How Does it Work?: The SILCA Presta Chuck and 242 Gasket

How Does it Work?: The SILCA Presta Chuck and 242 Gasket

We receive a lot of questions about our chuck and how it operates.  Over the last 30 years, the market has become flooded with pump and chuck designs of various complexity and part count, some with levers that flip up, some flip down, others like our own 'Hiro' Side Lever chuck work unlike any other, and yet the classic SILCA Presta Chuck continues to remain a classic, a favorite of both bike shop and pro mechanic alike for it's simplicity and ultimate durability.  In 

In the early days of the pneumatic tire, all pumps had hoses that threaded onto valves.  Early silca pumps were no different, with even the Impero frame pumps of the 1920's and 30's having a hose that threaded onto the valve stem.  This is a robust design, but time consuming and occasionally frustrating for both the home and professional mechanic alike!

In the 1940's SILCA developed the first variation on what we now sell as the 17-4 Stainless Presta Chuck.  This design tapped into lessons from one of the most iconic designs of all time for inspiration: The 2000+ year old Roman Arch!

Roman Arches used in the Construction of a 2000 Roman Viaduct

The idea is quite simple: Make the top of the gasket a dome or arch shape and allow the valve stem to serve as the 'keystone'.  As pressure rises on top of the gasket, it transfers the load into compression on the valve stem gradually increasing holding force as pressure rises!  

All loads on the arch are converted to compressive forces on the Keystone and the Springers

For the new SILCA we have updated this classic with modern materials and the benefit of Computer Aided Design and modeling.  The new SILCA Presta chuck replaces the classic brass with 17-4 Stainless Steel, a magnetic stainless originally designed for aircraft landing gear and revered for it's strength, corrosion resistance and  beauty, but more importantly, replaces the classic natural latex rubber gasket with an exceptionally high performance Synthetic Elastomer originally developed for use in the harsh environments experienced in oil drilling and sub-surface mining.  We have further improved upon this classic design by using a Parabolic Geometry on the top gasket surface.  This geometry allows us to carefully tune the holding power of the chuck to the pressure in the line.  Your gasket will always hold the valve stem with 25-30% more force than required for a given pressure, this ensures that it won't blow off while inflating, yet is easy to remove when you are finished!

Parabolic Elastomer converts Line Pressure into Holding Power

 These technologies are used in the SuperPista Ultimate, 17-4 Stainless Chuck and 242 Gasket  


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