Just curious, I figure there has gotta be one. Thanks

Absolutely none at all. Both threaded and threadless do the job just fine. Threadless forks are less expensive to manufacture. IMHO that is why threadless has become standard.

Threadless advantages - lighter, easier to maintain. Disadvantages - stem height adjustment range depends on steerer length, although there are adapters to overcome this.

They are transplants from the ATB world, which nearly took over biking in the pre triathlon/pre Lance era.
In the early '90s ATB were outselling roadbikes 9:1. Manufactureres discovered that slant top tube bikes
were easier to stock as 3-4 sizes cover the market, where parallel top tube frames needed 6-8 sizes to cover the market. The threadless fork is one size fits all frames, just chop the head tube to size and use a few spacers to fit it to the bike, whereas threaded forks must be very close to the right length and shortening one risks buggering the threads hence are made to fit the frame So now you know why slant top tube frames are taking over the road bike world: so shops and frame makers can get by with smaller numbers of frame sizes and simplify their stocking.

Of course it helps that riders buy a lot of them as well. I will eventually get used to their look, but still
prefer the classic DF, parallel top tube bike. Slant top tube makes me think of gnus.
Steve

I have both. I think that the threadless system is a bit lighter and maybe a bit stiffer. Changing out the length of the stem can be a bit easier with threadless, and I like the ability to flip the stem to get the bars lower as my fitness improves over a season.

All that said, I like the look of a quill better.

I agree that the "innovation" of threadless was more an issue of manufacturers looking to be more efficient as far as the manufacturing process. I also agree that it was the mtb market that drove it, particularly with the suspension fork. And the fact that it became clear that aftermarket suspension forks would create more aftermarket fork business than had been present before. Makes more manufacturing sense to build forks with a long steerer tube that can be cut to size instead of making a whole bunch of different threaded lengths. And it is a very strong design (threadless fork/stem), so it does have merit as far as mtb's are concerned. Once the threadless thing caught on, it became obvious to the road bike sector it was the way to go, too, in terms of manufacturing efficiency. Just my .02

Still owning a bike I bought 25 years ago, I'm afraid threadless headsets are totally foreign to me, as is most of the stuff that's spilled over from the SUV, I mean MTB, world. How are these things adjusted with the same degree of precision you would adjust a threaded headset? Do they use ball bearings or tapered rollers?

One nice thing is these things do not require much precision to preload the bearings.....an allen wrench is all that's required.....no more huge headset wrenches..........especially on those very rare occassion where your headset loosens up while on the road...

Typically you can save about 1/4-lb by removing the quill and bolt that goes down into the steerer tube when going from threaded to threadless. Also clamping on the outside of the steerer gives you a larger diameter interface with more contact surface-area, leading to a stiffer joint with less flex. Try flexing the bars by standing facing the bike with your legs straddling the front-tyre. Grab both bar-ends and yank one up and push the other down. With a traditional 100mm Cinelli-type quill-stem, you'll be able to flex the bar-ends 2" up and down. With the stiffer threadless design, this flex will be about 1/2 of that or just 1".

I own one of each--that is, a newer bike with a threadless stem, and an older bike with a quill stem. Adjusting the quill couldn't be easier, and it looks great, IMHO. The trouble with threadless is that most are cut so low that riders are forced into a more radical position than makes sense for them. So it's not so much the technology, though I see little real advantage to the rider in it, as the range of adjustment that manufacturers provide when they cut the steerer.

Some silliness in some posts above.

Threadless headsets allow cost reductions in bicycle manufacturing. One fork (cut to length by the LBS) works for all frame sizes, and never needs to go through a threading operation.

Quill stems are easier to set up and adjust to the rider. They also allow the handlebar to be higher (yes there are cludges to make threadless stems higher).

Headset/stem weight is a red herring. You really have to consider how much difference it will make in your ride. Generally, the honest answer is none.

As to twisting a handlebar so that either end shifts 2", well that's just not goinjg to happen unless something is broken. And, that might be the rider. There is no way, standing in front of a bike, that anyone can stablize the steerer tube enough to tell of motion is caused by the stem bending, or the more likely culprits of the whole bike moving, or worst case, the front wheel being soft and bending.

There is so much silliness of stiffness that is just so much marketing brainwashing.

So, either headset type and stem works just fine.

Threadless, as someone has mentioned, are much easier to adjust in the field as they do not require two largeish wrenches. I just put an adapter on my bike, so that I still have the threaded headset, but now use a threadless-type stem. It is noticeabley stiffer (same bar, fork, wheels, etc).

