Loose Sensah SRX derailleur

[svanimpe]

Did anyone notice this?

https://share.icloud.com/photos/0Fi7iImS4OY8lIvAF4TGf6uKw

The derailleur (and the ring that contains the stoppers) moves freely, even after fully tightening the screw that attaches to the derailleur hanger. I'm hoping the chain tension will be enough to offset the cable pull, but it still looks weird.

[1Sigma]

If it is just freely pivoting at the hanger bolt, this is normal.
It is meant to pivot.
The tension from the chain will keep it taut.

This is not a Sensah thing either.  For example, my Shimano 105 RD does the same thing.

All good. Nothing to worry about

[dpitel]

Not to be mean, but posts like this really make me wonder how people manage to build bikes on this forum. Like, I would NOT have attempted building a frame with no knowledge of bike mechanics. TBH, I'm kind of jealous at how brave folks like that are- when I first got into cycling and then working on bikes- I was terrified of fucking something up, let alone undertaking such a massive project.

But, to answer your question, it's perfectly fine and that's the way those derailleurs hang until there's a chain and a cassette in the picture. You're good.

[svanimpe]

@dpitel: Yeah, you're being offensive here. I have plenty of experience building bikes from scratch, from vintage steel bikes, to fully integrated carbon bikes.

However, I've mostly used newer Shimano groupsets so far, and Shimano derailleurs do *not* rotate freely around the hanger bolt. In fact, their technical documentation specifically says that tabs on the derailleur and hanger should be aligned, and that there should not be a gap after tightening the derailleur hanger bolt. This Sensah derailleur is completely different, as the tabs rotate freely without tension from the cable and chain.

[jokage]

However, I've mostly used newer Shimano groupsets so far, and Shimano derailleurs do *not* rotate freely around the hanger bolt.

Really? https://youtu.be/OX3iDvrd9GY?t=140

[svanimpe]

@jokage: Look closer. That derailleur doesn't pivot around the hanger bolt, but around one of its internal bolts. The piece that attaches to the hanger (and has the stopper tabs) is fixed.

[1Sigma]

@jokage: Look closer. That derailleur doesn't pivot around the hanger bolt, but around one of its internal bolts. The piece that attaches to the hanger (and has the stopper tabs) is fixed.

Perhaps you could send a video of what you are referring to.
Would have been helpful if I watched the video first... 
That does look a little weird and I couldn't tell you if that is by design or not.

Send an email to sensahsmart@126.com.  See if they reply

Edit:. Watching the video again, I don't think there is an issue.
The b-screw assembly is the free moving part in question.
There is no lateral movement it seems, and otherwise the RD looks securely mounted.
Attach the chain, and play with the b-adjuster screw. If it still does its job of adjusting upper jockey wheel spacing, (which I suspect it will) then I would say you are fine.

[svanimpe]

Yeah the derailleur works fine once the cable and chain are installed, so I guess it's by design. Now I know