Originally Posted by
stokessd
Yes, and the last time I watched it too as best I could. I thought for sure that it was my freehub (DT hugi) and I was all set to return from the ride and tear it down. We are able to replicate it in the middle chainring and the middle of the rear cassette. The cranks are Truvativ (which are pretty crappy), and the cassette is a 9 speed ultegra (12-25). The chain is a shimano 9 speed unit with about 500 miles on it. I just replaced the timing chain with one just like it about 150 miles ago and the measure the same.
The frustrating thing is that I can't make it do it with just my power alone, so I can't go out and watch closely. My wife's feet and legs are typically in the way.
There is what feels like a freewheel slipping a ratchet location, but the distance is one chainring tooth, or a multiple of them. When it happens I see the chain jump on the middle chainring. I was thinking it was inertia from the freeing up then catching if it was the freehub. But the fact that we can't make it do it in the big chainring (with a bigger cog in the back for the same gear) is pointing to the something other than the freehub.
I've been riding and a bike mechanic since the early 80's and this has me stumped. IF the chainring teeth were shot, I'd be a lot less confused, but they look good.
Sheldon
You sound like you have a good understanding of your driveline. I also have a Cannondale with the same group set, a 2005 RT. I still think it may be your R/D or the free hub. But, I guess anything is possible. You might also check your chain length and your "B" adjustment, just in case she's jumping between rear cogs. On mine, the "B" was way too "open." After dialing it in, it shifts much better.
I agree, these SDI set-ups can be frustrating, especially on a tandem. I can't believe the difference between my 1/2 bike and our tandem, both with Ultegra shifters.