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  1. #1
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    Possible to use a 40t cog with a RD m737?

    I saw an 8 speed 11-40t cassette for sale.. is it possible to use a 90s 8 speed RD with it? The max cog size for an RD M737 is like 32t. Maybe with a "goat link" or derailleur adapter? Do those lower the cage or push it back?

  2. #2
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    I recently bought one of those 8spd 11-40t cassettes. Many of the ebay listings also offer a knock off goat link thing, I've been assuming it's required to get it working.

    Somewhere I have one of those shadow derailleur goatlinks, will attempt using it with that. I think the shadow style goat link moves the whole thing down and back, the universal road style just moves it down.

    Edit: It appears the shadow goat link only works with 10spd derailleurs, likely have to get one those knock off mounts myself.

  3. #3
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    Have you installed yours yet? I did notice the listing has an option for a generic "road link" style adapter. I'm tempted to try it out but it seems like the long cage might end up being a little low. Maybe a shorter cage derailleur could be used instead

  4. #4
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    Have not installed it yet, was going to try a medium cage derailleur of some sort. Even with the 40t I don't think you need the chain wrap of a long cage.

    It's pretty easy to convert a XT 737 over to medium or short cage if you can find a donor. Shimano derailleur cages were cross compatible for like 20 years, anything XT or lower should work.

  5. #5
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    I actually found a mid-cage version of the m737 on one of my project bikes, so I swapped that onto the build I'm working on. I think with the shorter cage the RD won't be too low.. I'll probably try out the cassette with an adapter. I just wish someone made one that was a little lighter, and I kinda suspect they won't last long considering but the sunrace and sunshine ones i've seen are hi-ten steel

  6. #6
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    So I did end up trying out the sunrace 11-40t cassette with a derailleur extension, and it shifts through all the gears just fine.. but there are a few issues with the 40t gear and chainline: When in the 40t gear, the lower jockey wheel rubs against the side of the chain because of the chainline being so off. It's not a huge deal but it probably would wear out the jockey wheel quickly. The other issue is that when backpedaling, the chain derails off the 40t cog onto the one below.

    I'm hoping both of these issues can be sorted out by moving my chainring inboard more.. I've got a fair amount of clearance so I just ordered some chainring spacers. We'll see how it goes. But having 11-40 range is pretty sweet on an 8 speed! Just wish sunrace made a lighter cassette

  7. #7
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    I'm still waiting on some spacers to improve the chainline, but I put a 9 speed KMC chain which definitely improved the shifting when back pedaling. it didn't totally solve it, but it helped a lot. The 9 speed chain shifts just fine too with the 8 speed cassette and derailleur

    edit: moving the chain ring in 4mm helped with the noise and backpedal shifting. i could probably move it in more but I think it's good
    Last edited by frantik!; 3 Days Ago at 06:06 AM.

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