My Bianchi Pista came with threadless headset, and this has allowed me to play with quite a few stem configurations without spending too much money.
Now I know what works for me and I could probably duplicate the position my present stem gives me if I chose, on my next bike, to go with a threaded headset, instead.
Aesthetics aside, does either threaded or threadless have any advantage over the other?

a threadless setup tends to be lighter and stiffer. i also find headset adjustment to be waaay easier on a threadless.

Here is what Jobst brandt thinks:

Subject: Threadless Headsets
Date: October 30, 2004
From: Jobst Brandt Although roller bearing headsets
Threadless headsets are a welcome and major improvement over the quill handlebar stem and the large octagonal head bearing nuts that fit on threaded steertubes. Besides, the quill stem was never adequately attached to the fork, moving radially at its upper end, where it had a loose fit in the steertube.

The need for special wrenches to adjust head bearings was cumbersome, but was more an inconvenience than a functional failing, one for which the threadless design is an ideal solution. Attachment problems, head bearing adjustment, and the greater force exerted on stems with MTB handlebars demanded a design change.

Upper stem movement, although small, pumped perspiration enriched rain water into the interface and on occasion froze aluminum quill stems in the steertube. They became stuck and sometimes unremovable because aluminum oxide has a greater volume than aluminum and, at times, expanded with enough force to cause a bulge in the steertube. Such an interference fit can make removal by force impossible and in many cases requires machining.

The threadless steertube solved these problems elegantly. The stem is clamped to the outside of the steertube with one or twoAllen screws to give a rigid interface. The head bearing is centered on the steertube by a conical ring that is pressed into engagement by a sleeve beneath the stem, and clamping the stem locks the adjustment.

Failsafe clamping is important in selecting a threadless stem. Unlike the quill stem, where an attachment screw failure caused a loose handlebar, the threadless stem handlebar clamp can completely separate in the event of failure, if it uses only one pair of screws. Therefore, a steertube clamp with two screws and the handlebar clamp with four screws is preferable.

When converting from a quill stem, the improvement is most noticeable in that the entire bicycle seems to become more rigid, especially when accelerating or climbing hills standing. Maintenance of head bearings and removal of handlebars, without untaping handlebars or removing brake levers, becomes trivial.

The shortcoming is that handlebar height cannot easily be changed without a special stem, one with an articulated extension. This is not a problem for people who know what handlebar height they want. It seems to be more a problem for new riders or rental bicycles that require adjustable height.

Threadless, so they say, is better for a couple of reasons. It is stiffer and appearently with a quill stem water can work it's way in and cause rust.
I like threaded stems for my fixie because I can change handlebars very easily. I have 3 types of bars on stems for easy switching.

Threadless is marginally lighter I believe. More importantly, it's stiffer. It was invented for offroading where traditional quill stems had way too much flex to them and migrated to road racing and new track styles.

you can switch bars just as fast on threadless stems. Threaded stems look better though - a lot better!

While I used to love threaded, I cannot argue with the ease and comfort of a threadless set-up. Adjusting the headset is easy. Changing from bullhorns to drops is easy. While I'd probably go back depending on the frame (a lugged steel frame is in my future), threadless is choice.

I like threadless so much better.
- stiffer
- possibly lighter
- easier to maintain headset adjustment
- so many more options. I'm having the hardest time finding an inexpensive open faced quill stem that doesn't flop around like a wet noodle.

https://www.habcycles.com/techstuf.html#oneinch

"Also, it's been suggested that an 'over-stiff' steer tube concentrates stresses at the ends, rather than distributing along the entire length as well as a 1" steer tube might. And after all, the ends are where steer tubes will break, not in the middle."

I dont' know if I buy that. Personally, I like the looks of many quill stems, esp the Cinelli 1R and the Shimano DA (made by Nitto).

Deda Elementi Pista stem and chromoly bars are the only reason for making me switch.

if it's purely a matter of aesthetics, threaded by all means. the performance argument is one i'll choose to decline, however, as i've never ridden threadless.

Threaded is beauty threadless is fugly. That is all.

I ride both and don't notice any stiffness problems? I like the threaded because you can change the height. As far as looks go, I see the quill stem as elegant and lady like while the threadless is rather industrial and utilitarian. Each of course has a unique look.

I personally like the looks of threaded alot more, and the easy bar height adjustment with threaded stems. Finding new stems can be a problem sometimes though, especially if you want a certain look or size.
However, threadless is MUCH easier to adjust, greater range of stems available for cheap, and bar swaps are MUCH easier with a removable faceplate threadless stem.

Only two drawbacks to threadless: Lack of height options and complete and utter inelegant fugliness. I cannot stress this enough. Also, Jobst Brandt is a green-blooded Vulcan.

1. washers. how many times are you really going to adjust your stem height?
2. Is this really inelegant?


that said, I really do like threaded. it's just that there isn't a threaded stem to hold my bars.

Yes!

Oh, yeah, and washers stacked up above or below are _so_ pretty.

if you ride stree & track threadless is nice.
all you do is undo your front break bolt & remove faceplate
that way you don't have to readjust your front brake cable.

jeff

2nd thought - don't they make threaded quill stems with removable face plates?

do they make carbon fiber quill stems? j/k

jeff

man, i really hate lugged stems -- especially lugged threadless stems. that is totally excessive. oy vey. sorry if this isn't the proper forum for such venting, but the catharsis was necessary.

"washers. how many times are you really going to adjust your stem height? "

daily with threaded. Scootin round town, keep my stem one height. Gofast saturdays? drop it an inch or so. Ridin my little girl to get an icecream cone, raise it up an inch or so. During a century I might change my height several times in a single ride. Only takes about 8 seconds.

infinte (height) adjustability of the quill far outweighs the therotetical advantages of the threadless (imo)

agreed.

Yup. I keep that thing all the way down when I'm just moving around town. But last Sunday when we did the big ride, I raised it up about a cm or so to give me a little more comfortable long distance position.

And they do make threaded pop-top stems.

Aesthetically, I prefer threaded. I'll use whatever the bike comes with, though. Currently I'm at about half and half.

In other news, lugged stems are a goddamn atrocity, unless you're planning on running 3-speed bars with streamers.

Yea, I don't think I'd call that lugged threadless stem inelegant. Hideous beyond description maybe.
Aesthetics aside, I've never had a threadless on a road or track bike. I've never had a problem with excess aluminum oxide or my cumbersome special wrench to necessitate a switch from a quill. Guess I'm just lucky and good with my tool.