Old 06-29-19, 10:18 PM
Dave Mayer
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Originally Posted by MinnMan View Post

Felt noted that there was a spacer above the stem, and, I am told "disapproved", indicating that this over the long term can place undue stress on the steering tube.

(It is not clear that this was the cause of the failure in my case. There are other possibilities but they are besides the point of my question.)...

Having a spacer above the stem could not have caused the failure. Extra steerer tube above the stem places zero stress on the fork or the stem. Whoever 'disapproves' is simply making a poor attempt at deflecting blame.

The only downsides of having surplus steerer tube sticking out above the stem is a little extra weight, it is somewhat of a hazard to the (male) anatomy, and it looks dorky. I leave about 1cm of extra steerer above the stem, for the future flexibility of raising my stem.

In fact, it is good practice to put a 5mm spacer above the stem, held on by the top cap. Why? because it indicates to mechanics that the full width of the stem is securely clamped to the steerer tube.

I volunteer at a high volume city bike Co-op, and we see many horror shows of stems being half-way clamped onto steerer tubes. In fact every time we see a threadless system without a spacer on top, we remove the top cap to see if the stem is adequately secured to the steerer tube, or whether it is: 'hanging on by a thread'.

Carbon steerer tubes... you CANNOT install a star-nut in these. You need a carbon-specific expander system. Once the headset bearings are properly loaded, and the stem bolts secured, the expander can in fact be removed. It does NOT provide structural integrity benefit to the system. The expander and top cap ONLY exists to allow the headset bearings to be properly loaded.
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