Hopeless at this kind of thing, any ideas?

Also, can you use any length cage rear mech for 1×9?

Thanks

IIRC 113mm axle length is for correct chainline for middle ring. You may wish to go for outer mounted single ring in which case you need a shorter axle.

Cage is dependent mainly on cassette range. Short cage I believe wont like more than 11-28T so depends on your block.

I tend to use 118mm on my Inbred/Scandal for a bit more chainring clearance as its pretty minimal and I prefer to use a 36t inner and 26t granny but, as stoner says, it depends where you mount the single ring

It depend on your cranks a bit. Are the doubles or triples? Probably anything between 115 and 127mm should be fine.
A short cage rear mech should work fine with most cassettes on a 1 x 9 (i run a 32 x 11/32 with a short sram mech and its fine). You might struggle if it a cassette bigger than 34 though.

It depend on your cranks a bit.

^This, +/- a few mm if you want to mess with the chainline.

113×68 is standard so will be fine for 32t in the middle ring position.
Adjust from there if needed.

There is no “standard” bottom bracket. It’s a 68 mm shell, but the axle length will depend entirely on your cranks. I have two singlespeeds, one needs a 108mm , the other a 125mm as they are different cranks.

Anyone who tells you an axle length without knowing which crank you are using is just guessing.

What cranks are you using?

As above, the cranks determine what length axle you need. It is worth noting though that inbreds have fairly wide chainstays and it can be worth having a slightly wider one that is theoretically correct to get more clearance to avoid chainsuck eating the stays…

113mm is about as close as you’ll get to a ‘default’ option based on averages but you’d really need to check against your cranks.

Thanks for the replies, cranks are Truvativ Hussefelt

it’s 68mm shell. I’ve used 113 in the past but am running a 118 in my scandal at the moment and it seems fine