Series A Downhill Race Frame

A simple concept came from the study of bicycle suspension designs and gave birth to the “Series A” downhill frame prototype.

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While this bike is only a prototype at this point, Function Bikes is interested in understanding the bike's potential as a product for sale.  If you have a couple of minutes to provide us with some feedback here: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it , we'd really appreciate it!  

Long story short, we'll be testing the Series A over a variety of conditions and in a number of events throughout the summer.  Watch the "news" section of the site for the latest updates.

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Engineering Principles behind the Series A:
As the saying goes,"Keep it Simple, Stupid!", so goes the engineering philosophy of the Series A.  The primary goals of the Series A design were to:
1. Balance “sprinting” type forces effectively through the swing arm angle. We noticed that out of the saddle, sharp pedal input causes unwanted bobbing even on bikes that have little or no movement under seated, constant cadence pedaling. If we can design a suspension which minimizes both, then we feel successful.
2. Realizing that the pivot must be relatively high to achieve this, we needed to solve the chain elongation issue. Routing the tension side of the chain over a pulley concentric or near the pivot is the best method to do this. Any standard chain guide can be used but it is clocked forward to minimize rear derailleur movement, but has no effect on the pedaling characteristics.
3. Maximize torsional stiffness of the frame for maximum control in rough, off camber cornering situations where more solid wheel control allows for a faster line. This is achieved primarily through a large diameter top tube which runs directly from the head tube to the pivot, but is also enhanced by the extremely wide pivot (check out the unique chain line through the swing arm) and extensive tube triangulation.

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More details:

-Why not aluminum?-
We believe that great bikes can be made from many different materials, but the characteristics of 4130 steel lend themselves well to our design goals and philosophy. With simplicity and function underlying our design goals, the steel structure lends itself well to a stiff, lightweight tube chassis in a single pivot, non linkage design.  Steel is also a great material because the fatigue life characteristics are far better than for aluminum, so you don’t need to worry about the frame cracking under long term abuse, the specific stiffness is far greater than aluminum, and the frame does not need to be heat treated after welding, which adds significant cost. Steel tubing forces us to be very strict in the design process which boils the design down to a no frills weight conscious frame with minimal machined parts to add weight.

-Why no linkages?-
Our suspension has a near linear rate because it is a single pivot design with no shock linkage. We believe that the performance benefits of a wheel to frame linkage or shock linkage have minimal benefit in this application, where easy maintenance, durability, and weight savings where possible trump an added linkage. Additionally, many riders have different preferences for the feel of the suspension and a linear rate provides a very neutral, predictable feel.

-Geometry?-
We have studied many racing frames very closely, and have done extensive testing to refine great handling geometry. Characterized by a low bottom bracket and slack head angle, every detail in the layout is set to maximize cornering control and speed in all situations. Our prototype geometry is being further refined and we will post the exact and full specs soon.

-Inspiration?-
We get really excited about the Orange 224, Balfa BB7, SWD Racing 218DH, and Morewood Izimu DH as bikes that share the same philosophy for what a downhill race bike should be as our Series A. Pure performance, simple, stiff, with great geometry and clean frame lines.

-Plans for Production?-
We plan to make these frames right here in Oregon, and offer them direct to consumers as a high quality dh race frame with no compromises, tons of performance, and great handling at a reasonable cost.

Series A at Sea Otter 2008:

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