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I picked up one of these Delta threadless stem risers / steer tube extenders so I could try out different handle bars heights on my gravel bike without going through a bunch of stems (since shops near me aren't open for a proper bike fit).

enter image description here

I got it used and really cheap, but it's missing the plastic threaded "stem cap" (see picture). It's not a functional stem cap, per se, as the stem cap bolt actually threads through down inside by the clamp. I guess it's really more of a dust cover, and it threads into the top of the unit instead of being held in place by a bolt. The guy I got it from said it's a generic part that should be easy to replace. But I can't really figure out what it's called so I can order one online. The manufacture has not been helpful thus far.

There's a good chance I'll replace this setup with a proper riser stem once I figure out where I want my bars, so I'm more asking out of curiosity than an immediate need.

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    Just to do due diligence, you do know you cannot use these things on a carbon steerer tube, right? – Argenti Apparatus Jul 20 at 18:01
  • @ArgentiApparatus: Why not? Looks like it clamps to the tube in exactly the same way a stem would. – Michael Jul 21 at 6:46
  • @Michael there is increased leverage on the steerer tube – Argenti Apparatus Jul 21 at 9:44
  • @ArgentiApparatus: Yes, but I don’t see why the steerer tube material should play a role in that. An aluminium tube can be just as weak as a carbon one. In the end, considering you can have a 44cm wide (or even wider) handlebar, I’m not sure a few cm extension play a significant role at all. – Michael Jul 21 at 10:54
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According to the installation instructions the manufacturer calls this a "dust cover cap." As you note, this is not a headset or stem cap since it doesn't mechanically engage with the stem to preload the bearings.

A Google image search for the image you included found a bunch of pages on Amazon describing this as a "Delta Cycle stem raiser," and I found the instructions on the Delta Cycle page.

Unfortunately, it doesn't seem to be a generic part; I couldn't find a single instance of it being sold individually. Perhaps you could bodge something with a normal headset cap.

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  • Thanks! Never occurred to me to do an image search. Somehow the manufacturer's website never turned up when I was searching for the actual product either. Found the replacement part cap on their website. – MikeyC Jul 20 at 19:31
  • @MikeyC And checking their website for replacement parts is something that didn't occur to me. <facepalm/> :) – DavidW Jul 20 at 19:33

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