I recently purchased a used Trek 1000 equipped with Shimano 105 components, a Sachs LY 94 12-21 cassett mounted on a Dura-Ace hub.
When I shift down to the bottom two gears (12 & 13) the chain "jumps" as if it is trying to climb up the next gear, but it's not. As long as I have the bike on a stand spinning the wheel (with is no toruqe load), there's no problem. But I cannot ride the bike and shift onto these gears without the jump. I have no problems like this on the other gears.
I'm guessing it's a chain problem, but I don't know and would appreciate some help. The chain has the following markings stamped on the links:
UG
6F
VIA (I think, can't tell for sure)
Japan
Help please!
When I shift down to the bottom two gears (12 & 13) the chain "jumps" as if it is trying to climb up the next gear, but it's not. As long as I have the bike on a stand spinning the wheel (with is no toruqe load), there's no problem. But I cannot ride the bike and shift onto these gears without the jump. I have no problems like this on the other gears.
I'm guessing it's a chain problem, but I don't know and would appreciate some help. The chain has the following markings stamped on the links:
UG
6F
VIA (I think, can't tell for sure)
Japan
Help please!