One other thing, are you sure the flats are caused by the tire sliding off the rim, the classic "blow off" flat? When this happens, usually there is a section of the tube outside the tire/rim, where the tire bead pulled off the rim. Or else there is a long tear in the tube. I presume the sidewall of the tire didn't split or explode. You usually only see the blow off with excessive pressure and a bad mix of rim holding power and stretchy beads. This is why you don't use kevlar beaded tires (stretchy) on straight, non hook walled rims (less holding power). If, however, your rims have the same bead/hook as the Bicycle Quarterly repro 58 style rims, this shouldn't be a problem.
If instead you had two closely located holes in the tube, this might be the classic "snake bite" pinch flat, caused by too low of air pressure and hitting a sharp edge like a pot hole or train tracks. Of course a single hole and a slowish leak means a straight puncture flat, check the inside of the tire for glass or debris.
The rim tape check is also a good tip. I once had a series of flats with an OCR Bontrager Clyde rim, trying to get by with a 17mm rim tape instead of the necessary 22mm. The tape would squirm away from the eyelets, and Pop! another tube bites the dust. If your rims are copies of the super champ 58s, then the proper rim tape is 10mm, extra narrow to fit in the channel over the spoke heads. This style rim is vulnerable to too long of a spoke, because without the double wall, the too long spoke will poke up into the tube and cause flats, albeit in a single spot on the tube. You then go crazy trying to find the piece of glass when in fact it's the spoke.
If the tire is pulling off the rim, then the tube should show some major damage.
Tom Adams
Manhattan, KS USA
From: David Snyder <dddd@pacbell.net> Subject: Re: [CR] re : Panaracer Pasella 27x 1 1/4 sidewall blow-outs (AT) 50psi To: classicrendezvous@bikelist.org Date: Sunday, March 21, 2010, 9:20 PM
I note that there is a bit of variation in tire fit, differences in tires and differences in rims, but this sounds like a too-severe case. I would start with a bit of air in the tube, letting air out (as will be usually be needed) during installation. This helps to prevent the tube being trapped under the bead, as Mike mentioned. I put tube in tire before putting tire on rim, and get the tube centered within the rim before starting to fit the second bead. My Kevlar Paselas do seem particularly easy to install. I run only 60psi in a generously-sized tire like the 1-1/4"-sized Paselas. I have known wire-beaded Kendas to push over a plain rim's sidewall at just under 90psi, but have run other tires (not the Paselas) at that pressure.
A narrow rim necessitates a bit higher pressure to prevent pinch flats with the same tire. A wide tire on narrow rim may need help with the valve stem coming up during inflation, so I give it a tug before inflating in ernest, lest the tube tear in the valve stem vicinity as the tube expands into the rim cavity.
I have also seen (I have a pair) Sun rims with 700c label that are really 27". Threw me for a loop.
David Snyder Auburn, CA usa
----- Original Message ----- Subject: [CR] re : Panaracer Pasella 27x 1 1/4 sidewall blow-outs (AT) 50psi
>
> At a shop I worked at we got a pair of Sun CR-18 rims that were marked 700,
> but actually were 27"...
>
> You shouldn't get blow-off at such low pressures unless you are trapping the
> tube between the tire and rim....
> Mike Fabian