With a custom-built bike in somewhat higher price regions, I now ended up with a high-security u-lock, which is also very heavy-weight. I also own a heavy-weight chain lock. For several reasons and specific occasions, it would be more practical to carry these locks on my body instead of attaching them to the bike.

However, when thinking about accidents, and the corresponding forces of heavyweight metal, and the comparative weakness of my bones, I would at least like to know which variant of carrying the u-lock (like corresponding holsters, in - or attached to - a backpack, ...) or the chain (over one shoulder, or like a belt, ...) has the least "damage expectancy". My research, among others with the German Cyclist Club (ADFC), did not reveal anything specific ... apart from the obvious, that any lock will damage your bones less if attached to the frame.

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    I have not found any specific studies, but personally I prefer to attach things to the bike rather than put them on my person, for exactly this reason.
    – Criggie
    Jan 26 '20 at 9:49

To be honest, from time to time I am even afraid of the keys in my pocket, should they take some funny stance on a fall and happily pierce through my leg/waist. But that's not what you asked...

I would take a look from the other side: assuming that there will be a hit, where would it be less dangerous?

I would say that a metal object hitting your abdominal area is not going to be funny: too many things that can get damaged: spleen, liver, kidneys, ribs, pick one. So, take out holding it around your torso.

Arms and legs are less dangerous, if you accept a broken bone or a concussion.

Probably safer is a backpack: the most plausible scenario in which you will hit your back is on a flip over, and in that case I hope you wear a helmet. The backpack itself might soften the blow.

I once happened to flip over (a branch got stuck in my front wheel) and luckily my backpack went between my face and the ground. But I just had water and food in it, not a metal object.

  • In the past, I had to accept broken bones and concussions multiple times ;-), so I have a rough idea about these. Even though the abdominal area itself functions as a cushion, I see the point that the damage there can get much more serious...where "can get" probably means that if the impact energy is beyond a certain threshold. I suspect the energy necessary to break bones to be less than this threshold. So in case I ever learn to distribute impact energy during an accident accordingly, I would go for the abdominal cushion approach; until then, I'll stick with what you say! ;-)
    – StefG
    Jan 27 '20 at 7:32

I think one of the most common injuries is when your wheels lose traction and you crash-land on your side. This usually results in abrasions and bruises on your thigh. Having a lock (or keys) in a holster at your side is therefore a bad idea. It probably wouldn’t be life threatening but it could cause much more severe bruising or even broken bones in case of such a crash.

Falling on your back is less likely but obviously back injuries can be much worse. However, I think that a backpack containing a relatively “flat” U-Lock should be okay. You could add additional cushioning if you are concerned about parts of the U-Lock (e.g. lock body) protruding into your back. I have a Deuter Giga Bike bicycling backpack which has relatively thick cushioning and notebook compartment which is perfect for carrying a U-Lock.

I’m not sure about chains wrapped around your torso. How far do they hang down? Can they snag on anything? Do you really need the chain? Would a cable lock be sufficient? If you need it to secure your wheels, could you use Pitlock or other theft-“proof” skewers?

  • I agree some cushion is better than none. In addition to notebook compartments, I thought of air-cushion package material. However, combining heavyweight of the lock and higher speeds, in my slow-motion thought experiment, the air cushions just blow up and the damping of a notebook compartment is close to 0 compared to the impact. And you point me into the right direction with the chain issue; the closer these are wrapped around (hip, shoulder, whatever), less material is free to move and can build up an impact towards your body parts.
    – StefG
    Jan 27 '20 at 7:41

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