Hi All,
Amidst the festivities of the New Year, my thoughts turned to the best ways to prevent my bicycle bolts loosening. I've had good luck using liquid- or tape-based thread-locking compounds, typically the "blue" formulas (i.e. LocTite's 242-series in liquid or tape form; they allow deliberate disassembly using hand tools). I've also had surprisingly good luck using pre-kneaded beeswax to secure headsets on threaded forks for use with quill stems. Kneading the beeswax by hand prior to application prevents chipping, flaking, and cracking, and allows it to mold into the clean, dry valleys of the threads, making for a more secure fit. For a "natural" product it works amazingly well in that application.
Without thread-locking compounds, my bicycle bolts tend to loosen fairly quickly when cycling on really rough roads of the type Andy Blance refers to as "South American ripio" (what I would call really bad washboard here in the States). To combat the problem (say, when mounting racks), I have taken to leaving my bolts long enough to extend past the far ends of their mounting bosses, and threading on a nylock nut in opposition, flat washers preventing direct contact with painted surfaces. This works nicely, has never loosened, and is easily field-serviceable. In the event a bolt breaks, there is enough of a stub to easily unscrew it using locking pliers. I have given up on lock-washers; for me, joints connected with them loosen more quickly than without. Even plain flat washers have that effect to a lesser degree, though they are often necessary to protect the underlying surface (paint or soft aluminum).
It turns out my empirical observations have some validity, according to the Bolt Science website:
http://www.boltscience.com/index.htmOf particular interest are the following pages from that site:
http://www.boltscience.com/pages/vibloose.htm (vibration loosing of threaded bolts and fasteners)
http://www.boltscience.com/pages/junkertestvideo.htm (a video showing self-loosening of threaded fasteners
http://www.boltscience.com/pages/twonuts.htm (double-nut locking)
http://www.boltscience.com/pages/helicalspringwashers.htm (tests of helical spring lock washers)
This last link indicates use of a lock washer or even a flat washer can, indeed, encourage fastener movement under vibration.
Of specific interest to me is their research indicating lateral movement of the secured parts (secondary to vibration) are a primary cause of loosening. This has implications for Sherpa owners who are running Thorn Low-Loader Mark V front pannier racks. The racks are drilled for 6mm bolts, and our forks are threaded for 5mm bolts. It is therefore of great importance to use thread-locking compound on these connections to prevent loosening of the oversized joint. If you have mounted your front pannier racks yourself, it might be a good idea to undo the fasteners, apply some thread-locking compound, and reassemble. A good New Year's resolution -- check those bolts!
Best,
Dan.
