Do they exist for a Shimano XT crank?

I’m just scared of taking the cog off my Alfine hub and putting a bigger one on, taking off the snapring seems to involve a bit more grunt than I’m comfortable with.

not seen any, 30T is pretty small, it may not even fit as there won’t be much gap between the teeth and the bolts. Are you sure you want to go even lower on the gearing?

Anything with a BCD of 104mm should fit fine.

http://www.extralite.com/Products/octaramps_anglo.htm

Im considering one for an Alfine too. It’ll be outwith Shimanos recommended gearing but it’s for a Fatbike and I’d like to move the whole gear range down a bit.

There’s a little filing too be done to the crank arms. Nothing destructive.

Going to cross the Pyrenees with gear attached so a very low gear might be nice. I’ll probably just take it to the LBS and let them hack away at it.

The snap ring is a doddle, but if you are worried about breaking it buy a spare when you buy your sprocket, SJS sell sprockets up to 23 teeth ( they may be marked as sturmey archer but they all fit,the beauty of changing sprockets is that you can fit them in about 10 mins ( with practice) and you can change to higher gearing when the going gets flatter/downhill and there is minimal weight penalty for the smaller sprocket

Up to 25 tooth sprockets are available

I used the Extralite ones for a couple of years – as Druid said you have to file a 45 degree chamfer on the spider so the chain clears it. 10 minutes with a file did on my M970 and Lightning cranks, not a big issue. I’d not do it to Race Face cranks though – I suspect you’d be out of luck on a spider-based warranty claim if you’d butchered it!

They last pretty well for a lightweight ring. I had one break apart (literally – into 3 bits) when a bolt came loose, which was obviously my fault, and another one just wore out, but life was very acceptable.

Their chainring bolts are a little soft, I’ve had more luck with (alu) ones from eBay or the Brand X CRC ones.