Chain fall off the inner ring while standing

[Basrij]

Hello all. I have Praxis works 110 bcd 52/36 10/11sp Cold Forged chainrings with a Shimano di2 ultegra shifting.
All the time when i am on the inner ring( whitout shifting) at a steep road and standing on my pedals my chain fall off to the frame site.
What can be the problem? The chainrings are mounted with the sign face the frame toward the frame.
Can someone help me with this problem?

[BikeAnon]

Frame flex?

What frame do you have? Can you fit a chain catcher?

[Basrij]

Ok thank you, i will try a chain catcher

[BikeAnon]

Was the derailleur installed by a professional? I little bit of angle in the wrong direction can be a bad thing.

Same with the limit screws. A little adjustment goes a long way.

[Squint]

Mine improved a lot but took months of tweaking. Chainline was wrong due to poor documentation. I still have an issue where the chain spontaneously drops from the big to small ring. Lengthening the chain helped but now it's probably too long. When my Shimano R9100-P powermeter arrives I'm done with Praxis.

[Basrij]

Was the derailleur installed by a professional? I little bit of angle in the wrong direction can be a bad thing.

Same with the limit screws. A little adjustment goes a long way.

The derailleur is installed by a professional. This has nothing to do with the derailleur.
Just pedalling without force on a flat road at the inner ring there is nothing wrong and without shifting at the same inner ring on a steep road ,standing, the chain fall off.

[Basrij]

Mine improved a lot but took months of tweaking. Chainline was wrong due to poor documentation. I still have an issue where the chain spontaneously drops from the big to small ring. Lengthening the chain helped but now it's probably too long. When my Shimano R9100-P powermeter arrives I'm done with Praxis.

I know it's frustrating.

[stormur]

Judging by drivetrain it's road bike (?). Majority of them are designed "for Shimano". It's really difficult to f___k so much chainline in roadbike frame to such issue occur from that reason.

My suspicion is chainring. Against all paid "opinions" here and there about Praxis, it's not as good as many readers think it is. So first point for inspection would be inner ring.

2nd weak point can be chain. recently I saw few ( to be gentle ) Shimano chains with bent links due to shifting under force. Loose link can cause such phenomenon. But it will affect also rear shifting noticeably.

RD has totally nothing to do with it. it's physically impossible to adjust it so wrong to cause such issue.

Frame flex- yep, it can be also that- specially if drop happend under low cadence + high wattage.

[Basrij]

Judging by drivetrain it's road bike (?). Majority of them are designed "for Shimano". It's really difficult to f___k so much chainline in roadbike frame to such issue occur from that reason.

My suspicion is chainring. Against all paid "opinions" here and there about Praxis, it's not as good as many readers think it is. So first point for inspection would be inner ring.

2nd weak point can be chain. recently I saw few ( to be gentle ) Shimano chains with bent links due to shifting under force. Loose link can cause such phenomenon. But it will affect also rear shifting noticeably.

RD has totally nothing to do with it. it's physically impossible to adjust it so wrong to cause such issue.

Frame flex- yep, it can be also that- specially if drop happend under low cadence + high wattage.

Thanks for your reaction.
I also thought there's a issue with the inner chainring. I think i'am gonna replace it and look what it will bring me.

[wheelsONfire]

What bike do you have?
I had this problem also, but on my bike it actually proved to be the chainline.
I had a standard 6800 crank on my Open UP. Chainline is 43.5mm.
I suspected it was chainline after i had been tweaking the rest.
So i ordered Easton EC90SL crank and axle, a special CNC milled spider from Kent Eriksen and Wickwerks chainrings.
Now with the new spider, i have 46-47mm chainline (standard Easton 2*11 chainrings is 45mm).
Anyway, now the chain never drops at the small chainring.

Most say the 12*142 bikes have cassette spacing same as 135 dropout bikes.
So it should work just aswell with a standard 43.5mm chainline crankset.
But for me it is obvious , the wider chainline solved the issue on my bike.

Chain is same and chain length is also same using either Shimano 6800 crank or Easton/ Kent Eriksen crank.
Cassettes used in my case, Shimano UL 8000, 11-34 and Sram PG-1170, 11-36.
Chain is latest Shimano HG-901.