I have two rear hubs here, complete except for axles, cones and bearings. I'm ready to re-build them, and need some clarification on cone specs. I can't understand why any hub which uses the same size bearing as the next one would have a different cone profile. The hubs are a Deore and a tri-color. Can anybody explain that? And would a 6600 hub use a different profile cone than a 6400?
TIA

The 3D surface curves that make a cup and cone system are based on bearing contact angle and overall rolling diameter. Then there's the cone's OD matching the hub's dust caps ID. Andy

I get the OD part, but don't understand the profile. Does it actually change with contact angle, or will the same profile provide differing contact angles?

While there is some range of differing contact angle that "works" on the same cone (and it's curved rolling surface) the cone is designed with an ideal contact point. More to the premature failure potential is where along the rolling curved surface do the balls contact. This is what I tried to suggest before. I've seen many hub cups/cones combos which have the balls contacting the very edge of the curved surface, the small end. This leaves little (or no if to the extreme) cone mass under the balls and the cone can pit/chip/crack far sooner then if the balls contacted the cove more at it's middle of the curve. As you can't see this when the hub is reassembled and sometimes not feel the axle's spin as being different then intended (until the damage starts/grows) one can adjust and ride in the false belief that all is good again.

When one is on a tour, or otherwise at the mercy of having to make do, one will use whatever is at hand, regardless of the long term results. But this isn't the way better shops work. We strive to do the right job the first time. (The meager margins that retail has get eaten up fast if the job is done a second time at N/C due to the wrong cone choice the first time).

In the early 1980s as the Asian wave came over the US market the contact angle changes were beginning to be known about by others then the designers. We saw many Atom/Normandy hubs for service, being the common from the years before, and mistakenly tried the newly available Shimano cones with bad results. IIRC the Euro contact angles were around 38* and the Shimano's were about 22*. These details are generally unknown to the typical home wrench and if the shop guy is also clueless... the home guy gets the wrong cones. Andy

But as usual, your results might vary. Andy

Thanks loads, Andy. One of the reasons I ask is due to my location. I can't just order from Wheels Mfg., and have any thought that they would arrive here, even if they would ship. You've answered the question beautifully.