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Suspension cluster · Systems

Linkage single pivot and flex-stay

Quick answer

It's a single pivot with two tricks: the shock is driven by a rocker link (to shape the curve) and the rear pivot is replaced by the flexing of the carbon (flex-stay), saving weight and bearings. It is the dominant system in XC and down-country (Scott Spark, Specialized Epic 8, Cannondale Scalpel, Orbea Oiz). Note: kinematically the wheel still traces a single-pivot arc, it is not a true four-bar.

If your XC bike weighs next to nothing and "has no rear pivot", this is it. And brands sell it as a "four-bar", but it isn't — and here we explain why that matters.

A plastic ruler bends and springs back on its own. What if that controlled "bending" replaced a pivot with bearings? That's the flex-stay.

Flex-stay: single pivot with a rocker that drives the shock and a carbon seatstay that flexes instead of a rear pivot
The rocker shapes the curve; the carbon seatstay flexes in place of a pivot.

What it gains and what it gives up

For
Light (no rear bearings), low maintenance, stiff, curve shapeable with the rocker.
Against
The flex limits travel (ideal for XC, not enduro); the carbon must be well engineered against fatigue.
Used by
Scott Spark, Specialized Epic 8 / Epic Evo, Cannondale Scalpel, Orbea Oiz, Santa Cruz Blur.
Marketing error (corrected): many brands call it a "four-bar". It isn't. Without a real articulated pivot between the main pivot and the axle, the wheel path is that of a single pivot (arc), not that of a Horst Link. The flex simulates the joint only to spread stress, not to change the kinematics.

Frequently asked questions

Is it a four-bar?

No: without a real pivot near the axle, the wheel follows a single-pivot arc. Brands call it a "four-bar" but kinematically it isn't.

Why do XC bikes use it?

It removes bearings: saves ~150-200 g and maintenance. For short travel, the carbon flex is enough.

Is your XC bike a flex-stay?

Tell us the model and we'll tell you its behaviour and ideal setup. Message us on WhatsApp

Related

How suspension works → Single pivot → Horst Link / four-bar → Progression curve →

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BikeLab-pedia · Suspension cluster / Suspension kinematics explained / Carlos Eduardo Ravello Joo · BikeLab Studio · Trujillo, Peru