Fitness Equipment / Exercise Machine Repair/Lifecycle 5500
Kerry G wrote at 2013-01-19 20:08:26
Hi, I wanted to add my insights re/ the "slipping" problem with the LifeCycle 5500 recumbant bike. My 5500 has had regular use for over 10 years and recently started slipping, generally when I'm pedaling aroung 70-75 RPM at resistance 5 or 6. The slip produces a pretty loud "chunk" sound and sure feels mechanical. I can produce it at will just with a forceable downstroke with either foot.
Per Mark Peterson's helpful instructions in this thread, I removed the cover (which, while slightly awkward, does not require removal of the pedals, by the way. But you do have to find the three screws hidden on the underside of the bike, facing down, to succeed) and examined the alternator belt. It seemed fairly snug, but I tightened it a little anyway---and that is not easy to do when you are working alone, especially if the belt is already fairly snug. It's hard to shift the alternator into the "tighter" position when a fairly snug belt is already pulling it in the opposite direction. Also, getting access to that alternator adjustment bolt required unscrewing a circuitboard assembly in my way. Moving the circuitboard also meant cutting a zip-tie which was tethering some wires. In addition, the pulley wheel on the alternator partially blocks access to the alternator adjustment bolt; and tightening that bolt with one hand while strenuously pushing the alternator assembly with the other was a chore.
While I had the bike housing off, I also examined/cleaned/oiled the chain, which was borderline rusty and pretty grungy-looking. One or two of the teeth on the big crank wheel looked a little worn down, but not enough to explain the skipping.
At that point I rode the bike with the cover still off. Still skipping. I was able to force a skip with either foot, one right after the other if I pushed hard enough. And skips only happened with that hard downward push, even with no resistance turned on---however, if I was careful to pedal with a perfectly uniform rotational speed and pressure, avoiding extra force on the downstroke, the skipping just about vanished, even at 80-90 RPM and resistance of over 6. So I realized there is something about that extra downstroke force which triggers the skip on my bike.
I got down on the floor and pedaled the bike by hand, watching the chain. This was illuminating: a hard downstroke pulls the top half of the chain taught, which simultaneously makes the lower half of the chain ---the part traveling from the bottom of the big crank wheel back to the sprocket on the alternator---go a little slack and saggy. The harder the downstroke, the more pronounced the slack. And the skip happens just as that saggy loop of chain heads into the alternator sprocket wheel.
Which leads me to believe that my chain has somehow become too loose, and when a hard downstroke makes the bottom length go extra-slack, it's not being picked up by the teeth on the alternator sprocket.
Never shortened a chain before, but thinking I will give it a try as I would hate to chuck this bike in the dumpster just yet.