Hello all,

Something disconcerting happened before and during a ride this past weekend, and I'm hoping for some input. Here's what occurred:
Being a shrewd observer of the obvious, when I got the tandem down (it lives vertically, with the weight on the rear tire and the front wheel secured by a hook) for a ride I immediately noticed that the rear tire was completely flat. This seemed peculiar as it had been fine when put away, but I figured a slow leak was probably the culprit. So I tried pumping it up as a first step. I heard the air coming straight out and after (too easily) removing the tire found a tear in the tube at the base of the valve. I got new tube out and put it on. I pumped it up to the recommended pressure (95) and set it aside as I put the pump away. One thing led to another by the time I came back from putting the pump away probably 10 minutes had elapsed since I had left the wheel leaning against the wall. I was at the bike preparing it to accept the wheel and… BOOM!! The tire had come off of the rim and the tube of course exploded. I figured I had made some sort of mistake in mounting the tire, but was leery about how loose the fit was. So I got out a new tire (and tube) and put it on. This went on pretty easily too, so I was extremely careful to make sure that it was evenly on the rim. I inflated slowly and stopped several times to adjust to make sure everything was perfect. Once fully inflated (105 for this tire) I bounced the wheel/tire around to see if I could induce any problems that were thinking about showing themselves. Everything seemed okay, so I mounted the wheel, finished preparing and off we went. We rode about 12 miles to breakfast, took about an hour to eat and then continued on our way. Less than 10 miles from there, another boom. Same thing. Fortunately we were going easily, up a mild grade, in a straight line and so there was no real danger. I replaced the tube, pumped up to only about 75 psi, and we carefully made our way home without further incident. So now, I’m afraid to even ride the thing. The rims are the standard Firs that came on the 2002 Santana, and the tires are folding Panaracer Paselas that I got after reading good things about them here on the forum. I started out with a 32mm on the rear, but the spare was a 28, the original size, so while I don’t know the inner width of the rim I don’t think it could be a size problem. Tangentally, we just returned from the Icefields Parkway in the Rockies so I am really, really glad that this didn’t happen while on one of those descents.
I’ve more or less decided that I can’t use those tires on those rims, but this still seems weird. 700c tires should go on 700c rims, right? Can someone explain to me what might be going on here?
And I guess more importantly, what to do going forward? My sweetie/stoker popped in to a LBS to ask advice and as they specialize in Specialized, see about getting some Armadillos, or Gatorskins. When she was explaining the situation, as soon as she said ‘tandem’, the guy said “Is it a Santana?” and when she replied “Yes” he said, “Don’t get the Armadillos. Go with the Continentals.” So he steered her away from their $60 tires to some half the price that they don’t even sell. (you gotta appreciated that kind of salesperson) What does he know that I don’t about Santanas (Fir)? What do you all know that I don’t know about Santana (Fir)?
So I ordered some Grand Prix 4 Seasons because I couldn’t find 28mm Gatorskins with Kevlar beads and I want to be able to pack one as a spare. Only after placing the order did I start to think about the folding bead as a source of the problem. I have searched here and found only one example (with unknown tires) that matched our ordeal almost to the letter, but many saying folding tires should work just fine. Even so, now I’m second guessing myself, and I have some questions.
Are Firs known to be on the small side?
Are Paselas known to be on the large (loose) side?
Are folding bead tires less secured than wire bead ones (all other things being equal)?
If a tire is really easy to get on a rim, is it likely to be blown off?
Conversely, if a tire is difficult to mount, is it less likely to be blown off.

Any enlightenment would be greatly appreciated.

mandd