M770 XT chainring question

[Fatal Swan]

Anyone know if the M770 XT chainset has to have the specific (outer) ring or whether others will do? I wanted to use this silver outer ring which is the right BCD (and gives the chainset a different all-silver look which I quite like), but installing it it looks like the ring os not thick enough (see photo) so I'm wondering whether the outer ring will then be spaced too close to the middle? Any experience of this?

Cheers

 

[ishaw]

I've just had a look at mine and the chain ring is straight from the outside, with the machining on the back taking up the space and making it flush with the front of the spider. My guess would be that you will be reducing the space between the outer and middle ring by a few mms.

You could just add some spacer washers behind the outer ring to make it flush, or even space out the middle and inner.

I read somewhere that if you replaced a ring on an xtr chainset of the same era, you needed to do all 3 due to the spacing of the rings being reduced if you did just one. Maybe the same is true here?

Do you have the full set of rings that match the new outer? Do you have the original outer ring as you could always measure the gap? It may just work but I suspect shimano knew what they were doing with the original rings and spacing but you never know....

 

[Fatal Swan]

Cheers. I suspect the alignment is going to be out too - it's a really big difference on the spider (something like 4-5mm). As it happens I came across a 770 outer ring on ebay yesterday that I snapped up (it was cheap - at least for an XT ring, since it wasn't advertised as such). So I'll be able to stick with the standard setup since the current inner and middle are also 770. Once I have the 770 outer ring I'll compare both and report back...