I haven't quantified it scientifically, but you know how when you walk in sand or snow you feel like you're losing some energy to slippage? That's the kind of difference I noticed, like I had been walking in sand and now with the stiffer stem I am on firm ground and when I stand up to hammer up a short hill more of my energy is being used to move me forward.

Just because you've never experienced something, does not mean it doesn't happen. Because I've never gotten into a wreck in a Volvo, I'm not going to make any comments one way or the other about their relative safety in relation to Mercedes or BMW.

You can hook your toes around two spokes at the bottom of the rim, squeeze your knees on both sides of the wheel to keep the front-end stable and yank one bar-end up and push the other down. This is just with my arm strength, imagine an all-out sprint with the muscles from the legs and back being brought into this scenario:



The fact is, there's such a thing known as engineering, using terms like modulus-of-elasticity and equations that depict the polar moment-of-inertia (radial stiffness) of tubing. For any given design and material, you can calculate the amount of deflection based upon the loads (or just pull out a ruler and measure the distance from each bar-end to the fork-crown in those photos). There's a reason bikes aren't made from 3/4" diameter tubing and why softer materials like titanium or aluminium are made in larger diameters than steel.

In the 10-years I've worked at a shop, I must've seen over 50 snapped stems, all of them quill stems, never a threadless. Although I have seen a few threadless stems with stripped-out clamp bolts. I've snapped two quill-stems in finishing sprints at races and an SR handlebar too. Refer to Kirichenko's 1989 World Championship event... and you'll know why track guys use steel handlebars and stems...

There's a difference between facts and rationalization. It doesn't matter WHY something is designed or WHY it's used, you can come up with an infinite numbers of reasons on both sides. Here are just the general facts, regardless of "why":

QUILL STEMS
- heavier
- more flexible
- easier to twist in fork
- easier to adjust for height
- one-piece wrapping clamp tends to be quieter, although tougher to change bars
- looks cooler when horizontal without too much of a handlebar-drop

THREADLESS STEMS
- lighter
- stiffer
- harder to twist on fork (due to larger clamping area)
- tough to adjust for height without future planning during installatoin
- might not look as cool when adjusted for comfortable handlebar-drop
- easier to change bars, but 4-bolt clamp can squeak
- pretty much the only way to install a stem on an aluminium or CF steerer tube

There are pros and cons to both, you just have to pick a list of criteria that's important to you and find the system that best fits those criteria.

Yes, you can adjust them with the same amount of precision as threaded headsets. They also come in both ball-bearing and roller-bearing versions. I like the roller-bearings since they can withstand more load and lasts longer. Notice that on my bike above, I have the roller-bearing Stronglight threaded headset (62gm) and I've left enough extra steerer tube to use with a threadless stem if I wanted to...

That is the best summary I've heard to date anywhere. Good job.

Tim

And here i'll quote the most important attribute that makes threaded superior to threadless:

- looks cooler when horizontal without too much of a handlebar-drop

Threadless is just ugly as hell.

For tourists, the issue of weight saving in the tool departmant are the biggest difference. You can adjust and service threadless systems using standard carry-along allen keys.

Uh what.

Just pulled the last one in the thread, but really asking about a point I saw mentioned several times.

I have never had a threaded headset that needed adjustment... is it actually a weakness of threadless that they require occasional adjustment?

The only time I have ever adjusted a threaded headset is when I was repacking the bearings.

Danno, great run-down.
-
This is actually a good point. I've got a 32mm combo headset/pedal wrench from Park that weighs very little (about twice the thickness of a cone wrench), but it's still an extra thing to carry b/c threaded headset.

Unfortunately, I have. I have an S&S coupled travel bike that the headset loosened on while I was on a business trip and I didn't have a headset wrench. I wound up borrowing a 32 mm open end wrench from the plant where I was working to readjust it.

Since then I have always carried the Park travel headset/pedal wrench Tim describes above. It is a neat tool and very light. But, yes you are correct that this is a very rare problem.

However, if the stem is properly installed and tightened, threadless headsets very rarely need adjustment until they are disassembled intentionally so neither type is at a disadvantage here.

What about turning the handlebars when you are travelling how do you do this.

Take the front-wheel off and turn the bars & fork 90-degrees?

Good points. Just because it hasn't happened to me doesn't mean that it doesn't happen. But since I have never owned a threadless, I was curious.

Now I have another tool to buy and make sure that I have with me, just in case.

Thanks!

Best summary I've seen, too, DannoXYZ! Thanks!

Not exactly scientific, but true. Nothing beats a really nice quill stem for sheer beauty.


Tim