Can dropout break due to a faulty cassette or a bad installation? Backstory: I currently have a BH Ultralight RC road bike that I use to ride to work. About 6 weeks ago I took it to the bike shop because the pedal was slipping over the cassette when I took off, so they changed the rear cassette and the chain, and they did a few other things. It cost $220, but The bike was running very smoothly.
Then about a week the dropout (that's what they called it) literally snapped and the rear derailleur got stuck in the rim. I took it to the shop again, they straightened the &quot;transmission&quot; (what they said), they also straightened and reused the chain, they changed the spoke and they installed a dropout. I picked it up and took it home.
The issue is that I rode it yesterday for the first and the ride is terrible: the pedal's slipping again, the chain is always scraping something regardless of the shift, and it's making all kinds of noises. It's just terrible.
Since they said that the cassette and the chain was damaged from the dropout break, I'm almost sure that they'll want to change the rear cassette and the chain once again. My concern is that the dropout has never snapped like it did before (I didn't even know that existed), and I'm thinking that it broke because they didn't install something right the first time I took it.
Question: is it possible that the dropout broke because something wasn't done correctly when the new cassette was installed?
It is possible that the rear derailleur low limit screw was misadjusted such that holding the shifter down allowed the RD to get snagged by a spoke. That is a fairly common cause of what happened.
Another possibility, also common, is the hanger (what you are calling the dropout) got bent inward for whatever reason, usually uncareful handling of the bike or crashing, after it left the shop, and the RD was able to get snagged that way
Unless something like a stick or vertebrate got caught in the wheel while riding and was able to reach over and snag the derailleur that way, it's likely one of those two scenarios. If you knew what click the shifter was on when it happened, that would be a clue.
It would be weird if the derailleur was unscathed enough to not need replacing completely. They're unobtainable for shops in a lot of cases right now, so that could be a factor that led to some kind of decision to de-mangle rather than replace it, which is idiotic in normal times but can now legitimately constitute good customer service. If this is what's happened, it could be causing the current bad performance and noises, as they usually wind up too misaligned and sloppy to work great. It's also of course possible they just did a bad job.