Locktite 648 and crank arms

[Spankyfart]

I have crank arms coming loose on tapered cranks used on a tongshen mid motor (known issue).
Obviously the locking bolt needs it, do I put drops on the tapered part too?

thanks,

 

[Spankyfart]

Yes it's on a pre '97 MTB.

 

[bikeworkshop]

If the cranks are loosening, the alloy tapers are opened up and threadlock is unlikely to stop future failure.

Tightening every day, or replacing the crank (usually LH, rarely both but electric power brings new Failure modes to bicycles) is probably the only way to avoid a stranding

 

[Spankyfart]

Yeah it's a common issue with these tapers on the tongsheng.
So I only use it inside the thread then?

 

[bikeworkshop]

Because you'll probably need to retighten as the tapers stretch, any threadlock is likely counterproductive.

It might mean it takes a few more miles for the crank to loosen, but it won't stop it.