How would you think that the BB bearing would have anything to do with the crank arm (not pedal) loosening? The problem is that once the crank arm is ridden loose it wears the square taper where it fits on the spindle, as the crank is aluminum and the BB spindle is steel. You need a new left crank arm, and then make sure both crank and are kept properly tightened.
Thank you for your opinion, I showed the bike to a bike shop clerk, and he thought that the crank is not in aluminium. so he said that that's probably not the issue here.
But somewhere there is an issue.
I thought it was the BB bearings because when I pedal, pushing on the left side the bike makes a "creacky" sound. and indeed the bearings I replaced were quite dented. Now with the new bearings the sound seems gone.
Given this do you still think I should replace the crank arm?
also: In your answer I think there was a word missing when you say:
"make sure both crank and are kept properly tightened".
I'm not sure needs to be tightened, crank and ...?
.. both crank ARMS are kept... Even steel arms can be damaged when ridden loose. Bearings have NOTHING to do with the crank arms. Either the crank or the spindle are worn, and the "mechanic" should have inspected the parts.
10-4 to what NY said. Examine the crank carefully see if it has any l/r play in it and if it turns smoothly. Take the arm off and examine the crank for wear than examine the arm hole. Any rounding will result in the arm loosening up . Make sure to tighten all well, but not as hard as you can, as you can strip threads.
Never Give Up!!!
Looseness from the bearings and looseness from the crank arm can feel the same to the untrained hand so it's not surprising you weren't sure which was causing the issues. You may very well have had both problems.
If tightening the black nut that holds the crank arm onto the bottom bracket spindle (axle) makes the looseness go away, then the problem is definitely not the bearings themselves.
The creaking you describe is also very typical of a damaged crank arm that keeps loosening up, so signs are all pointing to needing a new crank arm. However, just to be thorough...if the threads on the spindle or nut are damaged, it is possible you are never really getting this tight and that is why is loosens. But if you can take a wrench, crank that nut down solid and it doesn't feel stripped or anything, and the cranks still gets loose, probably a bad crank arm.
Note finally that if it is not loosening up now, but is still creaking, you might also remove the pedals, grease the threads, and reinstall them. That joint can make similar creaking sounds.
Hi I have this problem and I am 99% certain when replacingt he left crank arm I incorrectly threaded the crank bolt. This has resulted in the threads on the nut and spindle being worn.
My question is, what do I need to replace?
Do I need an entire crankset/chainset or can I get away with just a bottom bracket?
If the threads on the spindle are damaged enough then of course you will have to replace the spindle. If the crank arm has come off more than once the odds are very high that it must be replaced as well, even if that was not the original problem. Once you are replacing both spindle and arm it may be best to replace the whole crankset if the bike is worth it. If you replace only the spindle you must be careful to get a spindle/BB that is compatible with the type, taper and style of crank.
Thanks. Want to make sure I don't get ripped off. Someone suggested replacing the BB, crankset, rear crank and chain too, so as to ensure even wear.
Just get a new BB and crank arm, problem solved.
Already suggested, and again the OP needs to make sure to get a compatible BB/spindle.