creates space for a second bottle on the seat tube and a low stand over height.
The slider is using the same components used in high end suspension: Norglide bushings slide on hard anodized, polished aluminum rods. Swiss-made low friction SKF seals keep the dirt out.
