mikewhiskey

Very new to fixing bikes. Picked up a '98 Cannondale today with a shifting issue. When trying to shift, something catches and I can feel a tug on the cable. However, the cable does not remain in the position it is pulled to nor does the rear derailleur seem to react. The catch (and the noise in the video) do not feel like it should when shifting. It feels like it's trying to engage the shifting mechanism but it encounters too much resistance. I've de-gunked the shifting mechanism with some WD-40 but I'm not certain as to the origin of the problem. Has anyone else experienced a similar issue?

Poorly filmed video of the problem:
youtube (.com)/watch?v=FVtvx-zKzCc

HillRider

I assume these shifters are STIs. Old, and these are truly old, brifters do tend to get clogged up with hardened grease and dirt. The most common approach is to soak them in Odorless mineral Spirits (OMS) for several hours with frequent agitation to wash out the crud, then dry them thoroughly followed by a lot of thin oil. If that doesn't work you have to assume the internal mechanism is just worn out from use. There are no repair or replacement parts available and the only alternative is replacement.

One other thing is to inspect the cables and housing. If they are frayed or worn that will contribute to bad shifting too.

AeroGut

I would first try to isolate the problem. First try moving the DR by hand to make sure it works. Then try pulling on an exposed part of the cable near the DR. Does the DR move? If yes, then unhook the cable and pull it back and forth in the housing by hand. Does it move freely? Then try shifting the brifter in both directions while pulling gently on the cable. Is it taking up and releasing cable at all?

That way, you can identify if the problem is the shifter, the cable and housing, or the derailleur (or some combination thereof).

mikewhiskey

It seems to be isolated to the shifter, very likely gummed up but I can't seem to take it apart due to the grub screw being lock-tighted down. It pulls on the cable and releases it, but the cable returns immediately to the position it was before trying to shift. However, I was unable to move the rear derailleur when pulling on exposed cable near the derailleur. It seemed to be locked in place.

AeroGut

If you're unable to move the derailleur by pulling the cable by hand, it could be that the shifter is fine and just can't pull enough cable to get to the point where the ratchet engages. Unhook the cable from the derailleur and check if the shifter works when not attached to the derailleur. You can also check if the cable moves easily through the last bit of housing before the derailleur. You might be trying to fix the wrong thing.
For the derailleur, does it move if you just push it by hand (towards the larger cogs)?

mikewhiskey

Yeah, just confirmed it to be the shifter. The derailleur can move side to side and the cable can move freely in the housing. Even when I took unscrewed the cable connector from the derailleur, the shifter would not shift up or down. I'm gonna get some lock-tight remover, take it apart, clean it, and see if it works from there.

Ironfish653

Sorry i'm late to the party, but I've run in to a similar issue on other STI 'brifters' from that era. RSX and RX-100; That if you 'dry fire' the shifter, ie; shift up and down while the pedals aren't turning, that the end of the cable can unseat and foul around the 'drum' inside the shifter.

It kinda does as you describe, it'll pull the cable in, but then you can pull it right back out. There's not enough clearance for the cable end to pull out of the shifter body, so working the shifter 'through the gears' ends up snagging it and dragging it back into the works.