Last May, I posted a one-year review of Shimano’s Dura-Ace SM-BB7900 bottom bracket. Since then, that original bottom bracket has accumulated an additional 2500-3000 miles. It’s been ridden in rain and snow, and seen plenty of hard, off-pavement use. And just like the previous twelve months, I employed a maintenance program that basically amounted to complete and utter neglect.
Eventually, curiosity got the best of me, and I decided to check the bottom bracket’s seals and bearings. Pulling the Vaya’s cranks revealed very little dirt on the external seals (and no uneven wear patterns). After a quick wipe-down, I checked the bearings for signs of play or roughness. To my amazement, I wasn’t able to detect any indication that dirt or water had infiltrated either bearing. By contrast, a comparably priced external bottom bracket from another company became contaminated by water and dirt (and was devoid of lube) in ten months and less than 1000 miles of use.
If my original Dura-Ace bottom bracket lasts another year, it will have cost me just under $1 per-month. And based on the past two years’ performance, I wouldn’t be surprised if it kept going for at least another couple of years.