Pulling a leader through a piece of inner tube has been a prescribed method for staightening a leader since as far back as I can remember and I've been fly fishing for about 56 years. It usually works but you have to pull hard enough to stretch the leader material and generate some heat. As Warren pointed out I believe heat is a major factor in the straightening process. If it doesn't work it probably means the leader material has "dried out" and should be replaced.
Hope this helps!
P.S. If anyone has a better way please chime in. Your never too old to learn!!!
Last edited by Redfisher; 01-12-2008 at 08:50 AM.