crank problem with new bike

[joshuaseu]

alright, getting annoyed here, yesterday, when i was riding and testing how my adjustments were working for me, the left crank fell off. the nut came unscrewed. i put it back on and tightened it, took it out to ride again and it got loose again, not to the point of falling off, so i read through the manual and it suggested taking a rubber mallet and lightly tapping the crank on securely, then tightening the nut back down, well, this made it last longer, but this morning on my way to work, it became loose again. i took the other crank apart to see if maybe a washer or something was missing, but everything is the same on both sides, and i checked my wife's bike, and her's is the same as well.

so what the heck is causeing the nut to loosen while i ride and what can i do about it? other then carry a socket wrench in my pocket everywhere i go?

i found a bike shop about 30 miles from where i live, so i'm gonna make a trip over there in the next few days, but i thought if anyone here might know what causes this, then i could at least get that taken care of.

thanks again.

[Kaiser]

Man, this is really bad news about the shop you bought it from and/or the bike's manufacturer. You really should have a shop look at it - you need to make sure the crank and bottom bracket are OK, that the BB is OK and sealed properly (if it was a sealed type) and that the crank is tightened back up with sufficient force (hard to do with standard tools). Barring having a home bike toolshop, you need to take it in, preferably to where you bought it. And complain... bitterly. This shouldn't happen under any circumstances. They should not only fix the bike, but be profusely apologetic and offer you free stuff or even the option to trade for a new (and better put together) bike.

Sorry that I don't have anything better to say, but the crank coming off on any bike, moreso a new one, is a big issue.

PS: Did you buy this at a bike shop or some other kind of store (e.g. dept store or sporting goods store)?

[FishrCutB8]

+1 to what Kaiser said...and if they balk, get your refund and walk.

[joshuaseu]

it was a bike shop, cycle source. i read some reviews on it and caught a few adds in newspapers and word of mouth from friends who were all happy with their experience, hopefully i just got a lemon bike. They own several stores around midwest and west coast i believe. everything i read was positive though, so, i'm kinda dissapointed. i'll give them a call and see what they say. they biggest prob for me is they are so stinkin far away.

thanks again

[silly]

Is it a Giant? We've had crank issues with certain Giant mountain bikes (Rincon and Yukon) this year. The LBS should take care of it for you. They come out of the box with the crank already, so it's easy to "forget" to check it during the build process. We fired a guy for being lazy about checking them.

[laxcdn]

A little loctite will help.