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Threadless Stem...How does it work?(11 posts)

Threadless Stem...How does it work?Jedi
Jun 26, 2001 9:42 AM
Ok, I'm behind the times and still ride on a threaded fork, but I'm looking at getting a new threadless fork. I can see the basic principal, the stem clamps on to the steerer tube and you tighten. But how do you ensure a very tight no gap connection between the stem and the headset bearings/races so there is no "slop" in the fork and headtube? On a threaded set you can turn/tighten the large nuts on the headset and the quill on the stem ensures a tight "in the tube" bond with the steerer. is there a good Tech site on the Web that I can review??
Thanks
Like this....muncher
Jun 26, 2001 10:10 AM
The nut in the middle of the "cap" on the top of the tube is on the end of a spindle which runs down the tube, into a bracket (the "star-fangled nut") in the middle. When you screw it down, it pulls down against the cap, squashing it down against the tube, trapping the stem tight against the headset. When it's tight enought to stop free play, you tighten the squeeze bolts on the stem, and it grips the top of the tube, keeping the whole thing tight. Simple. I'm sure Sheldon Brown would oblige....
Like this....Jedi
Jun 26, 2001 11:23 AM
Great!!!
Thanks for the explanation...I understand completely now.
OK..another question...PaulCL
Jun 26, 2001 12:47 PM
why did the market ever go to threadless in the first place?? Are they lighter, safer, stronger??? I don't see the advantage. They are "bulkier" looking and IMHO, not as good looking as the threaded ones. Just curious.
OK..another question...Eames
Jun 26, 2001 1:23 PM
Threadless can be as much as 1/2 pound lighter. I don't see that they are safer or stronger. In fact w/ All-Carbon forks I wonder if they are as safe. Two other reasons the market switched. In general we deal with a fairly flat demand curve. Hence companies are always trying to stimulate the market with new toys ( the reason most people buy ). The other reason is that LBSes find it easier to install. I can't count the number of people working in a LBS which have sworn by threadless.
OK..another question...Jofa
Jun 26, 2001 1:25 PM
There is a marginal weight saving. Strength isn't an issue as nothing ever failed here anyway. There were corrosion problems with the old quill type: because the clamping mechanism is always at the bottom of the quill extension, whether the old Cinelli XA 'spreader' or the more standard 'wedge' design, there was an oppurtunity for water (in this situ, salty sweat) to enter at the junction of the stem/steerer tube, and by cappilary action to leach down into the steerer. O rings have been tried to prevent this but never worked properly. The net effect is that quill stems are inclined irreperably to seize solid inside steerers... more so than seatposts, but they are reported less because attempts to adjust stems are fewer. IMO the modern Ahead design is preferable, but I'll agree with you about the aesthetics, and if I was building up a pretty skinny steel bike I'd stay with a quill stem for this reason; in fact I'd use a Cinelli XA because they look nice even though they're poorly designed in most respects.
The 'stiffness' angle, I suspect is irrelevant, though I've not seen any data to confirm this.
Good PointsPaulCL
Jun 26, 2001 6:44 PM
Regardless of what I think, the facts remain -quills are going the way of toe straps. I am not going to "upgrade" (I use that term lightly) my current quill stem. Also, that day out in the future when I invest (invest?) in a new bike, I'll have to get threadless since threaded just won't be available. Oh well, I was just curious. Thanks for the replies.

P.S. If I honestly believed that it would save me a half pound, I might consider a change in the future. That would put my ride in the sub-15lb class! I'm not enough of a weight weenie to throw away a perfectly good fork, stem, headset, etc to save 1/2 pound. I can lose 20 times that around my gut first!
1/2 poundrailer
Jun 27, 2001 5:10 PM
WHat fork and stem are you using? Threaded forks have to have steel or ti steerer tubes which are substantially heavier than a full carbon fork. Your stem probably weighs around 280 grams also. You can easily buy a threadless stem that weighs 140 and there is even one that weighs 95 grams, although I refrain from installing this item as I would like to keep my face the way it is. I currently use an aluminum stem that weighs 147 grams.
I recently weighed...railer
Jun 27, 2001 5:14 PM
a couple forks. One was a carbon with a steel steerer and the other was a LOOK HSC1 with a Dura Ace caliper still attached. The LOOK was still lighter even with the brake mounted.
1/2 poundEames
Jun 28, 2001 1:03 PM
I haven't done the math as to how much weight I would shave off. The 1/2 pound figure was given to me by someone at an LBS I trust. However it doesn't seem to far off the mark. I ride a 63cm steel frame & fork. That means a large headtube = large steerer on the fork. I've seen steel forks at 500g and all carbon forks at 350g. If I loose another 50g on the stem and headset I'm at 1/2 pound easy. Correct me if I'm wrong but 1 pound ~ 400g.
couple of points to consider ...bianchi boy
Jun 28, 2001 8:38 AM
Threadless forks/stems have some serious drawbacks that are often glossed over. The main problem is that you can't raise the height of the handlebar/stem once you've cut the fork steerer tube. Also, if you prefer to ride with your handlebars fairly close to the height of your saddle, you have to add a bunch of spacers to the threadless setup to get the proper height. This looks crappy and is a safety concern if you have a carbon steerer tube, which shouldn't have more than about 1.5 cm of spacers or so. Threadless proponents say you can get around this problem by installing a stem with positive rise (eg, 90 or +17), but this looks rather clunky and it's hard figuring out the correct stem length and rise.

I just bought a new steel frame with threadless fork and stem. To get the handlebar at the height I prefer, my steerer tube has about 2.5" of spacers. I don't believe this setup is saving me any weight compared to a threaded fork/stem because the steel steerer tube on my fork must weight at least as much as a quill stem. I also don't like the way it looks compared to a quill. To make a long story short, I will probably have the shop order me a new threaded fork and stem and swap it for the threadless setup -- which unfortunately is becoming the standard now. I have ridden bikes with threaded stems for 25 years and never had a problem with one coming loose or not being stiff enough. But I have had a whole slew of fit problems ever since buying a bike with a threadless fork and stem.