If I remember my Big S right, should be fine, and I think the DA one uses one grade better bearings. Don't quote me till I go ask.

 

That combo is fully compatible. All Shimano road external BB's share the same width / diameters and are interchangeable.

Despite what Shimano might say the only difference I've found with the different BB's is the colour of the cups.

 

Yep.

FSA and the drive side of SRAM, too, for whatever that's worth.

 

PBK has Ultegra BB in stock for $23.71. I ordered one last night along with a Ultegra groupset. Shipped out this morning.

BTW-I have a Phil Wood BB on my other bike. Bought it in August before the market crash when times were good. It's one sweet BB, so smooth and SS cups as well. I'll have one to replace the Ultegra BB when I can find an extra $100.

 

And you don't have to take our word for it. Here's the most recent Shimano drive-train compatibility chart:

 

Yeah, that's what I found, but didn't bother to scan / screenshot it in. Thx.

 

Thanks all!

 

per that chart you could use a fc 7800 crankset with the new 7900 bb .is that the way you guys read that?