Thus spake Bob Hovey:
>In today's parlance, I believe that any elbow-shaped stem that goes inside
>the steering tube is referred to as a quill stem.
Right.
>Interesting thing about the expander... back in the day, we used to associate
>the slant wedge expander with cheap stems, as you mentioned.
Yes. I believe this change was brought about by CPSC (U.S. Consumer Product Safety Commission) standards, which had an erroneous perception that the traditional expander system didn't hold the stem securely enough. Actually, the stem shouldn't be super tight, it should be loose enough that the handlebars will twist sideways when the bike hits the ground in a crash. This reduces the chance of damaging the handlebars or brake levers.
For actual riding, the torsional loading on this connection is not actually very high, so it does not need to be super tight, but the boneheads at the CPSC didn't realize this.
Wedge type stems usually have vertical serrations on the curved surface of the wedge, which do get a stronger grip on the inside of the steerer.
When the expander system was introduced, all stems were steel. This design makes more sense with steel than it does with aluminium. Steel quills have thinner walls than aluminium ones of equal strength, and steel is happier with repeated flexing than aluminum is. I've seen aluminium wedge stems where the bottom had fractured.
John Betmanis wrote:
> (Actually, "back in the day", we
> > called stems "extensions". "Stems" had virtualy no extension and were found
> > on common roadsters.)
I think that's more of a British usage/distinction.
It reminds me of the French, where there is no generic word for "handlebar." Instead, they have one word, "guidon" for drop bars; another, "cintre" for upright bars.
Actually, back in the day, the more common U.S. usage was
"gooseneck." Even today in the BMX world, "neck" is the prevailing
term.
>>I always thought of the expanding hollow stem as being more elegant than
>>the wedge, which to me seemed rather agricultural.
It is certainly more expensive to manufacture, especially in aluminium because an additional machining step is required to create the taper in the bottom of the quill. With steel stems, the walls are thin enough that this is not needed.
Sheldon "Cyclexicographer" Brown
+-----------------------------------------+
| Man invented language to satisfy his |
| deep need to complain. -- Lily Tomlin |
+-----------------------------------------+
--
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com
Useful articles about bicycles and cycling
http://sheldonbrown.com