xtr m970 c/set to 2x9 set up

twonks

After my various posts on chainsets, cassettes and other things, I have more or less decided to go to a 2x9 setup with TA Chinook rings on a M970 xtr c/set. (Picked the crankset up yesterday)

The choice is 2 x 9 or just leave it as is and upgrade the rest to 9 sp.

I reckon the 26 and 38t chainrings with a 11 to 34 cassette will cover most of what I had when using 3x8 (11 to 32) apart from the very smallest or biggest gears.

Is it a simple conversion and will the rings up front be strong enough when mounted to the spider?

I ask this as I've read a few forum posts that say the larger ring is prone to bending as it is not supported as much as it would be normally, but am unsure how true this is.

I also think I'd need some 2mm spacers and new sets of ring bolts ?

And finally, what are the chances of selling the existing brand new Shimano rings?

They cost a fair bit as spare replacements, but not sure just how much call there would be for them,

Cheers.

nicklouse

it works you dont need anything else if you are running a bash.

cooldad

I have a bag of magic beans to swap for the rings.

twonks

Hia. Bet your getting fed up answering my drivetrain questions

I don't want a bash ring.

Am I right with the spacers thing on the small chainring, and what are your thoughts on the strength of the large middle ring compared with a std designed for the crankset smaller middle?

I'm quite a big fella and whilst not back to where I need to be and once was, putting 100kg of mass through bits of a weaker origin tends to upset them

nicklouse

I dont have any spacers on the small cog.

no bash yes you will need smaller bolts or spacers.

large middle ring is just the same a s a small big ring.

what was the question?

twonks

Thanks.

The question was 'Is the largest ring likely to be weaker than std' as I have read on a few forums that people are bending rings when mounted in such a fashion.

Something to do with the spider not supporting the rider weight and torque as well as it would do with a factory ring, but I have not read any more into it other than said forum posts.

If it isn't a problem then not an issue.

njee20

You do need 2mm spacers on the granny ring with M970s to compensate for the thicker ring. If you're not using a bash ring then yes short chainring bolts are needed.

It works well, I've run 28/40 on M970 cranks, and you can get good money for the stock rings.

You won't bend the outer ring.

twonks

njee20 wrote:

You do need 2mm spacers on the granny ring with M970s to compensate for the thicker ring. If you're not using a bash ring then yes short chainring bolts are needed.

It works well, I've run 28/40 on M970 cranks, and you can get good money for the stock rings.

You won't bend the outer ring.

Thanks, just what I was looking for

After looking at the ratio charts, I think 26/40 will give me the gearing I need to make it a worthwhile change.

Will a 2009 XT front shifter have the capacity to cope with this much differential on two rings?

edit. Had a look around and found pics and posts that suggest it will be ok.

njee20

Yeah it'll be fine, may not be the smoothest shift, but it'll work. It's about the front mech rather than the shifter anyway.

twonks

Jeez, this is getting tiring, but I only want to spend this much in one go once

Have now got thinking about maybe coming to 10sp which will give me the same low gear as I have now.

Looking at the FAQ suggests a 9sp Crankset will work with a 10sp chain, so I am now thinking of ending up with the below.

Chainset - M970 arms with TA 26/38 rings (Will this be ok with 10sp?)
Front Mech - XT 9sp
Rear mech - XT 10sp
Shifters - XT 10sp rear, front ?
Chain + Cassette 10sp XT 11-36

Only thing now is the rings compatability and the front shifter as I am not 100% sure if the 9 and 10 sp versions are the same, as I'll essentially have 9sp front and 10sp back?