I broke my 2nd derailleur! what am I doing wrong?
 

https://cimg9.ibsrv.net/gimg/bikefor...f349f78af0.jpg

I've "winged" my way through adjusting it as I did originally when I broke the first one, so I'm still trying to figure out how it all works. I'm assuming I did something wrong though. IDK, you tell me. Somehow it ends up between the spokes. I was having to assist the shifting on my way home due to it suddenly falling out of position, the front derailleur actually, then I feel the bike eating the chain under me then see the pic above. Granted this time my bike was under a weird load as I had a trailer behind me with too much stuff strapped to it and the basket behind my bike. Not sure how relevant those details.

Would this derailleur work as a replacement? I will study the rear derailleur video I watched once before ride any of my bikes.
https://bike.shimano.com/en-EU/produ...TZ31-A-GS.html

Three questions - 1) have you had the alignment of the derailleur hanger checked? (All bike shops have a simple tool that measures whether your derailleur is sitting true/vertical/parallel to your frame or how far off it is.) 2) Is your chain long enough to run over the big cog and big chainring? If not, any chance you tried to get into this "forbidden" gear? 3) (Closely relateed to 2) Does your derailleur have a long enough cage to allow the big-big combo?

All three of these can do what you've seen. The second two cause 1) often.

It appears you multiple issues. Your front gear not holding. Your derailleur hanger was bent and not realigned correctly. Your derailleur was not set correctly.

No, do not bother with that derailleur.

Just saw something like this last night watching the Liege Bastogne Liege race. Mechanic hanging out the window trying to adjust a electronic derailleur for a rider. Showed him doing it twice, finally they showed the rider freewheeling with the derailleur ripped off the frame. My take: Derailleur wasn’t properly affixed or tourqed to frame causing mis shifts.

That replacement derailleur definitely won't work--wrong mounting to start with.

It looks like you're going to need professional help and tools on this one. Get the hanger checked and straightened, possibly even replaced if it breaks while straightening. The cassette will need to be removed to replace the spoke protector. As mentioned above, chain length and compatibility of derailleur should be carefully checked too.

Judging from the condition of the spoke protector, the low limit adjustment may be way too loose, the hanger is badly bent, and you shifted into the spokes.

Normally I'd remove the spoke protector, but this may be a good bike to have one.

If that spoke protector was in the same condition when you replaced the derailleur the first time, it should have been replaced or removed. If the derailleur were to touch it in its present condition, it would likely rip another derailleur off

You mention having a load on the bike (trailer). How is your spoke tension? Do you have flex in the wheel?

No, to the eye it looked good and I just made sure at it max inward range it wouldn't hit the spokes.

No, I've used the largest cog

I suspected in my previous thread related to this my derailleur couldn't accommodate all gears having issues with it. And I assume the previous derailleur that broke the same was stock. But maybe not. I just picked it up free, looked stock and used.

What's wrong with it? How do I choose one?

And anyone have any tips on bending the dropout back? I've hoisted up a bench vice one a stool and maneuvered on but what a PITA.

So what caused it to hit the wheel? Did I up shift past 1st? I wish I remembered at the time. I wonder if both incidents were only similar in end result but not cause.

So issues up front could have caused this too?

I just plan on fixing this all myself since I got my stand and I want to make sure I never do it again. On a budget. Is this derailleur hanger alignment tool necessary?

And how do you choose a new derailleur. I'll buy used so long as it's in good condition and suitable
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An improperly setup or adjusted rear derailleur can cause this, or a chain that is too short, or a bent hanger

But one other cause that hasn’t been mentioned is forcing a shift, especially to a larger cog while pedaling under load.

If you find yourself in the wrong gear trying to get up a hill and just force the chain over things get tweaked, chains can start separating, and before you know it the derailleur is in pieces or in the spokes.

I don’t know if this happened, but if you were able to shift the chain unto the largest cog without any issues when you installed the new derailleur, it might be your shifting technique; or shifting technique with other setup issues.

John

In general:
Improper installation/adjustment
Incorrect hanger alignment
Shifting under hard load and forcing the shift...when the springs recoil from attempting to shift under a heavy load they over shift usually between the largest gear and spokes

The fix: Bring it to a shop and let someone who knows what they are doing repair it

:) have you looked on YouTube? RJ has a number of good videos, he has some hack methods if you don't have the right tools.

Whats going on up front probably has nothing to do with the rear.

Seeing the fresh looking scratches on the seat stay end, just above the weld to the drop out, makes me think the der cage got tangled in the spokes of the spinning wheel. This rotates the der back and then up with so much force the der gets bent and often the spokes/wheel also suffer.

As others have said poor limit screw adjustment, bent hanger can both contribute to this possibility. Getting a stick caught up in the rear wheel spokes can also grab the der cage.

One poor limit adjusting method that I see too often (just yesterday at work on a carbon Trek with SRAM Rivel as example) is the mechanic uses the lever only to move the der through the gear range and relies on how much they see the der move as their feedback for proper limit screw use. BUT as most all current rear shifters are limited in their travel/cable pull (being indexed) the shifter has it's own range of travel that is only enough for the number of cogs it's made for. But the der is stupid and can't tell the difference between the shifter/cable moving it and some other object/force moving it. One really should use their fingers to move the der at it's limits after the initial adjustments just to make sure it is the screw that stops the der from getting too far into the spokes and not the shifter's limits controlling this. Yesterday's Trek service had me turning the limit screws nearly a turn each to establish the der movement range. This on a many thousand $ bike bought from a LBS (not ours and that shop just became a Trek Concept Store...) Andy

This is exactly how it's done--you should manually try to force the rear derailleur into the spokes when it's on the stand. Don't use the shifters. You will immediately see whether or not the limit screw is adjusted properly, while rotating the wheel at very slow speed.

Cool, I'll give him a look.

Thanks. I gotta study up on the park tools video I saw on adjustment. It's a bit of a process to get familiar with

Thanks for all the helpful responses. I'll update after studying and getting a new derailleur

Can't you see?? It's destroyed. I doubt you could ever get it back to spec. It looks mangled. Save it for spare parts--jockey wheels, springs, screws, etc.

Assuming it worked before, you could just replace it with the same model.

Please don't tell me you tried to adjust the dropout by lifting the frame up and putting the dropout in a vice. :eek:

How else would I do it?? I don't a pair of 30lb pliers. Is there a special tool or method for this? It'd be a shame to have to trash the whole bike for this little part

Check the RJ videos he's got a couple of ways to align the hanger.

It's essential if you plan on working on your own bike that you have a decent stand. There are several available, some fairly inexpensive.

If I didn't have the proper tools, I would use a large adjustable wrench (i.e., a Crescent wrench). You should be able to get a pretty good vertical and horizontal alignment with that. STAY AWAY FROM PLIERS!--especially the "30 lb" version.

You can get a derailleur hanger alignment tool for probably the same cost as a good adjustable wrench:

Hanger Alignment Tool

This one will definitely get the job done--and as for as many derailleurs as you seem to be going through, may be a good investment. The fact that it threads in makes it better than an adjustable wrench right off the bat.

And for the love of god, keep that bench vice away from that poor bike frame.

I personally just pay the shop $15-20 to align a hanger rather than buy the $85 tool for the rare times I've needed it done.
I have done it on POS bikes with a longer M10 X 1.0 bolt or a crescent wrench

Think it was suggested last go around that you were in over your head. This seems to confirm it. If you want to have a reliable bike you need to find a good shop.