Can someone tell me about threadless headsets - why they were adopted over threaded headsets, why people have a big stack of spacers above the top cup instead of trimming the steerer tube, etc.

I just need a quick primer or a link to a web site.

The driving force is money (faster assembly time). Plus all quill stems made became, if not obsolete, useless for new bikes when 1 1/8" steerers came about. Many people leave their steerers long because they are either lazy or afraid to make the cut, they are unsure what length they want or value having vertical adjust-ability (a plus of the old quill stems - properly grease, changing height takes about two minutes)

Some of us consider the proper height of our handlebars a moving target. I vary mine for different rides and different fitness; something I have been doing for 40 years.

Ben

Moving target--a perfect description of leaving adjustability in a fork! Bravo!

In short, it is a better engineering solution for the steering system. Aesthetics are a different issue, but if you are tslking functionality the threadless system is a natural evolution:

-Lighter
-Quill stems tend to seize in steerer tubes if not greased regularly. No seizing issues with threadless
-Stem position and headset bearing tension adjustments are quicker and only require an allen key. No headset wrenches
-Locknut loosens commonly on threaded headsets, whereas the star nut and bolt that hold bearing tension on a threadless system don't generally come out of adjustment
-In a threaded system, fork and head tube and headset lengths and stack height dimensions must all match to fit, making fork or headset swaps difficult sometimes. A threadless fork steerer just needs to be long enough.
-No fork threads to get damaged on a threadless system

Also, for anybody who says the above are minor or fringe issues, if you leave the bubble of capable and obsessed C&V enthusiasts and work as a mechanic doing service in a bike shop you will see the above issues almost daily.

This.

I understand the advantages of the threadless steerer but I do enjoy the extra flex in a quill stem. Makes an old guy just a little bit more comfy.

While lighter weight and a stiffer steering assembly are definite benefits, the biggest benefit is that the setting is locked by tightening the stem, which does not affect bearing pre-load, unlike a headest with a threaded locknut. This eliminates trial and error, facilitating the process for novices and increasing profits at an LBS.

Also, the adjustments are accomplished with one small, light and inexpensive tool that can carried in a tyre sock or saddle bag in the rare event that on-road adjustment is required.

Most threadless headsets are also 1-1/8" size, so the larger diameter increases the bearing contact area, which decreases loads and increases life expectancy.

Height adjustment is not that much more difficult than a traditional quill stem. Provided the stem is left uncut, the height range can be just as large and is accomplished by moving spacers between the top and bottom of the stem.

The only arguable drawback is aesthetics and the beefy appearance can be preferable in some applications such as ATBs, frames with oversize tubes and monocoque carbon fibre frames.

Another way threadless saves money is that there are fewer fork sizes to make and stock.

Thanks to all. It was interesting for me to read.

The problem is most Backcountry mechanics do not know how to setup and adjust these headsets. Just about every one of these I have seen in Cambodia has been a basket case. Quill stems are just such an easy thing.

Um, those are opposites.

A big stack above the top cup means they want more height, and they sure don't want to trim the steerer tube.

With spacers, and the stem flipped "down," the look approximates a quill in some ways, and avoids what some consider an awkward look with the stem flipped "up."

Trimming the steerer tube is basically same principle, in reverse. They lower the steerer end to get the height they want. If the stem is flipped "down," this is often called "slammed." Some prefer that fit, some prefer that look. With the stem flipped "up," and the steerer trimmed down, the fit may be right, but many feel the look is awkward.

If it's all about fit, there is no wrong or right way. I have a friend who has spacers above and below the stem; he has no issues with the look at all.

If it's all about the look, there is no wrong or right way, despite what you may read on the Road forum.

There are many times when the low down "slammed" fit just does not work. Back problems, neck problems, fitness levels, body structure, etc, all combine to create a fit that a person needs, not always what some other person wants.

Fit your stem the way you want, tell the naysayers to go ride a bike.

"Road forum"??? What's that?

I only visit this forum. I once made the mistake of posting a question in the Mechanics Forum but will never do that again.