[bike] Odd failure yesterday

[dmaze]

Oh right, yesterday's ride had more than its share of bike failures. We lost a tire in outer Carlisle, and the tandem's rear chain needed to be reseated several miles later.

Ever since I've had it, the new bike's front derailleur has acted a little funny. It feels like the shifter has four positions, but there are only three chainrings, and getting it to act consistently takes a little effort. Somewhere in outer Acton, the shifting started to get really bad, and then the chain fell off the inner chainring. In the process of reseating it, I discovered that the entire pedal assembly shifted about a half inch side-to-side, which explained the current exceptional badness. On further examination, it seemed like the left-side crank was half an inch too far out, which is odd because repairing it required first moving the crank inwards and then screwing in a piece on the outside.

Question the first: is this something that could Just Happen? Or is it a possible problem when the bike was initially put together that I just haven't noticed, or something Wheelworks might have touched in the "30-day checkup" (a good 100 miles before this)?

Question the second: the screws that hold the crank on had strange blue stuff on them, and several of the parts around there have specific torques printed on them. Should I take the bike somewhere to have the crank taken off and put on again, or is what I'm able to accomplish with hand tools in my backpack good enough?

Comments

[nuclearpolymer.livejournal.com]

Was the blue stuff similar to the stuff on the screws that adjust how far left and right your brakes are centered? Sort of like teflon tape? Or some kind of goo?

I thought that torque guidelines were usually to prevent over-tightening when people use power tools, but not sure.

[dmaze]

I want to say it was goo, but I'm not really sure. There's a space in the middle of the crank and I could see that the screws there were blue, but more like black after futzing with it.

Between all this goo and tape and washers and what not...screws are more complicated than I can really handle, for one of the fundamental kinds of machines.

[nuclearpolymer.livejournal.com]

My impression is that one would apply goo to a screw that you wanted to be able to easily unscrew later, but that one would apply tape to a screw that you did not want to loosen. Teflon tape is used with plumbing or piping screws to make the seal more air-tight/water-tight. I believe a similar thing is used on at least some bike screws to prevent them from working loose. Although obviously it must not have worked if that's what you were seeing.

I would probably just be a high-maintenance customer and complain to the bike store and see what their theory is. I think that the summer sale starts next week, so you might want to avoid going during the mad rush.