Posted by: Brendan | September 15, 2010

Symphony Prototype- Full Suspension Siren

The first true Full Suspension Siren. Symphony proto #01

Symphony proto #01, a good start toward something that’s been on the collective Siren mind for a little while now. The criteria for this project are:

and, as an additional benefit; customizable.

In the world of high tech mountain bikes, there are two parties at work bringing us the better/faster/newer suspension designs that feel cushy over bumps and actually pedal decently up hills: bike makers and damper makers.

The bike makers who play in this game use their new, smart designs to innovate, patent, and offer something new & unique to the market. (that you’ll want to buy, right?) But the damper makers have done the same thing, especially in the last five years or so. The advances in lightweight, platform damped shocks and “anti bob” or “anti squat” technology are on par with the mechanical linkage offerings from the bike makers. We’ve ended up with some really smart suspension designs, so smart in fact you’ll often hear the bike makers proclaim their designs “work better with platform damping turned off.”

As a bike maker myself, I’ve approached our full suspension design from a different angle. Rather than coming up with a new linkage-type design that tiptoes around existing patents, we’re going with a tried and true, simple design while evolving the concept a bit further with our materials flexure concept originated on the Song.

The Symphony Suspension Design

The suspension design follows in the spirit of our softail, the Song, taking dissimilar materials flexure a step further, up to 3.5″ / 4″ of rear wheel travel on this bike. We used Finite Element Analysis to work up the basic shape of our flexure and equalize stresses throughout a 4″ suspension cycle.

Additionally, the main pivot placement is raised in relation to the bottom bracket shell for better pedaling efficiency. Pretty basic stuff in the mainstream of full suspension bike designs. We’ve added our proprietary torsion brace to the equation (again with a tweak from the Song design) to keep things as stiff as possible.

The secondary pivot is eliminated, again by use of materials flexure. In this case, we’re using thinwall titanium to handle this job, and matching the arc of the rear axle path closely to that of the top link assembly. You’ll notice the Symphony’s long top links, they’re as long as reasonably possible to work with the arc the seatstays make as they move through the suspension cycle. We will likely move to a bolted, or welded design to join the two links for added stiffness. Again nothing earth shattering.


I’ve been riding this prototype for about a month now. On the trail, the rear suspension feels firm under pedaling pressure, enough to get out of the saddle from time to time on fire road climbs. On the flats it feels smooth, comfortable. In and out of turns, I can feel the suspension load slightly at the apex of a corner. Feels good. The platform damped Manitou damper I’m using works as advertised.


The frame weight on this medium 29″ Symphony proto is 5.6 lbs with the aforementioned Manitou damper. As far as I know, this puts it in competitive range of the very lightest full suspension 29″ bikes out there. The full bike distinctly does not have that tank-like feel of so many FS 29’ers out there.

Simple (or K.I.S.S.)

The evolved use of materials flexure keeps things simple on the trail. Since the main pivot is comprised of our proprietary flex plate (200 year warranty) and proprietary torsion brace (ditto) this bike will never need a pivot bushing to be changed, lubed, beaten on, etc…

The Symphony proto here has a grand total of four sealed cartridge bearings, and zero bushings in the system… most importantly, none are in a main pivot or secondary pivot; they’re all in the top link. I may elect to use IGUS bearings in future Symphony for further reduced weight and simplicity. We’re designing this bike to be ridden in all conditions with minimal service time.


Because it’s a Siren, built here in the mountains of Southern California, we’ll be able to build the Symphony as a one-off. This will be a significant benefit to racer types, who might want the bike to fit a certain way, or tune the geometry of the bike… or maybe even tune the leverage ratio or rate to make the suspension feel a certain way. We can do it.


When can I buy one?
When it’s ready. We’ll be building and testing more varieties of the Symphony. Hope to have them coming spring 2011

How much does it cost?
The Symphony will be priced competitively with other high end, American made cross country full suspension bikes.

Is it awesome?



  1. IGUS please!

    IGUS + grease zerk fitting = riding in all conditions with minimal service time

  2. Nice, Brendan. Maybe I can take some pics and shoot some interview vid on the 25th.

    Innovation and customization keeps the little guys relevant.


  3. niiiiice! another bike on the bucket list!

  4. I like IGUS bearings too. Funny, though, if you ask them they’ll tell you to stay away from the zerk fittings/ grease injection, they say it’s not needed… but we know it works well in real world application.

    Grannygear, if you’re coming out on the 25th (of October) you’ll be two days late to the Enduro!

    PS- thanks for affirming my relevance. But I’m not really that small. I’m of average height… that’s what I remind myself every day, in front of the mirror… 😉

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