Originally Posted by
onespeedbiker
Your photo shows the left cup not bottomed out on the cartridge; it should be covering the shinny ring, which is a cartridge bearing and is pressed in when you tighten the left cup.
I thought I had pushed it all the way on when I held the thing against the frame. The cup slides back and forth easily enough. There's a bit of air trapped in there though, and it pops back out like in the photo when I'm not holding it.