My Shimano rear derailleur was destroyed, for some reason got into the rear wheel, so I had to buy a new one. Hanger was a little misaligned but I think I fixed it.

I bought the new derailleur, changed cable and housing, the chain was pretty new.

All installed, checked L and H, and I noticed the derailleur was a little close to the cogs. but worked fine in all the 6 smaller cogs.

When I try to go into the biggest cog, no matter the B screw, the sprocket is touching the cogs (with the chain in between) making a weird noise and sometimes it cannot even get up there.

The first derailleur was a Shimano TY500 6-7 speed. I ordered another one, a Shimano Tourney RD-TY300 6/7-Speed but is doing the same thing!

The rear cassette has a biggest cog of 34T

I'm running out of options... only I can think is replacing the hanger to see if that is the issue. rear cassette

rear derailleur

  • 1
    Show some pics please. May 18, 2020 at 0:30
  • 1
    Closeups of the the B screw showing the hanger might help.
    – mattnz
    May 18, 2020 at 0:40
  • 2
    By "sprocket" do you mean the jockey wheel? May 18, 2020 at 1:59
  • a) the derailleur should pivot freely around the bolt that attaches it to the hanger - does it in your case? b) it may happen that the chain is a bit too long and does not move the cage "counterclockwise enough" - try to move the cage by hand like you would like to loosen the chain. c) if all fails, hanger extender (enough listings on ebay) can be a solution.
    – Mike
    May 19, 2020 at 11:45

1 Answer 1


Both the TY-300 and TY-500 are rated for a large/low sprocket of 28T to 34T so they are both within spec. There are no other variants, only the -SGS long cage is available.



I'd strongly suggest checking the the hanger alignment before spending more money on replacement parts.

You need a bolt that fits the hanger (possibly salvage this from your old destroyed unit) and a longish flat rigid bar, and something to measure down to the rim.

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The measurement of the offset to the rim needs to be as accurate as you can, but within 10mm at the rim should be adequate.

The other option is that your B screw is damaged, bent, not pushing hard enough, or the stop is broken/damaged/missing. A clear and well-lit photo of your frame and hanger would help show if this is the problem.

  • 2
    I didn't think about the hanger being bent - would also explain why the orginal derailuer " got into the rear wheel,", so its likely to happen again unless the hander is straightened.
    – mattnz
    May 18, 2020 at 5:15
  • 1
    The stop for the B screw may be broken or bent so that the B screw doesn't even touch the stop.
    – Carel
    May 18, 2020 at 7:19
  • Hi! thanks for all the answers! the B screw should be ok as i tried with 2 new derailleurs. with sprocket I was trying to say the jockey wheel :) I think the alignment of the hanger is the issue. will check that further! Sorry for an additional question... how do i post a picture? May 19, 2020 at 1:04
  • @LucasMartinez the B screw stop may be damaged - that's the part of the frame or hanger where the B screw presses. You can add a photo to your question using the edit link
    – Criggie
    May 19, 2020 at 8:24
  • 1
    It was the hanger alignment! Thanks @Criggie now it's working beautifully! May 20, 2020 at 13:19

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