TIL #1 – The Skewer ‘Spring’

Quick Release Spring

A conical spring. Many bikes are equipped with up to four of these and serve a purpose, we promise. 

The springs that are found on many bike wheel systems, what are they? Do they serve any real purpose? If you are looking to grow your bike nerdiness and want to understand the true function of these small, yet practical parts to your bike, you’re in luck.  This may be one of the more detailed explanations of the ‘why’ these springs are part of your bike, the ‘why’ to leave them on, and most importantly, the ‘how’ to use them correctly.

History of the Skewer / Need for a Spring

First, let us embark on a brief history of the system they are categorized with belonging to: the quick release, or skewer, on a bicycle’s front and rear hubs.  In 1930, Tullio Campagnolo, yup the guy with the famous name in Italian bicycle componentry, invented the quick release.  You know the part on the bike that makes wheel changes and saddle height adjustments super easy, yes, that was invented nearly 90 years ago.  While the quick release was and is extremely beneficial in today’s cycling world, the addition of the ‘spring’ is its finishing touch.  Simply put, the springs that are found on either side of your hub, center the quick release, making wheel swaps all the easier.  By keeping the spacing equal between the hub locknut and the clamping face of the quick release, this small spring can allow for easy, one handed wheel replacement on a consistent basis.

The skewer, perfectly centered on the hub of this wheel, thanks in full part to two small cone-shaped springs.

Spring Design

The cone shape that is seen in this spring also serves a purpose, as the wheel is being clamped in place by the quick release, the cam action compresses the two ends of the skewer and in turn, everything between them.  This is the force that holds your wheel in place in the dropouts of both the fork and frame of your bike.  As the skewer essentially shrinks, the spring also compresses and the cone shape simply allows each level of the coil to sit next to each other under full compression.  Without the cone shape, the spring would just bind on itself and not allow for proper clamping of the skewer.  The cone shape spring has made wheel changes faster and kept wheels from falling off at 30mph, simple yet very effective.

Spring Placement / Orientation

The cone shape, as previously mentioned is meant to collapse on itself, but is there a proper orientation to installing it? Yes, and this is critical.  The big side faces out, small side in towards the hub.  The large diameter of the spring sits nicely in a cavity of the skewer’s clamping heads while the small diameter buts up against the axle of the hub.  When installed incorrectly, the large diameter of the spring rests over the axle, this has multiple potentials for disaster.  First, your fork and frame are designed to fit a determined axle, with a spring sitting over this axle, you have changed the effective diameter of the axle, producing an improper interface for your fork or frame, and hub.  When only one side is installed incorrectly the wheel is no longer perpendicular to the frame or fork, off by the thickness of the spring coil, this translates to more than the 1mm at the axle the further you get from the axle.  This can effect your disc brake, as the rotor is no longer at the same angle, effect the rim and brake caliper, as again, the wheel is no longer sitting flush with the frame or fork, and yup, effect your drivetrain.  Bicycles are precise machines, and when things are off, it can be felt throughout the bike.  The first thing our mechanics are checking when bikes come in for shifting or brake issues is this, are your springs installed correctly and is your wheel sitting flush in the dropout.  There is no simpler fix or easy thing to check if your bike is feeling off.

Spring installed INCORRECTLY.  Notice the spring sitting OVER the axle of the hub.

 

Spring installed CORRECTLY. Notice the properly exposed axle, making for a perfect junction with the frame or fork dropout.

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