Chain jumping on lower jockey wheel

Scotty-Gee

Build up my TT bike today.

Brand new frame and hanger, new rear 105 derailleur, Q rings with less than 500 miles on them. Chain with less than 200 miles (pretty sure it's a ten speed)

The shifting is super smooth right up until the top two biggest cogs on the rear cassette. I think it's an 11-25 or 28.

In these two gears the lower jockey wheel appears to be not meshed with the chain and it's makes a terrible noise.

Suggests on the net seem to be a bent hanger but I don't think this is the case.

Why does it only happen in these two gears?

How do I fix it?

brownbosh

stiff link
chain too short
or jockeys wrong way around.

rolf_f

If you have built a TT bike and don't even know if your cassette is a 25 or a 28 then the best way to fix it is to take it to an LBS

Might be the b limit screw - how close is the top jockey wheel to the cassette when in the biggest cogs?

That doesn't explain the issue with the lower jockey wheel. Can't really work out why that would happen given the new everything; the problem is associated with the biggest cassette sprockets but manifests itself in the jockey wheel that isn't next to the cassette.......

rayjay

Have you checked the jockey wheel to see if it is loose?

manglier

+1 for the B screw adjustment. View this, http://www.youtube.com/watch?v=wQncKmddahk

sungod

not trying to be nasty, but if you don't know the range of the cassette or which type of chain you have, it seems possible that you've got something fundamental wrong...

i) what's the total capacity of the drive train vs. the specified capacity of the rear mech?

ii) is the chain length correct?

for both of these, refer to the correct instruction sheet (packed with the rear mech, or get it here: techdocs.shimano.com ), 105 5700 or 105 5700-A, it makes a difference

Scotty-Gee

It's an 11-25 sprocket.

It seems to have resolved itself after checking the chain over and some lubrication. I can only assume a stiff link.

Thanks for the help all.