Originally Posted by
dddd
What Campy recommended for this crank is dependent on the fact that this crank was designed specifically for a 130mm dropout spacing.
What frame is this? What is the dropout spacing?
Whether a particular bb length is ideal for a particular crank/bike setup actually depends on a lot of things.
The bb specifically designed for this crankset is conservatively long, for use with a great majority of bike's chainstay configuration and seat tube diameter, but is not necessarily the best choice for you and your bike.
I would first try for something that is effectively a little shorter, but in my case I have parts here to test out in a matter of minutes, so I can guess and then confirm at no cost.
I do this all the time, but I don't "worry" about it or stay up nights "thinking" about it.
Sometimes the outcome is marginal, and I can either true the crank so that there is a good couple of mm clearance all the way around the crank's rotation, Or I can pull the bb and install a spacer. Either way, it gets done, and the final test is whether the front derailer than has enough "authority" to pull the chain down to the granny ring while under pedaling forces.
I test-ride a lot of road bikes with triple chainsets, and am often dismayed by what seems like excessive chainline on many of them.
Unfortunately, today's cranksets with integrated bb spindles don't allow for any tinkering with the chainline measurement.
Some setups have such severe chainline that running the big-to-big has the chain trying to derail itself with nothing but the front derailer pushing it back up.
Not gonna have that on my bikes, but it should be said that I'm not a tourist and so won't need to make much use of the smaller rings with many of the smaller cogs.
Like I said, I think this Record symmetric bb is great because it potentially allows the owner to choose how they want the chainline to play with any chosen frame spacing, cog stack width and riding style.
I'm sorry there has been some confusion about my bike and my question. I guess I was not sufficiently clear. My question is not, "what BB do I need, or what is the procedure for optimizing a BB?" It was as I stated in post
#1 : Does anyone here know the difference in quantitative terms between the symmetric Track or Pista BB and the Asymmetric one, and can share measurements?
My frame is (again) a Terraferma, a US made custom. It is designed for a 130mm spacing. It has a 68 mm BB shell, English threaded. Except for possible over width across the outer edges of the chain stays, its details are quite similar to those of my Mondonico, a classic Italian design. The Campy Record triple I installed in my Mondonico uses this same Campy Record 111 mm Asymmetric. It has correct chainline per Campy spec, and balanced Q left to right. It is a joy to ride in part because of its symmetry.
Again, I'm not asking for instructions on hand-fitting and optimizing for this frame - sorry, not what I asked! And I have done so several times for this frame, already.
You say the BB designed for this crankset is "conservatively long" - what do you mean and why do you say that? Have you ever installed one with the crank recommended for it? Or do you perhaps have the dimensions for it, including left to right offset? If so, then that is the information I am looking for. My experience is that it is an excellent fit for a road machine with standard dimensions.
I'm glad you don't worry and you get things done. I hope you don't think I've accused you of incompetence.