I am installing a new fork, and learning about threadless headsets. I like the height of the steering tube as it is, and if I get the Exotics 32-40mm spacer, I won't have to have to cut. The other option is to stack various spacers and shorten one of them.

I don't care about weight here. Is the adjustable unit going to keep its dimensions when compressed?

Spacer(s) work perfectly fine and I use them all the time instead of cutting the fork. That way if I want to change the height a bit I can or if I want to change stems I can. Roger

Try this one : Problem Solvers

Maybe apply thread lock compound It will let you adjust it once , initially, before it Cures,

Heat makes the chemical break down, taking it off and heating it, later, will be simple to do..



you can put spacers above the stem too ..

The only adjustable spacer I've ever uses was Easton's "Bear Trap" which was adjustable over a small range and used to set headset preload in place of a top cap bolt. It didn't work at all well and tended to vibrate loose during every ride. I very quickly replaced it with a normal expander plug and top cap. The Problem Solvers adjustable spacer fietebob linked to works similarly but seems to be a more reliable design.

Actually building a conventional spacer stack to your exact requirements should be easy as they come in a wide variety of thicknesses starting as thin as 2 mm and up to 40 mm. Also, the gap between the top of the steerer and stem isn't that critical as anything in the 2-3 mm range is fine. You can, and probably should, have a spacer above the stem to assure the steerer is fully within the stem's clamp.

Thank you for the inputs.

I bought the Exotics spacer anyway for $10 as I would have had to some extra spacers anyway, and maybe grind them down to avoid cutting the tube. The adjustable spacer resembles a piece of plumbing ... two hex pieces that thread into each other. It is alloy and the action is smooth. Easy install. I like that part of it.

Unfortunately, I found the stem I bought last winter was for a road bike, and since I didn't want to use handlebar shims to go from 25mm to 31mm, I will have to get another stem. Good thing I didn't have to cut. as I can adjust the height for the next one.

It is not that precise of a process. Being within a few mms is fine. Just get it close (steerer tube needs to be a bit below the top of the stem), set preload and tighten the stem.

See Sheldon Brown:
[h=3]Hands Up (Or Down)! Adjusting Handlebar Stem Height on Your Bicycle
Threadless Without Spacers[/h]

Man, do I hate threadless steerer tubes and their corresponding headsets and stems! What was wrong with the old threaded headsets and the quill-style stems? They allowed precision adjustment of the headset and you could raise and lower the stem/bars without having to take things apart, add/remove spacers, possibly cut the steerer and re-tension the headset. What a pain!

When I get on my bike in the spring, after the winter hiatus, I want the handlebars somewhat higher than later in the season when my body can handle a lower position. I want to micro-adjust the stem/bars - easily - without the possibility of impaling myself on the steerer!

I hate threadless headsets etc.! Did I already say that!?

i wouldn't say i hate them, but i do find it pretty irritating that you're supposed to check for the proper headset tension by holding the front brake and leaning forward and back, yet during all that your stem is probably not gonna be clamped to the steerer unless you like tightening it and un tightening it every time you make an adjustment to the headset, and that can make it feel wobbly just like a loose headset. seems kinda convoluted.

It's really not any more complicated than adjusting a threaded headset. For threadless all you need is one or two hex keys. For threaded headsets you need two headset wrench. As an on-the-road repair you are much more likely to have the needed hex wrenches with you.