My current setup are using a full Shimano 105, medium cage GS 11-34t, crank are 50-34t. Through some digging, I want to upgrade the RD using Deore XT M8000 SGS Long, paired using wolftooth tanpan.

Based on tanpan product specification, it should work with 2 chainring setup with 11-42t sprocket. But I'm not sure. Is there anyone having experience doing this? Do I need change the crank to lower setup, a 46-30t?

  • I am looking at doing the same thing with GRX shifters. I have the tanpan and and XT RD-M8120-SGS. Did this work for you? Also, what cassette did you go with?
    – Sean
    Commented Sep 8, 2021 at 23:10

1 Answer 1


According to the Deore XT RD-M8000-SGS Long specs it should work (you are right at the limit though, but they are known to be conservative). No need to change the crank/chainrings (but you can if you want to).

  • yeah, based on the calculation it should be safe. probably gonna try it next week after I got the item.
    – gamalan
    Commented Sep 23, 2020 at 8:12
  • If you want to check a configuration outside the specifications, it's always worth a (gentle) try from which stepping back is easily possible. If the shifting doesn't work, don't force anything.
    – Carel
    Commented Sep 24, 2020 at 18:49

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