The casting on the spring side acts as a positive chamber with zero air pressure preload but high compression ratio. Initial volume is huge but compressed is quite small (unlike the damper side, which has a very low compression ratio, therefore its effect can be considered almost zero. This is why the Everflow Airlink works). The pressure generated pushes against the air spring seal head at the bottom of the stanchion, which acts as the "piston".
The buttercup occupies a small fraction of the initial volume but a much larger percentage of the compressed volume -> compression ratio increases -> pressure increases
The shaft of the LF is designed to protrude in the lower leg only with the narrow foot stud when fully compressed, so volume is amost unchanged. But when fully extended the large shaft takes a lot of volume. Less initial air compressed in the same volume -> lower compression ratio -> lower pressure.
The larger shaft decreases the surface area of the seal head "piston", so total bottom out force is decreased even more (Force = Pressure X Surface, here both P and S are decreased)
A measurement of this effect was done only on a previous generation Lyrik with a 160mm Debonair C1 spring. The reduction was about 10kg, 40% less than the stock spring.
This effect is fixed, doesn't change with air spring pressure. A 100kg rider might not notice it at all, while for a 60kg rider it could mean 5-10mm more usable travel.
The difference is amplified with longer travel, and also in comparison to Debonair B1 spring (because of its flat seal head) and Buttercups. On a 190mm ZEB, compared to the Debonair+ with buttercups, the difference should easily exceed 20kg (and I'm being very conservative here, because I don't like to pull numbers out of nothing)
The buttercup occupies a small fraction of the initial volume but a much larger percentage of the compressed volume -> compression ratio increases -> pressure increases
The shaft of the LF is designed to protrude in the lower leg only with the narrow foot stud when fully compressed, so volume is amost unchanged. But when fully extended the large shaft takes a lot of volume. Less initial air compressed in the same volume -> lower compression ratio -> lower pressure.
The larger shaft decreases the surface area of the seal head "piston", so total bottom out force is decreased even more (Force = Pressure X Surface, here both P and S are decreased)
A measurement of this effect was done only on a previous generation Lyrik with a 160mm Debonair C1 spring. The reduction was about 10kg, 40% less than the stock spring.
This effect is fixed, doesn't change with air spring pressure. A 100kg rider might not notice it at all, while for a 60kg rider it could mean 5-10mm more usable travel.
The difference is amplified with longer travel, and also in comparison to Debonair B1 spring (because of its flat seal head) and Buttercups. On a 190mm ZEB, compared to the Debonair+ with buttercups, the difference should easily exceed 20kg (and I'm being very conservative here, because I don't like to pull numbers out of nothing)
