Mountain bikes' handlebar stems are a bit of a compromise. They put the bars at a length and angle that are generally good for most types of riding, but that aren't necessarily ideal for any one. While adjustable-angle stems do exist, most still don't let you change the length. Well, that's why Spain's 3FStech created the AIM stem. With the push of a button, it lets riders switch between three bar angles and reach lengths.
As can be seen above, the AIM features a downward-sloping rail-like section in front, which a separate anodized aluminum bracket slides up and down. The handlebar is mounted on the top of that bracket.
The bracket can be locked in one of three positions on the rail – all the way back, shifting the rider's weight toward the rear for downhill runs; part-way forward, allowing for a more aggressive stance when taking on relatively level trails; and, all the way down and to the front, keeping the weight forward and the center of gravity low when climbing hills.
Additionally, users on long rides may wish to switch between positions simply to avoid fatigue.
That switching is accomplished simply by pulling a bar-mounted trigger-style remote that temporarily releases the bracket, then pulling the handlebar up or pushing it down. Low-friction polymers on the facing surfaces of the rail and bracket help them to slide smoothly.
The stem itself weighs a claimed 350 grams, with the remote adding another 50.
If you're interested, the folks at 3FStech have taken to Kickstarter, to raise production funds for their device. A pledge of €175 (about US$191) will currently get you one, if all goes according to plans. The expected retail price is €275 ($300).
The AIM stem is demo'd in the video below.
Source: Kickstarter
The industry standard for climb vs descent modes is the travel-adjust fork. In the case of such forks, there is an added benefit of head tube angle change that improves maneuverability in climb mode and stability in descent mode. The stem in discussion does not change head tube angle at all.
Also, in a typical mountain bike crash where the front end gets spun around as the rider-less bike tumbles down the trail, I can see the end of the stem damaging very expensive carbon frames right on the top tube behind the headset. The only way to avoid this is to use excessively tall steerer and spacer combos.
At $190 it's questionable if this is a viable alternative to travel-adjust forks.