Originally Posted by
Duragrouch
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I'll also add, folders typically have fail-safes, secondary latches, to prevent coming undone while riding. I don't see one on the coupler above. I would have designed a spring-loaded collar or lever that engages the spanner wrench cutouts, or an additional part that can be added to lock things. Or at the very least, once put together, put bright nail polish on both sides of the interface (should stay close position each time), easily seen when riding, as a quick check.
I have only had a coupler come loose on my S&S bike once. Since then I have always carried a coupler wrench with me.
I noticed it because when I was taking my bike outside the front door on my condo, when I dropped the rear wheel on the ground, instead of that bouncing noise it also made a noise I was not used to hearing so I looked to see what was causing that, it was the looseness in the downtube coupler that caused the new additional noise.
I put sleeves from inner tube rubber over each end of the S&S "nut" to keep the dirt out of the threads. That also would make it harder for the threads to start unthreading by themselves from vibration. I previously had this photo in post 5, above, you can see the rubber sleeves.
I have never heard of anyone riding a bike and having the two halves come apart, but I suspect if the downtube coupler was loose enough, the bike would handle poorly as a warning.