Crankset & FD ghost shifting Issues - temporary 1x

wolfsbane2k

Hi.

Due to a FD cage failure, I'm currently running a double 105 5700 chainset without a front derailleur ( I've disconnected the cable to the shifter, and the cage has been completely removed), and let chain set in the smallest cog while I wait for the new FD delivery.

However, the chain catches on the pickups on the 50T and occasionally completely shifts over when I try use the smallest rear cog (11t) - I'm not sure quite what's causing this - I've taken the chainrings off and checked for flatness on a piece of glasss, and both are perfectly flat.

It's really quite dangerous; as much as I try and avoid shifting to the 11T, sometimes I forget, pedalling the cranks and the chain has flown up and over the 50t and wrapping itself around the pedal.

I really don't know where to look to next to try and stop this from happening - any help greatly appreciated.

Specs -
Crankset - 105 5705 34/50T
Chain - KMC -EL-10
Cassette - 4700 11-32T
RD - 105 5700
Hub/Freewheel - Shimano Tiagra (RoseBikes CX Wheelset)

photonic69

Set the limit screw on the Rear Derailleur so that it doesnt go into the bottom two cogs just to be sure. Simple and easy to do.

wolfsbane2k

PhotoNic69 wrote:

Set the limit screw on the Rear Derailleur so that it doesnt go into the bottom two cogs just to be sure. Simple and easy to do.

Ah, good hint to stop me shifting down inadvertently, thanks.

veronese68

A completely knackered chain wouldn't do this as it would have more side to side play, it would introduce a host of new problems though so I wouldn't advise it.
I guess from what you say the FD cage is FUBAR. If not, can you put the FD back on, locked in position by the limit screws, as a chain guide? The chain would rattle against it, but it wouldn't shift at the front.

timothyw

Yeah, you've basically discovered the reason that narrow-wide (and other 1x) chainrings exist.

Without the front derailleur cage in place they are liable to throw the chain.

On the plus side weird stuff like this happening while you are waiting for parts is an excellent reason to treat yourself to a second bike....

wolfsbane2k

Veronese68 wrote:

A completely knackered chain wouldn't do this as it would have more side to side play, it would introduce a host of new problems though so I wouldn't advise it.
I guess from what you say the FD cage is FUBAR. If not, can you put the FD back on, locked in position by the limit screws, as a chain guide? The chain would rattle against it, but it wouldn't shift at the front.

Yeah, the FD is completely fubar'd, the outer side of the cage has snapped off.

TimothyW wrote:

Yeah, you've basically discovered the reason that narrow-wide (and other 1x) chainrings exist.

Without the front derailleur cage in place they are liable to throw the chain.

It's only climbing out because it's hitting the shifting pins on the big cog though - this is something that's likely to be happening "normally" in that gear combo even If the FD is in place though. I can hear the "ping", "ping" as it hits the pins at a specific point in the pedal stroke.

TimothyW wrote:

On the plus side weird stuff like this happening while you are waiting for parts is an excellent reason to treat yourself to a second bike....

You mean a third bike... on it (viewtopic.php?f=40012&t=13095444)
Second bike's still waiting a headset bearing