12 speed woes!

[Chris]

Hi all,

Can someone advise me please!

I've just converted from 11speed xt to 12speed xt/xtr mix running a 32 front ring.

I nievly assumed I could run the existing front ring as a temporary fix as it's fairly low mileage.
I've since learned that it won't work and need to get a 12 speed compatible option.

My question is, will it work by just throwing on a new compatible ring onto the 4 bolt xt M8000-b crank designed for a double ring or do I need a single specific crank set?
Is there an offset difference to allow for the wide gearing?

Thanks in advance!
Chris

[jameso]

2x11 to 1x12 on the same crank, right? You need to get the right chainline for the 1x12 rear. M8000-B, so you have 148mm with rear end? M8000-B for 2 rings has a nominal chainline spec of 51.8mm, inner ring at 45.8mm and outer at 53.2mm. Boost or standard 12s Shimano 1x chainsets have a CL of 48.9mm.

So your new ring on the outer position will be 4.3mm further out vs ideal spec, about a sprocket's worth which might mean it doesn't run quite as smoothly in low gears or is more prone to chain drop if you back pedal in bottom gear but the chainstay length can make a difference (longer the stays the less difference that 4.3mm makes). Not ideal but may be workable esp if you're not using the lowest gear that often.

[Chris]

Thanks for the detailed info.
Yes it's running 148 rear end. It's a stooge scrambler
I was previously running it as 1x11 on these cranks without the smaller ring fitted.

In the dry fit it felt like there was a lot of pressure on the chain line when it the big 51t.
I've ordered a cheap ring just to get it running but it sounds like a new crank might be the way forward.

Cheers
Chris

[jameso]

You might be able to get an offset chainring? idk, I think they're designed to offset outwards rather than inwards and haven't tried flipping one.

[Chris]

Good shout!

Thanks