Do Flexible Swingarms Damage Rear Shocks?

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We often see comments saying that flexible swing arms damage rear shocks. Let’s explore why that’s nonsense.

The steel construction of my swingarms, and the single pivot design, makes them more flexible under the loads acting on them. 

“But that will knacker you shock shaft!”, the ill-informed keyboard-warriors often cry…

Any engineer worth their salt will tell you that load tracks along the stiffest path. 

If you make the load path for lateral loads (sideways loads acting on the rear wheel) super stiff, the force will go that way.  Typically, the load is either taken by the chainstays or seatstays. 

A stiff mounting for the shock, such as a yoke or a swing link, means more load will track via the seat stays and then via the shock to the mainframe.  Make this load-path flexible and all the lateral load will track via the chainstays.  

There may be a lot of movement in the shock, but this does not equate to load.  As long as the shock can accommodate this movement, there will be no issues.  Spherical bearings do a good job of making the shock free from loading.  But the plastic top hat type shock bushes also do a pretty good job – the bushes do wear pretty quickly, but this is a £2 easily replaceable part, so no worries.

So some flexibility in the way the shock is fixed is a good thing.  This is counter-intuitive to many people, but it’s true. Speak to any suspension service centre and they will tell you about bikes with stiff yokes or linkages destroying shock shafts on a regular basis.

There's a school of thought that flexible swing-arms ruin rear shocks. Let's take a minute to discuss why that's nonsense.
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Joe Mcewan

Ex-aerospace engineer Joe Mcewan is the founder and chief engineer of Starling Cycles. Passionate, outspoken and fond of a cuppa and a debate, Joe loves to challenge the established thinking of the industry.

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