Chain slipping _between_ chainrings

[walser]

On my TT bike, when the chain is on a sprocket on the outer half of the cassette, the chain slips between the chainrings when I try to go from big to granny. I have to go to a sprocket on the inner half of the cassette before the chain will get onto the small chainring.
The problems started after I went from 9sp to 10sp chain (on a 9sp FD).What do you think causes this problem?
a) using a 10sp chain with a 9sp FD,
b) new chain on old chainrings,
c) bad adjustment,
d) something else

 

[gclark8]

The space between the rings in less on a 10 speed crankset.

Use all 10 or all 9, don't mix.

 

[thomas_cho]

On my TT bike, when the chain is on a sprocket on the outer half of the cassette, the chain slips between the chainrings when I try to go from big to granny. I have to go to a sprocket on the inner half of the cassette before the chain will get onto the small chainring.
The problems started after I went from 9sp to 10sp chain (on a 9sp FD).What do you think causes this problem?
a) using a 10sp chain with a 9sp FD,
b) new chain on old chainrings,
c) bad adjustment,
d) something else

I cant see how the chain can be between the chainrings ... do you mean that the chain is dropping off the small chainring? Your front derailleur may not be moving enuf to shift the chain correctly, try adjusting the FD first.

There is also a part that you can clamp on to your seat-tube that can stop your chain from dropping. See attached pict.

FWIW I have mixed 9&10 spd parts, generally with no dramas.

 

[walser]

The chain is not jumping off, I'll try to express myself better

This is what happens (from sheldonbrown.com/dura-ace.html#alternate):
" "Skating" occurs when a narrow chain is used on a crankset intended for a somewhat wider chain. In downshifting, instead of the chain meshing properly with the teeth of the inner chainring, the side-plates of the chain can ride along the tips of the teeth of the small ring. This causes a momentary "freewheeling" forward. " In my case, the skating is not momentary. The chain will skate until I go to one of the 4-5 biggest sprockets on the cassette.

The site also says:
" The difference between "9-speed" cranksets and older models is only in the inner chainring. The teeth on a "9-speed" inner ring are slightly displaced to the right to better accommodate the slightly narrower chain. "

Does anyone know if the teeth on a 10sp inner ring is further displaced to the right compared to a 9sp inner chainring, or if it is the crankset itself that has changed?

 

[nerdag]

Does anyone know if the teeth on a 10sp inner ring is further displaced to the right compared to a 9sp inner chainring, or if it is the crankset itself that has changed?

Apparently, yes (this tip is courtesy of one of RBR's newsletter's). The difference is about 0.6mm, so if you stick a 0.6mm chainring spacer between the inner ring of a 10s crankset and the spider, you should make it work fine and dandy with a 9s chain.

n