Adjustable Length Bicycle Stem

Nearly four years ago I started training for my first triathlon. I rushed out and found the best deal on a road bike but I could find. Why a road bike? Yes of course, because I couldn’t afford a triathlon bike at the time. While I’m ashamed to admit this fact, I’m sure I’m not entirely alone. In my haste, I rode a number of bikes and still managed to select one with frame that was too large for my build. This became readily apparent when I was first fit (or at least fit as good as possible) to that bike.

According to my fitter, a good fitting for that road bike required some adjustments to the stem.  As you may be aware, adjustability in the stem area is a one-way in which a bike fitter can better optimize the stack and reach to your body.

Today’s article pertains to a recently issued patent for an adjustable stem.

It is not uncommon to purchase a stem for your bike based upon a number of specifications including weight, length, and rise.  The ‘rise’ is the angular measurement between the stem and the head tube (more specifically, the absolute value of 90 degrees minus the total angle between the stem and head tube).  Thus for example, a stem with a 6 degree rise may be installed with a 96 degree angle between the stem and head tube OR, if it is inverted, with an 84 degree angle between the stem/head tube.

The invention provides a single stem with a variable rise.  The stem body 2 below is shown nearly perpendicular (or 0 degree rise) with respect to the head tube or steering tube 6 in FIG. 1.

Below, FIG. 2 illustrates a means for tightening 9 the stem 2 to a pivoting tube 4 (which is the tube which rotates within the steering tube 6).  The tightening means 9 uses a wedge 19 which is secured by a tightening screw 21.  And this tightening means 9 may be adjusted to various rises or angles.

In addition, FIG. 2 illustrates a U-shaped cap 27 rotatable about axis 29 for securing the handlebars 26 using a pair of spacers 35.  The U-shaped cap 27 is at least partially intended to simplify adjustment.

FIGS. 5 and 6 illustrate the adjustability of the stem to achieve variations in the rise.

The patent includes another embodiment (FIG. 9) where the spacer 35 extends the entire width of the stem body 2 and connecting means (see 33, 34) are in a different arrangement.  It appears that this particular embodiment may be commercially available and is titled the “C-Stem”.

Today’s patent (U.S. Pat. 8,177,249) was issued on May 15, 2012. The full text may be found here (last visited May 23, 2012).  The patent is owned by Look Cycle International (Nevers, France).

The Legal Disclaimer:  I write this blog without taking a position as to the usefulness, desirability, novelty, aesthetics, functionality, etc. of the products or processes discussed in my posts. Naturally, readers are free to take any position they prefer and comment accordingly, provided it is in good taste. However, if I am silent with respect to your comment, such silence should not be construed as any agreement or disagreement to the comment; I hope you can appreciate that I simply prefer to remain neutral in such matters and merely report Patent Office & triathlon-related news. Thanks! 🙂

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