Alutech Sennes FR 2015

El año pasado no existía ninguna horquilla de pletina simple con la que poder equipar a un cuadro de Mini-DH con ruedas de 27.5'' y por eso no se veía casi ningun modelo con mas de 160mm de recorrido, pero este año Fox ha presentado una versión de la 36 con 180mm de recorrido y los fabricantes están empezando a presentar algunos modelos de este tipo. En esta entrada voy a analizar a la nueva Alutech Sennes FR 2015, una versión de la Sennes DH que se adapta bastante bien para un uso tipo Bikepark-Freeride cambiando un par de detalles...

Como podéis ver en la tabla de excel y en las primeras gráficas el sistema tiene una Eficacia de Pedaleo bastante baja, al igual que pasaba con la versión de DH. El paso de un desarrollo de DH a uno de Enduro (38T Vs 32T) ayuda un poco, pero aun así el sistema sigue teniendo unos porcentajes de Anti-squat bastante bajos. El Pedal-kickback (13º) como es lógico se mantiene en un nivel muy bajo, mientras que el Brake-squat (93%) se mantiene en un nivel bastante alto.

En la gráfica del Leverage Ratio vemos como el sistema es Regresivo-Progresivo (2.8-2.9-2.15). El sistema va a funcionar bastante bien porque el primer tramo queda prácticamente por debajo de la zona de Sag y a partir de ahí el sistema es muy progresivo, pero si pudiese elegir preferiría que tuviese un LR continuo o un LR del tipo Progresivo-Lineal para poder adaptarlo un poco mejor a un amortiguador de aire. El Fox Float-X tiene además una medida bastante atípica (240x75mm), es la medida mas habitual para un modelo de DH y en un cuadro con 200mm de recorrido es una opción bastante lógica, pero aun asi sigue siendo una medida muy poco habitual.

Un saludo.

5 comentarios:

Unknown dijo...

Antonio, I have a question in connection to the regressive - progressive LR graph of this bike (or bikes similar to it). The bike does appear to have the disadvantage of the excessive suspension softness around SAG that you have drawn attention to before for bikes having this kind of LR graph (and shock linkage). Do, you think a shock with digressive or regressive (Penske's slightly different take on digressive design) damping can mitigate or eliminate this disadvantage? The question is kind of formal - it is only the shape and details of the forces and gradient graphs that concerns me. AS should be assumed to be 100% - that implies an unrealistically small chainring but as the damping forces of a fully open shock are what is important here that shouldn't matter.

Very generally, if I am seeing things correctly, a shock with digressive damping should have a somewhat steeper forces graph overall and a less sharply sloped post-SAG gradient curve. That could arguably go some way to fixing the softness around SAG arising from the lack of escalation in the LR curve at that point. And that seems compatible with undiminished suspension sensitivity to trail input i.e. the gentler gradient curve. I am not sure there are any dampers of this sort (besides the proprietary Fox dampers) out there yet, so obviously the question goes to the desirability and applicability of these dampers rather than their availability.

Un saludo
Chris

Unknown dijo...

Please take "proprietary Fox dampers" to mean Trek dampers manufactured by Fox in an exclusive partnership based on a Penske design.

Un saludo
Chris

Antonio Osuna dijo...

Main complaints with this type of LR are in fast corners, berms and G-Outs... All of them happens at very low shaft speeds, so it's impossible to fix the situation with LSC, you need a coil shock or an air shock with as much Mid-stroke support as possible.

Digressive Dampers are always welcome but they play a small role.

Best Regards,
Tony.

Unknown dijo...

My comment above was muddled. A digressive damper may have benefits for suspension function but not any literal impact on the forces or gradient graphs. Still, I think the choice of shock is not too good in this case. Something like the Vorsprung Corset air sleeve could help but currently these are only being manufactured for shorter shocks.

Un saludo
Chris

Antonio Osuna dijo...

Rock Shox does not make the Monarch Plus Debonair in that size either, so they are stuck with only a couple of options. They could get a coil, but it's hard to find a coil with platform damping, and they are a bit heavier...

Best regards,
Tony.

 

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