Impending Failure

For you bicycle tech heads — what is the expected result of 36 hole, 14 ga spokes, a 390 gm hard anodized ceramic rim with single eyelets used on the rear wheel of a tandem?

The biggest crack in the rim.  My fingers are probably three inches apart.

Something like that, I’d imagine. I thought that I heard a pop on my last ride that sounded like a spoke letting go. Around 1/3 of the circumference, the drive side spokes have pulled the inner part of the rim away from the rest of the sidewall. 6 cracks are clearly visible, I suspect others. This looks like brittle failure to me, probably after a sufficiently large crack initiator formed. I’m guessing that there has been about million cycles (1200 miles), which could put it into the fatigue category. I don’t have any of my materials references handy though, so that’s just a guess.

One of the smaller cracks in the rim.

I have had single eyelet Mavic rims do something similar to this on my road bike, but that was with the old MA rims. They were made out of a softer metal, not hard anodized, with a much more square profile. That rim just pulled a small section of the inner box wall out in a rather slow, progressive failure. This one seemed a little more dramatic.

I want the next rim on this thing to be T6 aluminum, not hard anodized, and double eyeleted. If I can find something even close, I’ll be suprised. A lot of bike wheel parts these days are designed for style — that’s the last thing that I need. Bit I’ll end up with whatever the shop decides to put on, since they are doing this on a warranty basis.

No comments

No comments yet. Be the first.

Leave a reply

You must be logged in to post a comment.