When I assembled my new frame a few months back, I machined a one piece tapered steerer/stem spacer from a piece of delrin/acetal. The stock spacers I had were very clumsy looking.

At the time I did consider the material choice and concluded that being loaded in compression only it would be fine. Carbon spacers are commonly used, the epoxy giving the compressive strength and in this respect delrin must be about comparable with Epoxy. I chose delrin over alloy as it is black and will not tarnish.

I have been riding the bike for months now with no problem, no loosening of the headset etc, but for some reason I am now having doubts. Does anyone have a view on this?

Spacer can be seen in this pic:

I am somewhat biased against that just because I would worry it would break.

I have used aluminum and stainless tubing.

It is not going to break, I was thinking it might have a little 'give' allowing the stem to rotate more under impact and flex the steerer tube.

I wish I could buy single piece tall spacers. I have an uncut steerer on a touring bike for comfortable more upright positioning (my personal preference isn't common or popular, I know) and the stacked spacers I use tend to produce pop and crackle noises now and then depending on terrain and speed. A tall single piece spacer would solve this. Hmm. I'll start my home brew plans.

There's not much pressure on spacers, is there - just whatever you preloaded it to be, right?

I'm no engineer, but it wouldn't bother me.

It wouldn't bother me either. Sounds like a good idea even. I sweat a lot and corrosion develops on the stem and spacers creating creaking noises and even corroding the spacer to the steerer tube. Chris King headsets have these thin plastic washers that help that situation but a plastic spacer would be even better I think.

I turned a one-piece bearing cap + spacer for my wife's bike out of Delrin-- and not even real delrin, but generic acetal homopolymer from McMaster-- and it's been on the bike for over 5 years.

Delrin is outstandingly strong, and should (and does) serve perfectly well as stem spacer material. I mean c'mon, I have some FSA branded spacers here made of acrylic.

From a plastic supplier:

Delrin behaves like most engineering materials in that as temperature increases, elongation increases and strength decreases. Delrin has a tensile strength at room temperature of 10,000 psi, no true yield point and a stiff flexural modulus of 410,000 psi.

Delrin has outstanding fatigue resistance, almost indefinitely withstanding cyclic compressive/tensile stressing 5,000 psi.

Delrin does not permanently deform or retain dents, and has good impact toughness. The higher molecular weight resin formulations will deliver even greater toughness.

The Delrin-steel coefficient of friction is very low (0.1-0.3), and friction values remain virtually unchanged over a wide range of temperatures, loads and relative surface speeds



Sounds like more spacers should use this material.

OK I am happy now, the spacer stays.

Delrin spacers are actually available it turn out.

Lighter than Carbon too - result!

Everything has been done before.

I have a Cadex frame cut up into pieces that were used in another project and I plan on using some of the tubes to make a single spacer around 30mm in length. Should work just fine. Though of using PVC pipe, but ID does not fit the steerer.