Bottom Bracket Evolution

Interbike coverage starts September 14th, but there’s still time to submit questions and requests about new products. I’m there to be your eyes and ears, and knees and elbows, too.

Question: I had an old Gary Fisher with a press-fit bottom bracket, and replacing it was a crazy pain in the ass. (Plus it was basically just two bearings, and the bearings were garbage so everything had to be replaced every couple years.) Now I see this horrible idea resurfacing like a bad hippie flashback. Is this just retro stupidity, or have things actually gotten better?

Answer:
Gary Fisher really is a visionary, it’s just that at some periods in his life he was wearing those little, diamond-shaped, red-tinted glasses, and some things weren’t entirely in focus. Seriously, he never stops trying to build a better mousetrap, and he was painfully ahead of the curve on some things (bottom-brackets, sure, but also oversized head tubes). Pushing forward on standards causes plenty of headaches, but sometimes it makes for breakthroughs. For a while there around 2003, Trek seemed to be relegating Fisher to a tent out in the back of their real offices, until everyone started shopping at the tent (remember Trek’s STP vs. Fisher’s Sugar? Trek’s 69ers vs. Fisher’s 29ers?). The guy knows stuff.

So there was a logic to that first attempt at an alternate kind of bottom-bracket, but you’re completely right in hating those things. They were awful. Compared to what we have these days, those original snap-in bearing systems were not good.

Current systems are pretty good, though some of the same problems remain. The first problem is compatibility: when a new system is introduced, it creates problems for replacing parts. We have so many different “standards” on the market simultaneously right now, that it’s tough even to know which bottom bracket fits your new frame, let alone how good it is. Here’s a quick list of the most common ones:

1. BB30 uses circlips to hold bearings inside the frame’s bottom bracket shell, like those old systems, but, because both the bearings and frame’s shell are much larger, durability is much better, and stiffness is drastically better.
2. Press Fit BB30 is oversized, just like the standard BB30, but presses into the frame in a way similar to conventional headset cups.
3. Good Ol’ Threaded Cartridge systems were offered in both traditional square tapered spindle and various splined spindles, but have been all but completely replaced by external bearing systems, which share the same frame shell dimenions.
4. External Bearing bottom brackets thread into the frame just like cartridge systems, but have oversized bearings that sit outside the frame shell.
5. BB86 and BB90 systems are based on the BB30 concept, but use wider frame shells (86mm and 90mm, respectively).
6. Shimano’s 92mm press-fit bottom bracket presses into special 92mm wide frames in a way that’s very similar to headsets, and basically takes the External Bearing style cup system and makes the frame’s bottom bracket shell wide enough to swallow up the otherwise external bearings.
7. BB386EVO systems attempt to bring all this together by being both large diameter (like the BB30), and wide (like the 86, 90, and 92) systems.

Basically, we’re going bigger diameter and wider in everything, and the bigger diameter and wider shell make for a stiffer crankset, which really does improve your power output. But the increased size also allows us to get away with designs like the press-in system, that we previously couldn’t, when sizes were smaller and materials were inferior. Almost any system you go with these days is going to perform better than previous designs, and be more reliable as well. The evolution wasn’t always smooth or direct, but, overall, these new systems are better.