XT M770 chainset. The drive side bearing cup died on the way home last night. Not knowing any better I rode home, about 10 miles, taking it a bit easier than normal though.
Inner race has split. Apparently the loose BBs have ground their way into the axle leaving three very distinct grooves.
So would you ride on it? What's the risk of it snapping?!
nice:
inside:
Advantage square taper.
i'd still run it but guess it has weakened it some what, especiallly to heavy landings
The 2 grooves on the right of the first photo look very deep, so no I wouldn't risk it...
blimey !
what happened to the plastic top-hat thingy ?
(no, I wouldn't ride it - not hard anyway)
That doesnt look like 10 miles of easy pedalling it looks like the bearing has been shot for a while. I wouldnt ride on it, a bust crank axle isnt something you can cobble together with a zip tie
New cranks time 
That bearing must have been effed for a long time (the axle can still spin in the bearing even if the bearing is seized. And as mentioned above, where was the plastic protector sleeve, or what is a crappy after market BB?
Either way, the crankset is scrap.
Yip a new chainset is the answer to your question:)
@ scaredypants: The plastic top hat thingy wore through. The hat bit was still on the axle, the other half stayed in the cup when I removed it.
@ pantsonfire: Just refitted the cranks, no previous damage, bearings were ok.
I could tell something was up when it happened, started clicking and developed play. Imagine that the 'top hat' just disappeared, that much play. I am now kicking my self for not stopping. If it was square taper or octalink this would not have happened!!
Can you still buy crank arms individually? not listed on Madison's website.
anyone remember the superstar bb that snapped the xtr cranks. think i'd have cried.
maybe someone should start making brass top hats ?
Top hat, or what is left of it. The outer surface is facing the desk. You can kinda see the ridge where the bb's have worn through the plastic.
I would not ride that!
You can get single arms, but since the rrp is up around 200 i would just get a new set from merlin for 120(as i would imagine the arm alone would be around this price).
Official: it is pissed as a fart.
The axle is actually bent, the grooves have stretched the material out.
Consequently the outer chainring has 4mm side to side movement per revolution.
thanks for the advice peeps.
New crankset it is then, I don't need the rings so hopefully might be able to make some money back 
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