FINNEY1973
Senior Retro Guru
Slightly perplexed by this one. Apart from this issue, I've just finished putting together a build consisting of Shimano 600 Tricolor group with the exception of the BB, which is a generic UN55 as I haven't been able to source a tricolor BB in decent condition. The cassette is also a modern offering being a HG-50. Teeth range is 11-28T (I think 12-28 would have been a better option is the 11T cog is a bit clunky).
Having looked at the max cog size & chain wrap and looked at other peoples builds on the www, most had suggested that it is possible to have a 28T rear sprocket without issue. I've played around with cable tension, chain length and the gearing is sweet with the exception of two rear sprockets. Oddly it isn't the 28T sprocket which if there was to be an issue I'd of thought it would have been this sprocket.
The rings up front are 52 - 42, it's a 6401 8 speed derailleur in conjunction with 600 STI's. It should work, but it doesn't.
The issue is the upper part of the jockey wheel cage is hitting the adjacent sprocket when on the 21T & 24T sprockets (which are 2nd & 3rd on the cassette if the 28T is the first sprocket). In the troublesome gears, the angle of the junction where the derailleur connects to the jockey cage is under more tension than in the other gears. Chainline is bang-on so this isn't an allignment issue.
All a bit odd, I wonder if I could tap the minds of those who may have some diagnosis or advice. I spent 4 hours yesterday tinkering with this, my patience has run out i'm afraid to say.
Cheers
Having looked at the max cog size & chain wrap and looked at other peoples builds on the www, most had suggested that it is possible to have a 28T rear sprocket without issue. I've played around with cable tension, chain length and the gearing is sweet with the exception of two rear sprockets. Oddly it isn't the 28T sprocket which if there was to be an issue I'd of thought it would have been this sprocket.
The rings up front are 52 - 42, it's a 6401 8 speed derailleur in conjunction with 600 STI's. It should work, but it doesn't.
The issue is the upper part of the jockey wheel cage is hitting the adjacent sprocket when on the 21T & 24T sprockets (which are 2nd & 3rd on the cassette if the 28T is the first sprocket). In the troublesome gears, the angle of the junction where the derailleur connects to the jockey cage is under more tension than in the other gears. Chainline is bang-on so this isn't an allignment issue.
All a bit odd, I wonder if I could tap the minds of those who may have some diagnosis or advice. I spent 4 hours yesterday tinkering with this, my patience has run out i'm afraid to say.
Cheers