Motorcycle Shock Rebound Valve Stop Washers

Your rear shock absorber has a thick metal disc with machined passages flowing between both flat sides.

Stacked on both sides of this piston are the valving shims, a complex collection of thin steel washers that flex when pushed by oil pressure. When the coilover compresses, oil flexes the compression shims open & pushes through the piston holes to the other side, creating friction & heat. If the damper is pushed harder, it flexes further, allowing more fluid through. After a bump, the coil spring pushes the bike back to ride height so oil is squeezed back through the piston & rebound shims to the other side, absorbing more energy.

You don't want the shims flexing too far though - or there'd be very little resistance - so these thick stop washers help set a minimum damping level by limiting flex distance.

Your motorbike's internal valve shims come in a huge range of diameters & thicknesses, with the comp stack on one side & reb on the other, and are arranged in a very specific order to create the right damping characteristics. The piston and it's shim stacks are then attached to the end of the shock shaft using a locknut.

To make sure the suspension fluid can only flow through the correct holes, rubber o-rings and a teflon coated bush (or a soft PTFE band) seal around the outer diameter. We also sell complete shock pistons with the seals already installed.

It's all basic science but there are thousands of different variables that change the way it feels - our shim equivalence calculator can help - and that's why experienced tuners test and refine all that data on a suspension dyno. If you want to know more you can check out our suspension mods for your budget article to better understand how to approach tuning based on price vs performance, or watch Teknik's suspension guru Nick rebuild and revalve a shock.