Jockey cage hitting 2 x sprockets?

[DA-EVO]

Re:

The backplate on the derailleur is on upside down, it appears?

 

[cce]

mechs that short never work very well with sprockets over about 26t or so...

 

[FINNEY1973]

I have a different cage to that example, although the CTC measurements between jockey wheel spindles are the same - 4.8cm. Don't think it's on backwards; photo attached. As you can see the cage is pointing forward on 42T - 28T, which is most certainly not right! Might be easier to get a different cassette with a smaller ratio.

 

[cce]

the g-pulley should be the upper jockey wheel, it has float. And I too think that cage is on upside down.

 

[FINNEY1973]

Interesting - o.k leave it with me, i'll get the allen keys out & see.

Many Thanks

 

[DA-EVO]

I have a different cage to that example, although the CTC measurements between jockey wheel spindles are the same - 4.8cm. Don't think it's on backwards; photo attached. As you can see the cage is pointing forward on 42T - 28T, which is most certainly not right! Might be easier to get a different cassette with a smaller ratio.

As stated, the backplate is on upside down, definitely. Yours is designed differently to the picture but overall the design is the same in principle. The chain presses against the cogs when shifting, not the cage. note that the bottom of the cage on a derailleur is the one sorting out the chain line as the chain feeds back to the mech hence it needs to keep the chain controlled in both directions. the bit stamped 'g-pulley' should be at the pivot end. Campag, Mavic designs are also similar.

It won't work that way up.

 

[FINNEY1973]

Gents, as Borat once exclaimed: "Great Success". You're absolutely right, it was upside down. It's as smooth as silk now which I'm delighted about so many thanks for the input & the eye for detail. I'd got wrapped up in the technicals, rather than the basics. It still won't accept the 52T-28T option but I wouldn't ride that anyway, so it's a 15 gear bike.

Once again, many thanks & I'll be having words with the chap I bought the mech off

 

[gavr]

Re:

That's good - easily done swapping the jockey wheels and putting the plate back the wrong way round.

The spec on the RD6400 was min 12T and max 28T sprockets, max diff 28T so 52-42 out to be ok with a bit of fiddling...

 

[FINNEY1973]

Re:

Easily done indeed, I hadn't even considered it - another lesson learnt. Just wish i'd of noticed, I can't get those wasted hours back. At least my original set-up was correct, just with the glaringly obvious error on the mech. Such is life

 

[Little Al]

Hmm........."Slant Pantograph" mechs should be a bit more parallel to the chainstay than that.

Shaun

That was what I was about to suggest, looking at the photo the mech arm is not parallel to the chain stay Did you size your chain as big ring / big sprocket + 2 links, as a starter, on a lot of bikes in my pro mechanic days we often ended up with chain length = big ring/big sprocket +zero links Fiddle with your chain length to see if it cures the problem, so long as you get small amount of tension, on small ring, small sprocket, you should be good to go,& chain shortening will increase this anyway As an aside in the 82 worlds at Goodwood the USA time trial riders had to alter their inner chain ring size because of the weather conditions almost in the start house, on the small ring the bottom chain run looked like a superbike with the rear suspension fully compressed but they seemed not to have any problems in that respect.
Edited to say you have solved it