> They appear to be a design success in that they are lighter and more
> rigid than earlier cranks and BBs. The jury is still out on long-term
> durability, but indications suggest that they are better than the last
> generation of 22mm "pipe spindle" bottom brackets with inside-the-
> shell bearings.
Fortunately, there's one piece of incorrect information in your post. The
new design tends to be a bit heavier, not lighter, than the lighter
in-the-shell bearing designs. For example, my FSA carbon with ISIS Ti bottom
bracket is considerably lighter than nearly all of the current offerings.
I say "fortunately" you're incorrect about the new designs being lighter
because I think it's a very good thing that we've seen at least one area
where something other than ultra-light weigh has won the hearts & minds of
the designers. Durability & stiffness seem to be the driving force behind
the new cranks, and that, to me, is a very good thing. Stiffer cranks
doesn't just mean it feel better when you stomp on it; it also shifts better
because the chainrings aren't moving around so much. And durability is an
obvious good thing (although, for reasons I can't figure out, I'm still
riding an FSA Ti bb that probably has 25-30k miles on it.
--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com
"Chalo" <
[email protected]> wrote in message
news:
[email protected]...
> jp wrote:
>>
>> here is a simple question: whats all this about 'outboard bearings'?
>> this is in reference to bbs and cranks. this is something that i
>> could google, but i'd rather get the forum response. i hear about
>> them here more than anywhere else.
>
> They are a relatively new approach to coping with the size constraints
> of the venerable British threaded bottom bracket shell.
>
> British, Italian, French and other similar threaded shells have only
> enough room for a passable set of bearings supporting a slender
> (16-17mm), nearly solid steel spindle. Making bottom brackets
> lighter, stiffer, and stronger requires a larger spindle diameter than
> the old shell design supports. Over the last ten years or so, larger
> 22mm spindles came into use along with very thin-section bearings.
> The spindles varied in success, but the bearings have proven to be
> less reliable than earlier designs.
>
> Around 1990, Magic Motorcycle made cranks with a 25mm spindle and
> bearings held in threaded cups just outside the bottom bracket shell.
> Recently, Shimano, Campagnolo, FSA, and others have come to market
> with designs that use Magic Motorcycle style outboard bearing cups.
> The new generation of cranks uses 24mm spindles with shims to center
> them in the 25mm bearings.
>
> All these designs are compatible with threaded BB shells, but none of
> the cranks, spindles, or bearing cups are compatible with earlier
> crank and BB designs. They must be used together as a system.
>
> They appear to be a design success in that they are lighter and more
> rigid than earlier cranks and BBs. The jury is still out on long-term
> durability, but indications suggest that they are better than the last
> generation of 22mm "pipe spindle" bottom brackets with inside-the-
> shell bearings.
>
> Chalo
>