Dropping chain

daviescgwen

Hi I have an Ultegra 8000 groupset. I’m having issues with the chain dropping at times on my rides.
It happens when I’m changing gear on the front derailleur from 50t down to 34t and the chain rattlles and sometimes gets trapped between frame and crankset. This has caused some damage.
It only happens when I’m in the middle of the rear cassette gears which is the strange part. It’s fine at the top and bottom gears.
My chainrings have done 7000-8000 miles, could it be a worn or damaged tooth on the front 50t chainring?
Thanks

de_sisti

I would imagine the H / L limit screws on the front derailleur need adjusting.

daviescgwen

Unfortunately it’s not as simple as the H\L adjustment. This is correct, when it has slipped its pushed the front derailleur and the chain catcher out of the way.
H/L screws are in the correct position and I’ve had it checked with a bike mechanic as this was my first thought.

i.bhamra

Not sure I understand what you mean by pushing the FD and chain catcher out of the way. The FD should not be able to move further than the point set by the low limit screw? Was the limit set with no tension on the FD ie cable should be detatched or have plenty of slack in it when setting? Other possible explanation - is there any movement where the FD is bolted to the frame such as a loose bolt or damage to the braze-on/adapter?

wongataa

I would be taking the cable off the derailleur and setting it up from scratch making sure I followed the Shimano instructions to the letter.

trevor.hall12

daviescgwen said:

Unfortunately it’s not as simple as the H\L adjustment. This is correct, when it has slipped its pushed the front derailleur and the chain catcher out of the way.
H/L screws are in the correct position and I’ve had it checked with a bike mechanic as this was my first thought.

I doubt it's correct ,but it needs set up from scratch .
Only thing it could be if it's not tge limits is the angle ,is it parallel with the chainring ?

daviescgwen

Thanks for the replies. I’ve had a closer look and also noticed that as the chain makes contact with the chain ring on a certain tooth there’s a small ticking noise each time this tooth hits the chain.
It may be a combination of issues.
If the front derailleur was fitted slightly too low would this cause issue with shifting down to the 34 tooth from 50 tooth ring?

wongataa

daviescgwen said:

If the front derailleur was fitted slightly too low would this cause issue with shifting down to the 34 tooth from 50 tooth ring?

Unlikely. If it was fitted too low it wouldn't clear the large chainring so you couldn't use it. Issues shifting between chainrings will generally be down to incorrect cable tension, incorrect end stops, or a mixture of both.

When I had a Shimano front derailleur in the past that kept dropping the chain during shifting I fixed it by setting it up from scratch following the Shimano instructions. It worked fine after that. The issue was something in the setup was wrong and by setting it up myself I knew it was set up correctly.

trevor.hall12

There are slightly bigger teeth on a chainring and it shouldn't touch ever the gap should be 1 to 3mm
So it does need moved if it touches but as said above it wouldn't make the chain drop on the inside

daviescgwen

I think I’ll follow the advice and set it up again from scratch.
Thanks everyone

imposter2.0

daviescgwen said:

I’ve had it checked with a bike mechanic as this was my first thought.

Not being difficult, but could said mechanic not have diagnosed the chain dropping issue at the same time..?

trevor.hall12

daviescgwen said:

I think I’ll follow the advice and set it up again from scratch.
Thanks everyone

There's a very specific way of setting up the 8000
This shows it perfectly
https://youtu.be/R67WQB9JkhA