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Rear suspension bottoming out or bouncing

At the rear, the bike bottoms out over bumps (a sharp end-of-travel knock), bounces several times after a speed bump, sags too much two-up, or on the contrary stays hard as wood. The rear shock combines a spring (which carries the weight) and a hydraulic cartridge (which damps the oscillations). When the preload setting doesn't match your load, when the shock's oil is dead or leaking, when the spring has sagged after years, or when the swingarm and linkage bearings are seized, the rear end stops doing its job: degraded handling, a tyre that overheats, discomfort and accelerated wear. Many of these points can be adjusted or checked without heavy dismantling; a dead shock or worn bearings need parts but remain accessible. The key point: a rear suspension that no longer works is a genuine safety issue in corners and under braking.

Possible causes: rear suspension bottoming out or bouncing

These are the most common causes, from most to least likely. The guided diagnosis above helps you find yours, test by test.

  1. Preload / rebound wrongly set

    Basic

    Most shocks offer at least a spring preload adjustment (a stepped collar or a hydraulic knob) and sometimes a rebound adjustment (return speed). Too little preload bottoms out and sags the bike two-up; too much makes the rear hard and skittish. Wrongly set rebound gives a rear that bounces (too open) or stays packed down after a bump (too closed). It's the first, free reflex: set the preload for your load (solo, two-up, with luggage) aiming for the recommended static sag (about a third of the travel), and adjust the rebound. The manual gives the starting values.

  2. Leaking or dead shock absorber

    Intermediate

    Inside the shock, oil passes through valves to damp the movement. With age, the oil degrades or leaks past the seal (a greasy trace on the body or shaft), and the shock no longer damps anything: the bike bounces freely as if on a spring alone. Simple test: press hard on the seat and let go suddenly — a healthy shock returns once without bouncing; if it oscillates two or three times, the hydraulics are dead. On gas shocks, a loss of pressure gives the same result. A dead original shock is replaced (an aftermarket unit or a better-quality model); some high-end ones can be rebuilt.

  3. Seized swingarm / linkage bearings

    Intermediate

    The swingarm and the linkage system connecting the shock to the frame pivot on bearings or bushings that must stay greased and free. Without maintenance, water and mud make them rust and seize: the suspension becomes stiff, catches at the start of travel, creaks, and behaviour degrades especially at low speed. Check with the bike on a stand, rear wheel in the air: rock the swingarm sideways (play = worn bearings) and move it up and down (stiffness or a dead spot = seizure). Replacing or re-greasing the swingarm and linkage bearings is standard maintenance, a bit long but accessible with the right tools.

  4. Sagged spring (heavy / high-mileage bike)

    Intermediate

    On an old, very high-mileage or often-loaded bike, the main spring may have sagged and lost its rate: the bike sits too low, bottoms out easily and maximum preload is no longer enough to restore the right height. It's more common on big tourers and cruisers that carry a lot of weight. Confirm it by measuring the static sag: if it stays excessive even at full preload, the spring is tired. Solution: a new spring of the right rate, or a complete shock better matched to your weight and use.