Bolts becoming loose

[Everett]

I have a motobecane fantom cx with a rear pannier rack. Just like one that is off of bikesdirect.com to give you an Idea. well to get to the point. Bolts have been backing out! not only with my Pannier rack but also with my crank on the nondrive side. It just falls off and I have to keep tightening the bolt everyday or so. Have any advice to keep them from doing this?

[DaveM]

On the crank bolt, this may mean that the crank itself is damaged (is it a square taper fitting?). If so, only real fix is a new crank arm.

On the rack, you can try locktight and/or lock washers. Stronger solution is bolts that are long enough that they go through the frame and leave enough thread on the other side for a nut (preferably a nylock nut).

[Everett]

(10-07-2012, 05:52 AM)DaveM Wrote:  On the crank bolt, this may mean that the crank itself is damaged (is it a square taper fitting?). If so, only real fix is a new crank arm.

On the rack, you can try locktight and/or lock washers. Stronger solution is bolts that are long enough that they go through the frame and leave enough thread on the other side for a nut (preferably a nylock nut).

NO!!!! it is a square taper fitting.. what would have caused it? bottom bracket? and would I need a new bottom bracket as well?

[RobAR]

Everett. It's doubtful that your bottom bracket spindle is damaged. Most likely your (aluminum) crankarm simply got too loose and deformed at the interface. It will never stay tight now.
I hate to say it but, what caused it was you and lack of preventative maintenance. Rack bolts, too. On a regular basis, a cyclist should go over every fitting on a bike from top to bottom and check them.

[Bill]

Along with Dave was trying to say If the bolt or nut keeps backing out/off then the threads in the spindle or the bolt/nut worn out! Easy fix as some could understand get yourself a new Bottom Bracket and crank arm!