Police tell M25 cyclist: It’s not a velodrome

73 Newtons in this planet's gravity is the equivalent of 7.44 kgf (kilogram force). Although kgf has largely been superseded by Newtons as a measure of force it is still used in China, by the European space agency and various other bodies. So no, not misremembering, not mischaracterising, and not research done by unqualified persons. https://www.forensicmed.co.uk/pathology/head-injury/skull-fracture/

One thing to keep in mind is that cracks in helmets are usually the result of tensile forces as the plastic foam is strong under compression, but weak under tension. It's possible that the crack formed due to the forces applied elsewhere e.g. if you snap a piece of spaghetti (or a Shimano crank), the break is not where you're holding it and applying force.

Yes. What a shitshow

[img]https://static.standard.co.uk/s3fs-public/thumbnails/image/2012/01/03/09/bald-squirrel-415x275.jpg[/img]

Dagnammit - have road.cc stopped the img tags from working?

"caused by a force as low as 10kgs" This sentence does not make much sense. Either you are misremembering or mischaracterising whatever research this was, or else this research you are quoting was done by people unqualified in this area.

Speak for yourself, why not [img]https://static.standard.co.uk/s3fs-public/thumbnails/image/2012/01/03/09/bald-squirrel-415x275.jpg[/img]

Well, they (medical professionals) almost always make "life-saving" claims about helmets though they're typically not that well versed in how bike helmets are designed to work (i.e. reducing acceleration by the foam compressing). Also, their view is skewed as they usually only see alive cyclists who've had a collision, so they're not in a good position to evaluate how effective helmets are. Again, the issue with bike helmets is not whether they do or do not provide some protection (they obviously do), but whether the cycling population is well served by focussing on PPE such as helmets instead of focussing on road traffic safety measures (e.g. increased enforcement of traffic laws, providing separate infrastructure etc). I mean, you never seem to hear of medical professionals stating how many lives have been saved by separated infrastructure even when stats across different countries suggest that they are much more effective in reducing the general danger level that cyclists face.

Genuine question, how much of that increased likelihood is attributable to the fact that less confident/ more nervous riders might be more likely to wear a helmet and also more likely to have a crash, and also to the fact that people are more likely to wear helmets in a perceived-risk environment? If all urban commuters wear helmets and nobody who rides on quiet country roads wears a helmet, obviously the urban commuters are going to be have more collisions and so the figures would show riders with helmets have more collisions but it would be primarily attributable to the environment, not the helmets. Is there any research that shows that amongst a cohort of riders of similar experience and ability, riding in the same type of environment, those wearing helmets will have more collisions?

They really aren't that tough, researchers have found that a simple skull fracture can be caused by a force as low as 10kgs; it has been known for people to fracture their skulls simply by walking into a door frame, and a very significant proportion of fractured skulls come from simple low-impact falls when walking. The idea that hair can protect you from abrasions is pretty risible, maybe if it was woven into a mat it might but on your head it's in individual strands; try running your fingernails over your scalp, does the hair protect you? No, it parts. Now imagine your fingernails are a rough road surface, the same thing would happen. None of this particularly is meant as a pro-helmet argument, but if you think you can rely on your skull and your hair to get you out of a crash undamaged I'm afraid you might well end up severely disappointed.