Massive, two....

Balls are arguably less than ideal for handling the thrust loads that a headset endures. Roller bearings are a superior choice for headsets, IMO.

Many of the small parts used in Suntour's high-end Campagnolo-lookalike components were directly interchangeable with the Campy equivalents.

The guy behind Bullseye components evidently believed that conventional bottom bracket bearing designs were similarly less than optimal, so he designed a bottom bracket that included axial and radial bearings in separate retainers, for a total of four sets of (smaller than 1/4") caged bearing balls in each bottom bracket.

I know that only because the sales rep brought a sample to show us, since we were already buying the Bullseye sealed hubs. (At the time, Phil hubs had to be sent back to the factory for maintenance, whereas Bullseye hubs required only an Allen key to remove the collars that held the bearings in place on the axle.)

Just did a search; looks like that Bullseye BB may never have made it into production, since all I can find are Bullseye BMX bottom brackets, which appear to be a hot item in the world of high-end BMX equipment. Guessing that when the sales reps showed that radical bottom bracket design to bike shop guys like me without a background in materials engineering, they got a shrug and a "no thanks."

Stronglight made a roller bearing bottom bracket, way back in the cottered crank days. Two sets of rollers: one to handle axial loads, the other to handle radial loads. It never really caught on; reports were that it was very fussy about alignment.


https://thecabe.com/forum/threads/st...tation.247216/

I imagine it would be fussy, we repeatedly see (thanks Hambini) that even modern high-tech manufacturers can't get their bottom brackets straight and concentric. I do wonder why they went for doubled-up bearings rather opposing tapers, maybe just the availability of standard bearings that would fit, or perhaps the separate axial and radial bearings were lower friction.

roller bearings also introduce a lot of drag, compared to ball bearings.... and yep, getting that one above set up correctly would not be fun, especially considering MFG. slop and the ever-changing conditions bikes experience...
those thrust bearings are overkill, IMO.. a plain bi-metal bushing would be enough, i'd think.
the loading is more a twist than a side shift.

tapered rollers see-saw, or "slider rocker", under odd, twisting loadings, are expensive to make, need to be paired as an assembly. and are fairly high drag too.

Yeah, that's why I think rollers are more appropriate for a headset than a bottom bracket. Unlike bottom brackets, or other bicycle bearings, for that matter, headsets are not in continuous rotation when in use, so the additional friction is far less pertinent.

under extreme pressures/shocking, small, "Low Count" roller bearings can shatter.
automotive U-joints use longer needle bearings, and as many as they can fit in the cups... they are also low rotation, low twisting load, and high friction.
i've watched people try to re-use a cup after screwing one up on a new u-joint... the cups are matched to the assembly, and shouldn't be reused on a different assembly.

the precision bearings honda uses in their transmissions and engines, in general, come in varying tolerances, depending on WHERE they're used... a tight press fit into a casting compresses the outer race... retainer installs were tighter than press fits...etc.
we would carefully measure the crank bearing bores in the cases, after normalizing the case temp, before ordering the correct toyo crank bearings for race engines.