At low speeds the oil bends the weakest shim and leaks through a bit, gently controlling the movement. They use a stack of different size shims to control oil flow within a cartridge. This is a Showa Separate Function Fork from a KX250 motocrosser, with one side housing the spring and preload, while the other houses the damper. You can only alter spring rate by changing the springs. Preload doesn’t alter the spring rate though - it just changes where the fork action takes place – you use it to adjust your ride height. Preloaded, they should drop about a quarter of the stroke if you’ve got your sag set correctly. Without it, you’d push the bike off its centrestand and the forks would sink down way too far, using up loads of the suspension stroke.
SHORT FORK FOLLOWER ROD FULL
And that’s just the start – both scenarios mean the forks aren’t working over their full stroke, so the damping doesn’t have a chance to work properly either.Īs the name suggests, it’s how much load is on the spring when the forks are fully extended. Conversely, if the springs are too hard, you’ll probably notice your wrists being pummelled over harsh bumps and the front tyre skipping over small ones. Well if your springs are too soft for your weight or riding style, you might find the bike dives dramatically on the brakes or bottoms out (ie the springs compress so much that the coils hit each other and there’s no spring effect to be had). As the spring compresses, the most densely packed windings eventually come together into a solid lump, effectively increasing the spring rate.
Progressive springs use variations in the windings to create the effect of multiple springs. So you might have a main spring that does most of the work, but when the forks compress a certain amount, they hit another shorter spring that joins in as well, making the forks stiffen up. So a spring rate of 10N/mm means it takes 10N of force to compress the spring by 1mm. By changing the diameter of the wire and the number of turns you can alter the spring rate, which describes how much force is need to deflect the spring a given amount. The simplest and most common is as you’d imagine - a single regular steel coil. There’s a spring in each fork tube to support the weight of the bike and allow the wheel to react to bumps, and a damping system to stop the bike bobbing up and down like a cork on stormy sea. Partly because, in principle at least, they’re simple. The new Gold Wing, numerous BMWs and a few rare groove bikes such as the Bimota Tesi don’t use telescopic forks, but it’s telling that everything else does, from loony motocross race bikes to Harley cruisers. The sealed damper cartridge is below the spring
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