My lbs changed the chain and the front bracket. Now I have an issue with the right crank arm because it keeps getting loose, no matter how tight it is.
I sent the same video to my lbs and he told me that I need to tighten it really hard ( which I did since the first time, otherwise he will tighten it for me). Since I like him and didn't want to create pointless arguments I didn't answer yet, but I did tighten it to the point where I could feel that if I went any further there was a serious possibility to strip the bolt.
I somehow doubt that he will be able to. I noticed that the black plastic ring is missing from the loose crank arm, maybe it's the absence of that piece that makes the bolt unscrew itself? It is present on the other side
Loose bolt on the crank arm that unscrews itself after 3km
byu/StandProud94 inbikewrench
by StandProud94
4 Comments
Unfortunately you need a new crank arm and potentially a new bottom bracket.
If it’s been tightened a few times and come loose, and been ridden lose at any point you’ll have rounded the square hole on the arm, and maybe the square axle on the BB
You can tighten it again and again and nothing will fix it until you replace the arm, and the sooner the better. If you keep riding you’ll need to replace both
The LBS that didn’t spot this isn’t a good one or you were speaking to a super junior. This is super common and they should have clocked it
Bring it back to your lbs. He needs to fix it if he worked on the bike before. Chances are that the loose bolt allowed play on the crank that rounded out the Square taper of the crank.
That crank is rounded now. It will always come loose. So that’s a new crank arm.
Replace the crank, you should be fine.