I just had work done on my mountain bike (Trek 4500, about 3 yrs old) because the chainrings were coming loose from the crank. I think it was a loose spider ring maybe? Anyway, they tightened it up for me and charged 10 bucks and everything was good. 12 miles of riding later (after a few weeks) my right side crank comes loose. The hex bolt holdin on the crank (I assume that's what it does) is really loose. So I'm thinking that it's the LBS's fault because I've ridden the bike for years w/ no trouble, then they do some work (assuming they took the crank off to tighten the lockring) and it almost falls off 12 miles later. So I guess I'm kinda complaining, but I also want to know what to do. I'd take it to the shop, but that's a hassle and I guess it might not be their fault, so what do I need to do to fix it myself. Can I just tighten it back, or do I need to worry about sand/dirt having gotten inside somewhere, and then take it all apart, clean it, and put it back together? I pretty much stopped riding when I realized something was wrong, but it was a pretty sandy trail. And, can I just tighten the bolt down real tight, or does it really need to be a specific torque? Thanks, and sorry for the long message.