Weight Weenies

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 fell 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?

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Not enough chain tension?

Does it happen without pedaling?

/a

Can you spin the bike in the small ring while on a work stand ok?

Shimano Ultegra Crank as well? Shimano chain... directional... printed side facing outward? Why did you put non Shimano rings on in the first place? Were they worn out? I doubt you will ever get “better” shifting by going with non manufacturers rings, or chain (SRAM may be an exception here). Is the chain in good condition, not worn.
There’s clearly enough tension since the chain is coming off when standing (don’t get much more tension than that). I’m assuming you mean you are pedaling while standing (uphill) and the shift has already happened. Adjustment of derailleur is probably not an issue since it is coming off well “after” the chain has established itself on the small ring, correct? If it’s coming off when you’re shifting from big to small, then yes, check adjustment of derailleur. If the crank is also Ultegra, then chainline should be ok, unless the rings are throwing it off. My guess it’s either the chain or the rings, or both. If you continue to have issues, switch back to the Shimano rings.

Spin the cranks in a stand while in the problematic gear combo and see if there is any wobble. Use the gap to the derailleur cage plates as a frame of reference.

If the chain is loose and/or the freehub is not coasting freely then the slack can spread to the upper portion of the chain between low cadence pedal strokes. If then you are on the either end of the cassette, the jerking of low cadence and slack chain can get it to fall off.

I'd just check that the freewheel mechanism is smooth and that you have enough chain tension in small+small cog/chainring, to begin with.

It's just a hunch. Maybe worth checking out...

/a

The only time the chain should be anywhere close to “loose” is in the small-small combo. I sure as hell hope he isn’t spending any time in small-small, let alone out of the saddle in it. Even then, the derailleur cage should be pulling out any slack in the chain unless it’s sized wrong.

I like Alcatraz's theory. If you're stomping up a hill in the little ring/big cog, the chainline is going to have it more inclined to come off on the inisde. If you get to a slow jerkey cadence, it's possible that could have helped it along. Might also check for chain stretch, a worn chain or teeth on the ring might cause issues as well. Last suggetion, maybe adjust your low stop on your FD or get a chain catcher.

I had a similar issue once with a TA inner ring. Everything was new, but when I put some serious power, the chain skipped very badly. The chainring was not wrapped, mounted in the correct direction and nothing special to see. Was bought online, so I went to a Lbs, mounted the exact same ring from their stock and problem solved. We compared both rings and they seemed to be identical. Mounting the "old" one back, and the skipp was back. Never understood what was the cause, but I binned a nearly new chainring !

Bent teeth? Could it be that certain chainrings and gear combinations are sensitive?

Delorre wrote: ↑

Mon May 07, 2018 8:31 pm

I had a similar issue once with a TA inner ring. Everything was new, but when I put some serious power, the chain skipped very badly. The chainring was not wrapped, mounted in the correct direction and nothing special to see. Was bought online, so I went to a Lbs, mounted the exact same ring from their stock and problem solved. We compared both rings and they seemed to be identical. Mounting the "old" one back, and the skipp was back. Never understood what was the cause, but I binned a nearly new chainring !

Was it limited to certain gears on the cassette? Maybe it's the same for the OP?

/a

Sorry, but this is a red herring. There's no reason why a chain should skip off a chainring in even the most extreme road bike chainline.

The only possible exception would be small-small combos where the chain is actually hitting the ramp/pin on the big ring and being lifted off the teeth, but that shouldn't throw the chain onto the BB unless there's a lot wrong with the derailleur set-up and no chain catcher.

So check chainline and alignment of the drivetrain?

Give the OP something to check. Sometimes you can find the issue by checking something else, just gotta be pointed in the right direction.

/a

alcatraz wrote: ↑

Mon May 07, 2018 11:15 pm

Bent teeth? Could it be that certain chainrings and gear combinations are sensitive?

Delorre wrote: ↑

Mon May 07, 2018 8:31 pm

I had a similar issue once with a TA inner ring. Everything was new, but when I put some serious power, the chain skipped very badly. The chainring was not wrapped, mounted in the correct direction and nothing special to see. Was bought online, so I went to a Lbs, mounted the exact same ring from their stock and problem solved. We compared both rings and they seemed to be identical. Mounting the "old" one back, and the skipp was back. Never understood what was the cause, but I binned a nearly new chainring !

Was it limited to certain gears on the cassette? Maybe it's the same for the OP?

/a

It had nothing to do with cog on the back. Regardless of gear, some serious power (and a few light bumps) were enough for skipping. In the big ring everything was fine, with a new inner ring also! To OP : try an other chainring to be sure

Praxis is known to drop chains from incorrect offset.

First you need to check to make sure the chain rings or the arms are not bent, which I'm sure you probably already did, so probably not the problem?

If that's not the issue, as mentioned above, then it could be the Praxis wave tech ring, I've heard that Wolftooth HG+ with a specific narrow wide profile ring works with those.

Also, the Praxis has a lot of issues when using a SRAM chain.

If your Praxis is new enough to have a warranty then contact Praxis, if they determine it's the offset, which is what I think is the cause, they will send you 3mm offset free.

froze wrote: ↑

Mon Apr 25, 2022 1:04 am

If that's not the issue, as mentioned above, then it could be the Praxis wave tech ring, I've heard that Wolftooth HG+ with a specific narrow wide profile ring works with those.

Also, the Praxis has a lot of issues when using a SRAM chain.

If your Praxis is new enough to have a warranty then contact Praxis, if they determine it's the offset, which is what I think is the cause, they will send you 3mm offset free.

Wave tech? Narrow-Wide? He has a 2x road chainring setup

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