Rich Koller wrote:
...snip.... I too bought a set of
rings from the Bus Depot (the German ones) and I found the same fitting
problem. It turned out that the rings were the correct size but you have to
fiddle with the fit in the groove so that the corregated segment doesn't
overlap itself and cause binding. I would line up the 3 pieces in the
groove and then carefully squeeze/compress them making sure the middle ring
didn't slip and overlap itself. .....snip....

I had exactly the same experience.  I first thought the rings were too big,
but comparison with the old rings showed they were exactly the same.

Bill