Weight Weenies

hi just building a bmc impec with di2 6770 10 speed,with the frame being bb30 obviously have to use an alternative crankset(yes I know about the convertors but bb30 is installed).ive been told and after research would seem true that an 11 speed fsa slk light will work with the 10 speed cassette using a 10 speed chain,question being thou which I cant seem to find an answer to is will the 6770 10 speed front mech be compatable??

So, the question is whether an 11 speed crank and chain rings will work with a 10 speed drive train. The answer is yes. In fact, I challenge anyone to do a blind test and tell whether they are using 10 or 11 speed chain rings. I have yet to see conclusive measurements that differentiate 10 speed cranks and rings from 11 speed cranks and rings. The manufacturers keep talking about this, but there have never been any measurements published, nor have there been users who have noticed a difference from my research. For example, praxis says that their rings are compatible with 10 and 11 speeds, even though no change has been made to the rings. And from my experience they shift great.

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No reason why the 6770 front mech won't work with your setup either. No difference between "11-speed" and "10-speed" front mechs. I use the 11-speed front mech with my 10-speed drivetrain.

As for the BB - Rotor make a very nice BB30-BB24 BB. The two halves screw together into the BB shell to keep it tight: http://www.rotoruk.co.uk/btmbrackets/convertors.php

I use it on all my BB30 frames to run my 24mm cranks.

thx for that,the only difference between the 10 speed and 11 speed rings that I can find are that the 11 speed chain rings are ever so slightly thinner

Well.....have you actually tried measuring them? Because I can't find a difference, and since the inner dimension on the chains is the same for 10 and 11 speed, and actually its the outer dimension that changes, I don't understand why they would make them thinner. But yes, that's what they say.....

I would just use the wheels mfg style BB converters and a Shimano crankset. I have a 6800 crank on my 10 speed Di2 setup, with that very conversion. It works perfectly.

My road bike has an 11 speed Di2 setup with a 9000 crankset and the wheels mfg adapters in the BB30 BB. It also works perfectly.

The shift quality of the shimano cranks/rings is worth it

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If you are lucky enough to have a non creaking bb30 shell and bb I wouldn't mess with it too much. Any 10/11 speed crankset will work with the chain.