Roadie607

Does anyone know if the bearings in the new(ish) Shimano 6800, 9000, XTR, etc. bottom brackets are smaller than the previous generations? I recently got my hands on the Dura Ace BB9000 and noticed a profound difference in the size of the cups when compared to the DA 7900 BB it's replacing. There is a significant drop in weight in the newer design (110 g to 70 g IIRC) and the bearings are probably the heaviest part of those BBs, so it's hard to imagine losing close to 50 g from just seal redesign and more extensive machining of the cups.

Thanks

reptilezs

i believe they are smaller but shimano said the bbs last longer. the seals are a labyrinth seal as well as contact seal

reddog3

As long as they are the same ID, and fit the frame- doesn't much matter. However, I'd want to have both in hand and weight them myself. 40 gams is significant in what was originally a 110g part. Put their feet to the fire.

Roadie607

How would that not matter? Smaller bearings mean a shorter service life if I'm not mistaken. I'm really not interested in anything else when it comes to BBs. I installed the cups before I weighed them because I'm stupid and impatient but I do remember they felt noticeably lighter than the 7900 BB they replaced.

reptilezs

my experience is that dirt and water kills bbs not bearing size in particular

Barrettscv 

Smaller bearings mean a lower load capacity. Durability is the result of hardness and quality standards along with lubrication and contamination. Unless you are Andre Greipel, you not likely to approach the load capacity of a Shimano bottom bracket.

Roadie607

Gotcha. Well time will tell if the seal redesign worked, though I've always had good experiences with Shimano BBs (at least compared to GXP). Thanks for the input.