Limiter screws assistance required for the granny ring

phreak

Hi all,

I had a situation on my ride today where the chain went too far when trying to put it into the granny ring and lodged firmly the other side (had to removal the whole chain and put it back on again to resolve it).

It's clearly a limiter screw issue, but, I can put it perfectly into the biggest sprocket when in the big ring, so it's only the small chainring that provides an issue.

What do I need to play around with?

sungod

there are two limit screws, if the cage is moving too far inwards you need to use the lower limit screw to adjust it out a bit

bear in mind there can be other causes, for instance a bent fd cage, misaligned fd, damaged chainring etc.

generic adjustment instructions...

http://www.parktool.com/blog/repair-hel ... adjustment

phreak

sungod wrote:

there are two limit screws, if the cage is moving too far inwards you need to use the lower limit screw to adjust it out a bit

bear in mind there can be other causes, for instance a bent fd cage, misaligned fd, damaged chainring etc.

generic adjustment instructions...

http://www.parktool.com/blog/repair-hel ... adjustment

So it's an issue with the screws at the front, not the back? Out of interest, why would it not happen when in the big ring?

trailflow

The front and rear derailleur are totally separate. So you dont need to adjust the RD.

Put the chain on the inner ring and biggest cog on cassette (easiest gear). Look at the inner FD cage and then turn the low limit screw (the screw closest to the frame) on the FD inwards until the inside of the cage is around 0.5/1mm from the chain

If the gap between the inner cage and chain is any bigger it will over shoot when shifting down from the big ring and throw it over the inner ring.

Same with the big ring. If the high limit screw is too far out. The cage will move too far (when shifting from the inner ring to the big ring) and throw the chain over and off.

The limit screws limit how far the cage can move to prevent overshifting at each end.

If the big ring is not overshifting then that suggests it is set up correctly. There is no need to touch the high limit screw.

phreak

trailflow wrote:

The front and rear derailleur are totally separate. So you dont need to adjust the RD.

Put the chain on the inner ring and biggest cog on cassette (easiest gear). Look at the inner FD cage and then turn the low limit screw (the screw closest to the frame) on the FD inwards until the inside of the cage is around 0.5/1mm from the chain

If the gap between the inner cage and chain is any bigger it will over shoot when shifting down from the big ring and throw it over the inner ring.

Same with the big ring. If the high limit screw is too far out. The cage will move too far (when shifting from the inner ring to the big ring) and throw the chain over and off.

The limit screws limit how far the cage can move to prevent overshifting at each end.

If the big ring is not overshifting then that suggests it is set up correctly. There is no need to touch the high limit screw.

Just to confirm here, the chain didn't jump off when moving from the big to the small chainring, it jumped off when in the small chainring and moving onto the biggest sprocket on the cassette at the back (ie the lowest gear). It went into that gear perfectly when on the big chainring, but not on the small one.

As it seems to be moving reasonably between the two chainrings, is it a problem with the front derailleur? For reference, it is also shifting perfectly well in every other gear.

trailflow

No it's not the FD then. Your wording in your original post made it seem like you were talking about the FD.

If the chain moves past the big cog and into the spokes then the low limit screw on the RD needs adjusting.

Put the chain on the inner ring and big cog. Turn the Low limit screw on the RD inwards (the screws should have the letters L and H next to them)
Look at the top pulley teeth and align it directly inline with the teeth of the big cog. Push the RD body by hand to check it doesnt go any further and cannot go into the spokes.

The reason it doesn't do it on the big ring is probably because of the chain angle pulling the chain away from the cog. Im sure if you kept doing it for long enough it would eventually fall into the spokes at some point.

Using the big/big combo is cross chaining anyway so probably best to avoid that combo. As it will cause premature wear of the chain. It also is the noisiest gear combo. Another reason not to use it.

phreak

Apologies for not being clear in my original post. I'll give that a tweak tomorrow and see how it goes. Thanks for your help.