alessandro!

Hey there!

I just wanted to know what these bolts are for and why do they have such a special locking mechanism? https://biketools.co.uk/product/4/954...t-And-Cap.html
I have a very similar one from campy on my Bike (with two holes aswell), and the cranks are going loose all the time. Could this be related to not having locked the bolt properly? What tool do I need to achieve this? I have a similar system with my Bottom Bracket, but the holes are bigger...

Thank you very much for any help!
Alessandro

Jeff Wills

The two-hole end cap is there so that (in theory) the bolts can be used to remove the cranks. They have nothing to do with cranks coming loose by themselves.

If your cranks are loosening, then you're probably not tightening them enough. They should be tightened to roughly 30 lb-ft (40Nm). That's a lot of torque for a small hex wrench, more than most people can apply by hand.

Unfortunately, if you're ridden with the cranks loose, the holes in the cranks may have gotten distorted to the point that the cranks will never tighten properly. You'll have to replace the cranks in this case.

lverhagen

Those bolts are referred to as the one-key system, a crank extractor built into the crank bolt and dust cap assembly as Jeff Wills stated above. In order to tighten the outer ring you need a pin spanner like this: https://www.parktool.com/products/det...t=4&item=SPA-2

Cheers

Bianchigirll 

but as Prof Bunzen points out the single key release if installed correctly should not be causing his crank to come loose.

the OP needs to remove his cranks, clean the spindle and the crank then reinstall and torque.

Never ride a bike with loose cranks. they can be easily damaged.