I've had similar problems using steel and Kevlar-beaded tires on older Araya rims, with similarly semi-circular (not hooked, really) bead seats. It only happened following heavy braking on descents, where some slight pressure rise, along with bead expansion combined to push off the bead. It always involved the front tire, which was run at modest pressure, around 100psi for a 20-23mm tire.
With a Tandem, there's the chance to really heat up the rims, and the additional spokes might even have some diameter-reducing effect on the rims. Since the 27" GatorSkins are steel-beaded, I could only suggest using the similarly armored, same-sized Armadillo tires, hopefully a little smaller bead diameter. The only tire I've had come off a mod58 rim was a Kevlar-bead Michelin Elan. I used the old Turbo tires for years in 1-1/8" and even 1" sizes and never had problems on 58's with those.
The only other recommendation would be to ensure that the bead seats evenly during inflation. The 1-3/8" Michelin HiLite Tour tires on even a well-hooked Mod-4 rim are very sensitive to that on my touring bikes, and I rarely go over 60psi. I stop pumping at about 10psi and work the bead up with my hands, then pump to 30psi. After a few minutes I take 'em up to 60.
David Snyder
Auburn, CA USA
>I can't seem to inflate Conti Ultra Gaterskins on my 27" Super Champion 58
>rims above 90 psi without the tire blowing off the rim. It is on a tandem
>so 120 psi or so would be nice (we are no an especially lightweight team).
>Has anyone found a modern tire that will stay on this rim at these
>pressures? The SC 58's seemed to be a quasi hooked bead rim. I think that
>I recall that Conti Sport 1000's were a bit better at staying on at higher
>pressures but were more flat prone. Any tricks to getting the tire to stay
>put? Classic content are the rims and the bike, a '73 Jack Taylor curved
>tube tandem.
>
> Thanks!
> Paul Raley
> Nice riding weather in Leonardtown MD