How to fix a loose rubber focus ring?

[Peter S.]

I got two lenses (a MC Rokkor-PG 1.2/58 and a MD 2.5/100) where the rubber band around the focus ring had widened. For the 1.2/58 the situation is new, and thus it became loose only a very little bit. So fixing it has some time, but I am shure the need for repair will arise.

The one of the 2.5/100 is widened a lot - it need to be fixed before starting to use the lens.

Do You got any special tricks to shrink the rubber? Heat? Water vapor?
A two sided adhesive band might do for the better one, but I had to cut the bad one, to remove a few millimeters of the band, which is a irreversible action - thus I seek Your advise.

Many thanks in advance!

Best regards
Peter

[Peter S.]

lost my patience, did cut out 8mm and used some epoxy to glue the thing
back to the lens. The state of the lens is as bad as B-C. I would not want
to do this on my 1.2/58...
P