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Purpose of rear suspension linkage

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The first time i realised that there was this linkage system on my bike, i was scratching my head asking why they don't simply attach the shock on the swingarm..   Any anwser for me?

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Because our rear suspension reacts better for you the rider,with a rising rate.

Many have tried to replicate it with just a shock on to the swingarm but it is more difficult than just adding linkage.

The KTM version is good but in practice much more one dimensional than the equivalent bike with linkage. Eg you can set both linkage and non linkage suspension up to be great in "X" conditions and probably won't even notice the difference. Move just Abit away from " X" and the performance of the non linkage will start to drop off faster. Go even farther away from "X" and the non linkage will get all confused while the linkage still performs reasonably well.

This is just my real life experience.

Since I ride in variety of stuff on any given ride the linkage has a distinct advantage.

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Linkage allows for a sufficiently progressive action of the rear suspension to have compliance and traction over rough terrain with excellent bottoming resistance. 

KTM's PDS has the shock laid down at an angle in an attempt to mimic the rising rate nature of a linkage system.  Inside the shock they use two pistons and a tapered needle to attempt to kick in additional damping toward the end of the stroke.

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The PDS gives an increase of around 17% of rising rate where a linkage is double that ,the PDS has 2 pistons so later in the stroke the 2nd piston increases damping ( but not spring rate )

 

 

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Great explanations guys,

guessing all PDS setups typically use progressive rate shock springs as well?

Any pro/cons about those?

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I was pretty happy with mine (06 SX250) after a bit of mucking around with a progressive spring and different needle and valving.

Mine didn't come stock with a progressive spring, I think only the earlier ones did. (Mog?)

The setup was interesting really, and if done a little different when they designed it I believe could have been very tuneable. Being able to tune the suspension for different positions as well as speeds seemed like a good idea.

 

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The early progressive springs were too beefy and the rebound struggled to cope ,then they went to a mild progressive spring and that worked ,I think they still use them ,I liked the straight rate on the early PDS ,mainly because the progressive allowed it to sink too much at the beginning

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Anyone have good linkage data from the modern 4 strokes?  Curious about a few of them.

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I think only the KTM is radically different,the others mostly similar to each other ,I don't have the data

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