Options for going 1x9 with an XT M735 and MS thumpy?

[Frankengoose]

So I've tried to learn more about square tapper cranks and the specific bottom brackets they require, in order to get a single chainring in the front and a 9 speed cassette in the back. I believe 9speed with the M735 rear derailleur isn't the problem. And putting a 9s cassette on my 8s hup also is ok. If my SL-T09 thumpy won't work indexed, it will friction based.
What I can't find is what 1x cranks I could to use, if I want to keep my 110mm BB. I would like to use an old Shimano crank if possible, just because I would like to use 2nd hand parts.
This is for a short-commute bike and I want to keep it low budget, so no Zee conversions etc.
Can you help me out here?

 

[mattr]

Pretty much any shimano crankset with individual rings that is compatible with your bottom bracket will work as a 1x crank.
Just need to get the right ring to fit it.

(And your shifter will work as 9 speed indexed with the M735 rear mech.)

 

[jimo746]

Re:

104bcd 4-bolt and 110bcd 5-boltare probably the two most available sizes of narrow-wide chainrings.
Many/most of the Retro mtb chainsets are 110Bcd 5-bolt, so take your pick from one that will work with your bottom bracket.
My Mrs's Retro Kona Hahanna has a 4-bolt 104bcd chainset on it, so that was dead easy to convert to 1x.

Of course, if it's purely for a short tarmac commute then you can probably use any chainring, it doesn't need to be a narrow-wide one really, they mainly come in useful off-road to prevent chain drop on the rough terrain.

Don't forget you'll probably need some single-ring chainring bolts too ..

 

[Frankengoose]

Re:

I took a while to respond because I wanted to follow the advice you gave. Both of you state I should pick a crank that'll work with my BB.
Well, this is the difficult part for me. I found this page from SB https://www.sheldonbrown.com/bbsize.html#chainline and been reading up on chain lines. Right now I believe it would be easiest to look for a 68mm BB/crank combo for sale, cause this would eliminate some guesswork of finding out which spindle length the crank needs. And yeah I will need some single-ring chain bolts too

 

[Tootyred]

You might be tying yourself up in more knots than you need to.

As mattr says above, pretty much any chainset will do. There's no guesswork needed to find the correct bb as if you already have one, put the crank on it and if its not the right chainline, subtract/ add to the measurement from there. Then you know what you need.

You can always shunt the ring with spacers too, if needed.

I run 1x9 and dont use a narrow wide either, i found them to be little help. What did is the use of a rohloff chain device. Forget the plastic rubbish.....never had a chain come off since switching 2 years ago! If your on a budget, just fit an old front mech and adjust it ( without the cable) to where you need it!

Good luck with the conversion.

 

[Frankengoose]

Yeah, I tent to complicate things according to my significant other.
So, I just went for it. I gutted a too-small-for-me Pine Mountain with 90s White Industries cranks on it.
Both BB are 110mm, both cranks are 175, so this should work.
But the White has a 94bcd and the only narrow-wide chainring for this seems to be a WolftoothXSurly that costs a fortune.
So I ordered a regular one and hope with commuter use the chain won't jump off