If they're the same as the sram hidden bolts then you should be able to knock it out. Just find a rod the right diameter, support the ring from the underside and hammer it out.
That would have been better than the approach I took which was to re-thread the sleeve to push it out only to have to use pliers to separate them again.
If they're the same as the sram hidden bolts then you should be able to knock it out. Just find a rod the right diameter, support the ring from the underside and hammer it out.