Shimano BB Crank compatibility

[Oswald]

A couple of questions here

I have a BMC GF01 with a BB86 Ultegra bottem bracket.
Can I replace this with a BB91 Dura Ace bottem bracket? (Can get my hands on one at a good price)
Can I replace my Ultegra cranks with Dura Ace 7900 or 9000 using the BB86 Ultegra or BB91 Dura Ace bottem bracket?
Can I use a Dura Ace 9000 crankset with a Dura Ace 7900 group? So will the 10 speed KMC chain and DA 7900 front mech work with the 11 speed DA chainrings?
Is the crankset for a SM-BB7900 different then the crankset for a SM-BB86 Press Fit?

Thx

[btompkins0112]

1. Yes, BB86 and 91 are the same
2. Both
3. Yes, the 10-speed chain will function fine.
4. No, all Shimano Hollowtech II cranks have the same spindle diameter/length.

[Oswald]

Cool, thx !!

[Oswald]

If I buy a crankset online, is the Crank Arm Fixing Bolt included with it? I mean the big center bolt that attaches the left crank arm to the axle?
I may have found a buyer for my crankset, but am not sure if I should also give him the bolt. Don't want to end up buying a new crankset online and then having to place a new order for a bolt... Also, is there a difference between the Dura Ace 7900 and Ultegra 6800 bolts? I'm not talking about weight, just need to find out if they are interchangable.

Thx!

[MajorMantra]

Yes, it's included, there's no reason to separate the bolt from the crank. Note that it doesn't hold the left crank on, it exists ONLY as a bearing preload. The pinch bolts hold the left crank arm on.

Oh, and a shameless plug, I wrote a post answering your original question in some detail: http://thesetbackpost.com/mechanics/shi ... of-things/

[Oswald]

Thx