That depends on what is wrong with the rubber. If it is glazed, you
can clean it and continue to use it. If it is cracked or crazed, it
needs replaced. I recently paid $7 for a quart of deglazer at a local
printshop to clean the rollers on some printers, since I can't find new
rubber.
fair point - I have successfully resurfaced rubber idler tyres and
rollers, ( in vcrs, printers etc) often by just giving 'em a once-over
with fine sandpaper or an emery board. On more serious cases , on
especially hard-to-find parts (like idler drive 1960s record players)
putting the part in a lathe to rotate it 'evenly' as you 'sand' it is
a good way.
Anyway i digress - since we're talking belts here, I have found these
to be far less likely to respond well over the long term to
'rejuvenation' - best to replace, they're generally far cheaper than
idlers anyway
-b