Replacing the big ring on an XT m739 4 bolt Crankset

[Woz]

Markybeau, is it one of the same that just bought the M569 middle ring on Ebay?

 

[Markybeau]

Re:

Er. Yes

 

[Woz]

I'll rummage to see if there is a granny ring and throw it in with the delivery.

 

[Markybeau]

Re:

That's really decent of you Woz

 

[captaincowelly]

Re:

I have a NOS M739 big ring if that's what you're after?Drop me a pm if you like.

 

[MT62]

I noticed that these spiderless cranks have an unusual outer ring, with I suppose what substitutes for the spider, built into it.

I’ve got an STX-RC spiderless crankset, of similar age, that appears much more straightforward, bolt off / on, but the XT m739 seems complicated.

What have people done when it’s time to change the ring, and what have they replaced it with?

....I tend to think the whole lot goes on Ebay in most cases. There's a constant stream of these XT and LX cranks going for peanuts with worn rings. Still, an excellent crank. If somebody actually made a single chainring compatible with the fitting the prices would sky rocket and SS junkies would be over the moon. A kind-of cheap mans Middleburn UNO.

A have already seen someone cutting most of the outer ring off, leaving the holes for middle chainring there, and using a NW chainring attached to the four holes. Just something to consider, might be a cheap way to bring the cranks back to use. Haven't tried myself, but one day... As I also have the crankset with worn chainrings .)

 

[ishaw]

Re:

Here's the one I have. Teeth look OK but pics tell a thousand words.

 

[ishaw]

Re:

Is it just me, or could you actually convert the spider to a standard triple?

Cut the extended bits off that join to the fixed outer, neatlu of course. Then file a step into it to allow the outer ring. There is already extra meat on there to put the fixed outer ring in the right place, spaced from the middle, and there is even a handy guide line inside the bolt hole by the looks of it. Shoot me down, but it looks very possible to me.

 

[d8mok]

Re:

I’ve got these at £25 plus post if you want a donor pair or even just to use them instead

 

[FluffyChicken]

While I think this has been sorted, if you search the forums you'll find 4 and 5 arm spiders can be fitted to these, the 4 arm come from later cranks. I think a small amount of modding is needed for the 4arm. But that is normally for use with the XTR arms.

Or grind the top ring and use it as a bash guard, fit a larger middle ring and have a double setup.