Just got back from a trip and found this thread of around July 1-2
about removing old rubber from tracker bars.  I'm afraid I can't offer
much regarding how to do it properly.  I can, however, offer good,
free advice on how _not_ to do it!

I had pulled the wooden tracker bar from my 1901 Simplex pushup, which
had petrified rubber on the nipples.  Somehow I figured out the rubber
would soften in water, so I put a half inch of water in the sink, and
stood the tracker bar in the water, nipples down, with the wood safely
above the surface.  And then I left the house for the day.

Big mistake -- looks like my momma did indeed raise a dummy.  The rubber
did soften, and the tracker bar fell into the water, and delaminated.
It cost me a day to reglue it and clean out the (square) holes.

Ray Fairfield