Originally Posted by K&M
What kind of pressure do you run in your 25s and 23s? The Rolf folks say never to put in more than 120 lbs. when using their high-zoot tandem wheels, regardless of what kind of tire you're running. And what about the size of the rim? I understand from posts on other threads that some tandem rims are too wide for 23s. I hope this isn't a problem with the Rolfs.
Rolf wheels... that's a new data point in this discussion and, yes, Rolf does specify a 120 psi limit as well as a maximum tire width of 28mm for their rims. Of course, they also incorrectly state that drum and disc brakes installed on tandems are only to be used as drag brakes to supplement the rim brakes; oops.
To your questions:
700x23 Vredestein Fortezzas are normally run at 140 - 145 psi.
700x25 Vredestein Fortezzas are normally run at 130 - 135 psi, but dropped down to 115 - 120psi when road conditions demand a more compliant tire, e.g., chip-seal in Texas, Virginia, etc...
As for rims, we use 700c Velocity Deep-Vs which, according to Velocity, will handle any psi currently offered by tire manufacturers. We have used the Velocity rims exclusively on both road tandems since '02 -- perhaps 10k miles or so -- with no issues or even any hints of a weakness and have ridden away from some fairly nasty pothole encounters at 25mph with only dented rims (Note: pacelines are dangerous when the lead riders don't call out obstacles & hazards).
The key to figuring out if a given rim is acceptable for use with a given tire is the inside bead seat diameter, not the overall rim width. For example, our Deep-V's have an outside rim width of 19mm and an inside bead width of 14mm; ideal for our 23's and 25's but near the margins for a 28. Velocity's Dyad rims -- sold as OEM on some Co-Motion tandems -- have an inside bead width of 18mm which is marginal for a 25mm tire; however, I've seen a bunch of tandems with Dyads running 25mm tires over the years so 18mm "seems" to be about the upper limit 25's; 23's would be a stretch.
A good nominal inside rim width compatibilty table can be found at Sheldon Brown's Website:
http://www.sheldonbrown.com/tire_sizing.html#width
Of course, tire sizing is sometimes an inexact science, e.g., Continental's tires have tended to run small and earlier models of the Vredestein's seemed to run big. Anyway, you get the idea; it's always a good idea to search out the inside bead width of rims before buying to make sure they are suitable for any of the tires you plan to run.