Hi guys,
I will be repeating some info here.
On the XR19-C
O-rings:
XR-19 Head:
Window seal - #019 EPDM (or the GID silicone)
Head to pak seal - #017 Silicone (red)
C pak:
Boot Seal O-ring - #016 Silicone (red)
Boot & Seal Retaining O-ring - #113 EPDM
XR27 & S27 Head:
Window Seal O-ring - 2 x 22 mm Buna (Nitrile)
Window retaining O-ring - #025 EPDM
Head to pak Seal - #017 Silicone (red)
27LT & 27LT-S head:
Window Seal - #023 EPDM
2x head to Pak seal - #017 Silicone
PD Piston:
Piston to sleeve seal - #015 Silicone (use #016 for added protection but stiffer activation)
PD head:
Window Seal O-ring - #019 EPDM
Head to sleeve seal O-ring - #017 Silicone
*******
Now as far as lubes go, there are incompatabilities galore.
Silicone seems to work with most synthetics and
most silicone greases. Petroleum based lubes can be a problem.
EPDM is good with all silicone greases and most synthetics that I am aware of. YMMV
If you get an O-ring from the hardware store, it is most likely Buna or Nitrile. I don't like to use this material but had to for size in the seal for the 27XR and 27S heads. It is OK as a seal and should it crack, you will see this. I couldn't find the metric O-ring in silicone or EPDM which I would have preferred. Buna (Nitrile) is subject to O-zone degradation, big time! If the material is kept lubed then you are OK. I have seen these in static, dry applications where they have failed. I encountered one in the guts of a SF a few years back that was in 4 pieces! :green: