Re: outboard bearings, simple question

On Sun, 30 Sep 2007 09:33:50 -0000, Chalo <chalo.colina@xxxxxxxxx>
wrote:

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

Dear Chalo,

The original 1892 outboard bearings:

http://collection.rydjor.com/bikecollection/1892exp1.htm

You can see why they brought it inboard--I expect that you'd tear it
off with one good stomp.

Plus . . .

--daylight showing through inch-pitch chain and sprocket

--cool half-link style chain

--direct-pull spokes

--solid red rubber tire eliminates all inflation questions

--clamp-on front fork coasting pegs for comfortable downhill riding

--slotted crank-footpeg interface for perfect adjustment

--high-capacity water-carbide headlight

--innovative front brake designed to avoid wearing out costly rims

Cheers,

Carl Fogel
.

Relevant Pages

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