The last update to RockShox’s Pike, Revelation, Lyrik, and Yari forks was just a change to the C1 air spring with a new foot nut and seal head. I believe this was done as a response to complaints from users that their forks were sagging into the travel and so had less travel than advertised. A 160 mm fork might have been sitting at about 155 mm at rest, for example. RockShox has touted the revision as providing a higher ride height and no wasted travel or dead space. However, suspension specialists (such as Chris Porter and Vorsprung) have pointed out that the C1 seal head creates a smaller negative air chamber, resulting in a less supple start to the travel and less small-bump sensitivity. Their recommendation seems to be to stick to the B1/B2 seal head and enjoy the better grip and sensitivity at the top of the stroke, and stop obsessing over the travel markings on the stanchions.
Based on my understanding of how the system works, it’s the longer foot nut of the C1 version that extends the fork out so it has more travel and is riding higher. It is equivalent to fitting a slightly longer air shaft. I can only hypothesise that the seal head was revised in order to reduce the negative air volume so that the fork cannot be extended deep into the negative travel to the extent that insufficient stanchion and bushing overlap become an issue. Is anyone able to confirm this, or correct me, please?
If I am right, does that mean that one could use the longer C1 foot nut to get the higher ride height, but combine it with the B1/B2 seal head for the large negative chamber, provided that the fork is not already at the maximum travel for that model? So with a 160 mm air shaft in a Lyrik and a 140 mm air shaft in a Pike this should be fine, and would give the advertised travel but also the superior performance of the larger negative air chamber?
Any clarifications, corrections, or references to further reading or explanations are appreciated!
