Replacing the big ring on an XT m739 4 bolt Crankset

[Markybeau]

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?

 

[daugs]

Re:

If you turn it over you will see a nut that holds the ring onto the crank. Before undoing the nut there is a wire clip that needs to be removed first. There is a special tool for the nut, although if not too tight there are some "alternatives" involving a hammer, bear in mind the nut is alloy.

As to replacement, you can either buy a replacement chainring on a like for like basis, the m579 set has same arrangement.

There is also a 5 arm spider that was available (I have on my DEAN) and converts crank to a five arm arrangement.

 

[marc two tone]

Re:

Pretty sure an isis tool fits, same for LX

 

[ishaw]

Re:

Don't cheap out on the removal tool. Do it right as if you mess it up, you will need a new lock ring too.

As above re. rings. Lx or xt replacement, or find a compatible spider that allows you to replace just the rings in future.

 

[Markybeau]

Re:

That bit I get. It's finding the rings...

 

[Woz]

Pretty sure it's the LX M569 outer ring (several on the bay) would correspond to your XT M739 - think daugs made a typo.

 

[Woz]

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.

 

[daugs]

Pretty sure it's the LX M569 outer ring (several on the bay) would correspond to your XT M739 - think daugs made a typo.

yes :facepalm:

 

[ishaw]

Re:

Just remembered I have a spare lx crank arm and ring. Iirc the ring isn't in bad shape. I can dig it out if you are interested.

The spline pattern for the ring (or spider) is the same as xtr m95x, but not sure if they would fit directly due to the extra tabs on the crank arm that fit into the correct ring/spider.

I just sold a set if xt cranks with the 5 arm spider, I'd check and confirm otherwise, as I have 94 and 104 bcd spiders for m95x xtr cranks.

 

[Markybeau]

Re:

I'd definitely be interested.