The 5 arm spider of the FC-M739-5 has a BCD of 94/58mm whereas the 5 arm spider of the FC-M950-HG uses 110/74mm. Is it possible to use the XTR spider on the XT crank?

2 Answers 2


Yes, it's a fit with XT.*

You can't interchange with LX or STX-RC though because, even though the spline is the same, the spider is thicker (maybe the material is softer).

You can borrow my lockring tool if you like though I think it's the same as the ISIS BB tool.

*you might need to file the chainring arms slightly to clear the crankarm when using the XT spider on the XTR arms. XTR spider fits XT no issue.


Unless you are a super-capable machinist with incredible machinery, that's not possible. I'd say, practically impossible in this case.

If this is a life and death situation, I'd cut the old spider, fabricate a hollow disc that fits into this that is having 94/58 pattern, and bolt into the crank. This is a bit easier than machining a Hirsch joint, but still very, very hard even for an expert machinist.

I'd say machining a new crank from a block of aluminium is probably easier. Sorry.

  • 1
    FYI, I think it’s Hirth joint, not Hirsch
    – Weiwen Ng
    Jul 22, 2023 at 10:24

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