…So this doesn’t happen to you mid-ride.
While bike shops and warranty departments hate to hear it, this truly did happen while Just Riding Along (aka JRA). Coming around a corner, I put a mild amount of acceleration into my ride and instantly heard and felt a crunch. The bike came to an immediate stop. Looking down, I assumed the chain had simply fallen off or gotten jammed. It took a second to see what had really happened, and another few seconds to determine why.
Quite simply, one of the chainring bolts had apparently been missing for a while. Normally, having one bolt missing would lead to cyclical chain rub when at the extremes of the cassette with each pedal stroke. Whether it’s a testament to the stiffness of high end rings from SRAM (and, likely, other brands, too) or just weak legs, I don’t know, but I didn’t experience any early warnings until *POW* things went south quickly.
Upon inspection, I did find the second chainring bolt that had popped out and actually caused the small ring to fold under a (honestly) fairly light pedal stroke. When I finally pulled them off, both of the other two bolts were in various states of looseness, too…
The other two bolts weren’t quite as loose as the one shown here, but it was visibly loose to the point where I could rotate it with my fingers.
With cranksets like SRAM XX that uses two sets of bolts, one each for the big and little ring, tightening the bolts is easily done with a single allen wrench. If you don’t have a torque wrench, just do them until they’re snug. Otherwise check the manufacturer’s recommended settings and get them torqued properly.
If your crankset uses a single set of bolts for both rings, you’ll likely need a specialty tool like Park Tool’s Chain Nut Wrench. Thankfully, it’s one specialty tool that’s cheap, about $4 to $7. This tool holds the nut on the inside of the chainring still while you loosen/tighten the bolt with an allen wrench.
If this does happen, usually you can just put it onto the other chainring and get out of the trail. And who knows, you may just find out you’re perfectly fine with a single ring up front. Hooray, weight savings!