Can my XT M770 Crankset be changed to run 1×9 without modifying it? if so what do i need apart from a chainguide? (and any suggestions for one would be appreciated)

I've ran mine with a boxguide before with no modification, however, I needed to mod the guide as the tabs for the granny ring bashed the guide. I needed to swap the bolts for countersunk ones, and drill the area they bed into slightly further down so that they sat deeper in the guide and were flush!

I think we almost need a sticky on 1×9 – it's a popular topic!

Chainguides – popular choices include:

MRP 1.x
e.thirteen XCX
Paul's chainkeeper
Front mech with the limit screws maxed out (bit hit or miss IME)
That new 'widget' thing advertised aboot the place

Otherwise no modification needed, but it will work slightly better if you shorten your chain to the correct length.

What about a Single Speed designed front chainring ?
Do they not have taller teeth ?
Might prevent the chain coming off. I've run mine 1×9, & it only dropped the chain once, on a very rough corner.

I run a Blackspire DH chainring thinking I could get away with no chain device, dropped it once and once was enough. Had no idea, went to put some power down to clear a table top, cue an unplanned scrotum to stem interface.

That convinced me to get one, had a Superstar Components Laser one fitted at the weekend. For the money it seems pretty damn good so far. Quiet, functional, looks pretty good & cheap. Even comes with a BB adapter if you don't have ISCG tabs.

I just did this XT with an LG1, just had to get some Single chainring bolts!

I think we almost need a sticky on 1×9 – it's a popular topic!

yep – almost up there with what tyre fo….

Just use your current middle chain ring and fit an N-gear jump stop and bashguard.

tidier, lighter, cheaper.

http://www.gvtc.com/~ngear/
http://www.bbgbashguard.com/

I have a bashring fittted already (titanium from the classifieds – it looks superb in case anyone is thinking of one)

like the look of the N-gear jump stop, alternatively would an MRP 1.x fit with the bash guard fitted, or does that make it too wide?

I think you might have problems using an MRP 1.X or e.thirteen XCX with a bashguard, i.e. it might be impossible.