[EN]What is that? How does it work?
Rock Shox has released the upgrade for the Debonair C1 2021 air spring with the intention of solving the problems of the previous version, the B1, i.e. the loss of almost 10mm of travel and the excessive sinking in the first part of the stroke, bringing the piston higher thanks to a taller seal head, and a longer foot nut which compensates for the total length of the rod, bringing the travel back to its nominal value.
This problem was fixed but the negative chamber became smaller, causing a reduction in sensitivity in the first stroke and support half.
So with the C1 update the fork actually works higher, but on bumpy descents you get tired more and sooner, due to greater difficulty in absorbing in the first part of the travel.
EverFlow offers an improvement over both versions of Rock Shox, making the most of the space to obtain a greater negative volume thanks to the TANK kit, that is a spring that replaces the topout bumper and a tank placed at the end of the shaft. In fact, in the Debonair system also the internal volume of the rod is part of the negative chamber thanks to the openings placed under the piston.
For those wishing to go even further, there is the MVP, (More Volume Please!) That is a modified seal head where the excess material has been removed, to further increase the volumes, and the wiper is also removed to improve the smoothness.
Advantages compared to version B1 2018-20:
-The fork works "higher" while maintaining a more open steering angle during the descent, giving greater confidence in the technically more demanding sections
- Larger negative chamber for better sensitivity to small and medium bumps
-More mid stroke support and progressivity
Advantages over version C1 2021:
-Much larger negative chamber, the sensitivity increases consistently, but always remaining "high" in the travel.
-More mid stroke support and progressivity
-Feeling similar to that of a spring fork in the first half of the stroke
-Excellent price / performance ratio
-Great excuse to get a service
-The greater progressiveness may make it more difficult for some light riders (<70kg) and with long travel fork (> = 170mm) to use the full travel
What about the Zeb?
The Zeb has a pneumatic spring very similar to the C1 of the "cousins" with 35mm stanchions. It has a removable piston (on the right) with a small hole that makes the internal volume of the rod communicate with the external volume; unfortunately, however, it is almost always misaligned with respect to the two holes in the shaft. This creates an obstacle that compromises the optimal functioning of the fork.
For this reason, in the dedicated kit, in addition to the Tank there is a revised piston to always keep the equalization holes of the shaft free, and thanks to its special design it frees up volume in favor of increasing the negative chamber.
The importance of the negative chamber
The dotted line indicates the space reserved for the negative chamber, delimited at the top by the piston x ring, and at the bottom by the seal head o-ring, to which the internal volume of the rod must be added. The vertical position of the piston is determined by the dimple height, a small recess inside the stanchion that allows the two chambers to communicate. When the fork is "at rest", the positive and negative chambers have the same pressure. The fork, by compressing, pushes the piston upwards and causes an increase in pressure in the positive and a decrease in the negative. A greater volume of the negative chamber facilitates the fork in copying the roughness because it helps to overcome internal friction, the pressure drop inside it will be more gradual and all this translates into less resistance, greater sensitivity in absorbing the impacts of holes and steps.
This also ensures more support mid-travel, which is where our forks work most of the time. The advantage of an air fork compared to a spring fork remains however the possibility of modifying the progression curve by varying the volume of the positive chamber with the tokens; these do not affect the first part of the travel, which will therefore always remain very sensitive, but modify the progression of the last 35%. To allow a finer adjustment of the latter, with TANK B1 and C1 is included the "Token.5", a token of volume equal to half the original Rock Shox, which therefore allows to obtain intermediate steps.