I'm getting tired of bumping this thread.
Ah, bumping the thread isn't the problem. You are being bothered by the bumping of the rim which prompts you to bump this thread.
Originally Posted by
ksryder
Here's my guesses -- either I'm damaging the tube with the levers when I remove the tire; or I'm pinching it when I seat that last little bit of the tire that's hard to get on even though I'm not using levers on that part.
I wouldn't want to disagree with rhm who has plenty of experience, but it seems not so likely that you are damaging the tubes when you remove the tire. In any case, you can test that by pumping up the tube a bit while it is off the rim just before you remount it. That's not a bad idea anyway because it verifies that you have a good tube before you waste time mounting a bad one.
You might be squeezing the tube between the tire bead and rim when you "encourage" that last bit of bead to go over the lip of the rim. I don't know what your usual procedure is but here are two key points. After you get the valve stem situated put enough air in the tube to help it hold some shape. This helps to stay up out of the way as you tuck it into the tire. Then as you go around the rim edging the tire over the lip, especially towards the last bit of length, push a tire iron up between the rim and tire to push the tube upward into the tire and away from the contact point between rim lip and tired bead. This is especially helpful if the tube is on the large side w.r.t. the tire and rim width, such as when using a 25-28mm tube with a 25mm tire on a 19mm (outer width) rim like the Sun M13-II.