Rear derailleur B screw issue

Bicycling
1

My son has an issue with his rear derailleur that I’ve never seen before. Hope someone here has seen it and has a solution to resolve. The bike is new (May), The derailleur is a Cues U4000 9sp. The B limit screw has somehow become bent and no longer will shift into lower gears. I replaced the screw. It worked great for a day but the new screw is now bent. It might be new derailleur territory but hopefully there is a resolution.

Here is a photo showing the bent b screw for reference.

IMG_0475
IMG_04752070×1664 386 KB

2

Good to know I’m not the only one finding new ways to break things.

I’m guessing it’s just a case of bad luck and the derailleur took a hard hit that made the B-limit screw deflect/bend out of the way of the hanger tab. I’ve punched a B-limit screw straight through the tab leaving a nice clean little trough through the metal, but I’ve never seen the screw bend like that. You might be able to bend it back a little bit, but you might be stuck threading it all the way out the back and trying to track down a replacement screw. Should be an M4x20mm sockethead.

3

I have no actual experience with it but Reddit gave me this old link:

If the bike was new this year, are you able to take it back to the shop you got it from? Shouldn’t be failing repeatedly at all especially after this short period.

If not can you put another one in and cycle it through the gears on a workstand to see if it’s being loaded at an angle rather than straight end-on? What size is the top sprocket?

Hope that’s of some use.

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I saw that Reddit link. Didn’t fully help. The cassette is 11-46 which shimano says is comparable with cues u4000. The first time it happened I asked my son if there was a knock of some sort to cause it. He is 13 and was noncommittal in his answer :grinning_face:. I cut out the old screw out, replaced it with a new one and it happened again. I asked if there was a knock and he said no knock for sure this time. The derailleur looks good and straight, after replacing the screw the first time it cycled through gears correctly. Maybe the shop is my next stop. Thanks for the replies.

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