Need help choosing components

[speshboy]

I am looking to upgrade my cassette and chain rings but before I order them, I would like to be sure that they will fit. My current components are:

Shimano HG-50, 9-speed, 11-34t
CRANKSET shimano FC-M442-8, Octalink Spline, replaceable rings w/ alloy outer
chainrings 22S x 32S x 44A

I was looking to buy the shimano xt M770 9 speed cassette and Shimano xt m770 inner and middle chainrings. Would these two components be a direct swap for what I have now? Are all 4 bolt chainrings a standard sizing or do the position of the bolt holes differ depending on the cranks?

Thank for any help

 

[willsy01]

Yep, they'll be fine. Both cranksets are 4 x 104mmPCD for the middle and outer rings.

 

[speshboy]

So it's ok for the inner ring too?

 

[PerthMTB]

Yep, they'll be fine. Both cranksets are 4 x 104mmPCD for the middle and outer rings.

Not so fast...

Shimano have been 'experimenting' with their middle chainrings over the last couple of years, and although the BCD remains the same, thats not the only thing that determines if a chainring will fit a crank spider.

Specifically for what the OP wants to do, the M770 middle is a 'composite' chainring - steel teeth encapsulated in plastic. Yes the bolt holes are in the same place as steel and ally middle rings, but there is more material below the bolt hole, the black plastic bits below the holes in this photo :-



What this means in practice is that if you try and fit an M770 middle ring on your cranks, you will need to either file a bit off the chainring under each of the bolt holes, or file off the tab on the crank spider arms that the chainring sits on.

Don't let this put you off though, as the composite chainrings are great - wear well, quiet in operation, and shift smoothly. I fitted one to a set of deore cranks and chose to file the tabs off the crank spider once, rather than file the chainring down each time I replaced it. But if you go that way, there's no turning back so be sure you're gonna stick with the composite rings!

Outer and granny rings don't have this problem, and are cross compatible.

 

[pharmaboy]

inner is 64 4 bolt pattern

edit re above - yes, the year of the crank arms decides whether it seems to fit, but wont quite change correctly, or fits dead on perfect - had that problem a couple of years ago, and still have the composite in its packet waiting for some bike sometime to wear out a middle ring (main bike is 10sp now, so uses different rings)

 

[speshboy]

Thanks for that guys. Looks like the inner should be a direct swap at least. Just having a look at CRC again there seem to be 2 or 3 different models of XT rings. Anyone know the difference? Maybe some are the composite ones?

Another question, I probably need to get new rotors for my Avid juicy 3. Is it ok to run the G3 rotors instead of the G2?

 

[PerthMTB]

Just having a look at CRC again there seem to be 2 or 3 different models of XT rings. Anyone know the difference? Maybe some are the composite ones?

The older XT middle rings (eg M750/760) are plain alloy, and should fit your cranks without modification. The newer ones (M770) are steel/plastic composite, and will need you to get the file out as above. There are also 10-speed ones (M770-10 and M780), double specific ones (M785), and 36T ones (M761) - avoid.