help with problem. centrelock sheared

What sheared? The thread in the hub or the lock ring?

new hub. I have had a similar issue when the thread sheared so the brake was useless and I do not ever wantto have to go through that again

(on a tandem when the front brake had already failed for an unrelated problem, where the thread that failed was a screw-on 6 bolt mount, on a fairly steep hill)

thread sheared on the hub.

bloody centrelock rubbish

Where have you put the cassette spacers such that the thread now engages? I'm just a bit confused.

disc back on splined part then 1 large, 1 paper cassette spacer then the lockring. 

How did that help

Any pics as can't visualise 

Surely a spacer would mean fewer threads engaged?

it's an alfine 11 hub so needs the spacers to clear the locknut

This sounds like a new hub.

Sorry.

Would you not use an external lockring?

Nope. Still don't understand (and I've had an Alfine 11 hub). 

the lockring is still intact but the top 2mm of the hub thread has sheared off.

i can put the disc on the splined but because of how it all fits together, usually it's lockring/spacer/rotor if i put the original spacer on there's not enough thread on the hub for the lockring to engage. what I've done is put 2 cassette spacers in place of the original spacer which then allows the lockring to bite the few remaining threads on the hub.

I've actually now, glued the rotor on, taken bike for a ride and I'm not dead...yet. I'll keep an eye on it but as the hub is ****ed anyway a bit of glue won't make it worse, can't really afford a new hub at the mo. 🙁

thanks for listening!

Is the spacer needed?  I don't remember one tho I no longer have an alfine

unfortunately yes

why is the spacer needed?  Can you try assembling it without?  You need a spline tool with deep splines - one of mine would not work but another would as it had deeper splines

Pics would help

A bit of research shows a spacer.  Weird

https://handsonbike.blogspot.com/2015/04/avanti-inc-3-shimano-rt81-ice-tech.html

A bit of research shows a spacer. Weird

Surely you'd need a deeper threaded locking if a space that thick is needed.

I think a deeper thread would bottom out on the lockring before it secured the rotor as the spacer is taking up the space between lock ring and rotor 

Should the be a longer lock ring to account for the spacer? Looking at TJ's link looks like one should be used.

Might be a long shot but would a bolted six bolt adapter help? If you can get a deep lock ring that will engage all the remaining threads the perhaps modify the adapter with some grub screws that tighten onto the spline (or even screw into a new hole in the side of the spline to provide mechanical retention).

Might be a long shot but would a bolted six bolt adapter help?

I've done this before, epoxy and a modified deep lockring to hold it all together. Did another couple of years before it came apart, by which time a new hub was within budget.

my next question would be, is there a variation in lockring depths? had a quick scout about but nothing leaping out at me.

Yes.
Don't think anyone actually lists one though, just some are a couple of mm longer than others.

How does the thread depth left compare with say the front wheel? That link from tj shows that you need the spacer as the splines are deeper. Do the lock ring threads go further in so they can be fully engaged? If so, carry on as you were, with a thinner spacer if needed.

The braking loads are all taken on the splines so the lockring does not have to be gorrilla tight I guess as its just stopping the disc moving laterally on the splines

the front lockring thread has the same depth.

I've gone with the 'breaking forces mainly through the spline so glue the bugger on' with an untightenede ring approach for now. 

thanks for your help folks.

can't believe a whole hub is for the bin for want of a 2mm piece of metal thread.