Originally Posted by markanddebbie
About 500lbs together.Should we be concerned about bending the frame,spokes,or bridges?
In general, the older Schwinn tandems were pretty beefy bikes. However, at 500# you may approaching the upper limits if it is a double step through, "Schwinn Twinn". For reference purposes, the basic "Twinn" sold in the 70's and early 80's had both a front and rear step-through frame, whereas the captain's cockpit on the Twinn Sport model added a horizontal top tube that made the frame a bit more robust. As a visual point of reference, here is a link to a page from the '79 model year catalog that has pictures of both frame styles: http://www.geocities.com/sldbconsume.../79ccpg44.html
Obviously, the true test is how comfortable you both feel riding the bike. If the frame doesn't feel like it's twisting under your weight (aka, noodly or wagging it's tail), then it's "stiff enough". However, if it feels like its twisting, then it probably is and that would cause me some concern as the bike could prove difficult to control in certain situations. As for breaking the frame, if the frame is free of rust or damage, that's probably not an issue. Wheels I address below....
Anyway, not knowing the condition of the bike, if you are having a bike shop do a once over and repack the bearings I would ask them to:
1. Inspect the inside of the handlebars, fork steerer/crown, head tube, seat tubes, and bottom brackets to verify that the frame did not have anything more than what would be the usual amount of surface rust for a bike of that vintage. This is to verify the integrity of the frame.
2. Inspect the fork and frame's alignment and otherwise give the frame a good once over for signs of any previous damage. This is to ensure the tandem will handle properly. A bent or twisted fork, as well as any rear frame alignment issues can have adverse handling implications. On the bright side, it's relatively easy to realign older steel frames like these. A previously bent and realigned fork is an entirely different issue all together and would warrant further inspection by a frame shop.
3. Have them remove and replace the tires with the largest diameter tire that the rim will allow and have them also inspect the rims while the tires are off for any signs of rust, corrosion, or damage. Finally, have them true and retension the spokes. These steps should ensure the integrity and durabilty of the wheels.
4. Have them pay particular attention to the brakes. My real concern here would be that you avoid any steep descents with this bike. The brakes are most likely inadequate for even most moderate to long downhill descents where a lot of braking power with high heat capacity would be required to control your speed. Even if you were to buy a brand new $5,000 tandem I would note that the "standard" brakes on most models would be inadequate and an auxiliary Arai drum brake would be required. For bike paths and similarly level pavement, the original brakes once tune-up and fitted with new pads "should" be just fine.