True Beauty Comes From Within

One of my most favorite people to converse with online is Keith Scott who is the design engineer for Banshee Bikes.  Keith is a wealth of knowledge and has helped me understand the design and mechanics that go into mountain bikes.  From time to time (when he finds time) he will be contributing articles to this site.

Today I asked Keith to explain Banshee Bike’s internal ribbing design for their seat and chainstays.  To my knowledge (and Keith’s) Banshee Bikes is the only bike manufacturer using an internal rib.  So what is it?

Internal ribbing makes the rear end of Banshee Bikes very laterally stiff meaning all your pedal power goes to the wheel rather than frame flex.  Frame flex is something that most riders overlook.  They think a lighter bike will always accelerate faster.  However, a heavier and stiffer bike is much more likely to beat a lighter one off the line.  Frame flex is probably equally as important as suspension design because it accounts for a lot of the efficiency when pedaling.

The process used to manufacture internal ribbing on bikes is cold form extrusion. Cold form extrusion is a process in which the material is drawn and pressed through a die which creates the shape by aligning the material.  The nice thing about extruded tubes is that the grain structure of the metal is all aligned in the process which makes the material stronger than it was before extrusion.  Similar to how forged parts are stronger than CNC machined parts for the same weight.

The rib not only increases the second moment of area and structural rigidity of the tubes, but it also makes the bikes much more quiet.  You’ve probably ridden a big hollow monocoque frame and have noticed the really loud and hollow sound made from chain lap or objects clashing agains the metal surface…with internal ribbing this noise is significantly reduced.  Not that noise when riding is really important…  Read more