It was explained to me many years ago that the biggest difference is that bike helmets are designed to take one significant hit on one spot
The cost issue though is simply volume - lots less people race cars than ride bikes.
Nope - Snell rated SA and M helmets (Special Applications, aka Car, and Motorcycle) have to meet the same series of tests consisting of sustanining repeated impacts from a flat plate, a cylinder, a sphere, and a cone (point).
The SA helmet has to withstand an additional impact test simulating a Roll Bar (which shounds like another version of the cylinder impact).
The SA helmet has to meet a minimum flamability test (fireproof).
The M helmet has to meet a requirement for a larger "viewport".
Note that a helmet can meet both standards. A M helmet can have a fireproof liner, it can meet the "Roll Bar" test. An SA helmet can have a large viewport that exceeds the requirement for a M helmet.
And you are correct, the tests are very expensive and are spread over the number of helmets that are sold. Since many more M helmets are sold, they tend to be cheaper, and testing for both standards will increase the costs, and not really sell more helmets, so they tend to be certified to only one standard, even though they can often meet both standards.
Thanks guys for the info...guess I'm really asking, am I less safe wearing a car helmet while on the road on a bike? I'd rather get another car helmet if it is safe -
It all depends on the helmet. A SA helmet is not really safer than an M helmet, and as noted before, the SA helmet COLUD have a smaller viewport limiting you view that is necessary to see when driving a bike.
Aside from the nomex lining found in auto helmets, another difference is the wider viewing angle of motorcycle helmets. They allow more peripheral vision, necessary in everyday traffic situations.
Yep. That's probably the two biggest differences (keep in mind that a M helmet could have the fireproof lining, and the SA helmet could have a big viewport.
As Tom and xtn mention there is a viewing port issue of a car helmet on a bike - but the bigger issue (here in Australia anyway) is that car helmets are not certified for bike use. So despite being as good or better unless your helmet is certified for its intended use you run a legal risk but probably not a safety risk (stupid - I agree
). Is this a big issue for you
- perhaps not - but it is best to be informed
Probably not an issue in the US - usually states only require that a helmet meet DOT standards, not Snell, and you could probably meet DOT standards with a construction site hardhat.
...when i visited the simpson factory, the particular helmet model i wanted was available with either an SA or M rating, yet it was literally the same helmet either way - they fitted me with an unstickered helmet off the factory line, then based upon which model i wanted, carried it back and affixed it with the appropriate sticker...
...now i'm sure that's not the case with every helmet - the SMF website notes that SA helmets require an additional flammability test, M helmets require a wider field of view, and SA and K helmets require an additional multi-impact test - but it's entirely possible for a single helmet to meet all three standards, with the sticker differences only being due to licensing...regardless, all SA helmets will meet K standards, some SA and K helmets will meet M standards, and some M helmets will meet K standards, but few M and K helmets will meet SA standards...
Yep. But any specific helmet MAY meet any/all of the standards, but not be tested to the standards.
Yep. The whole Snell testing proceedure is there - it describes the tests in detail. Most of the standards for the different certifications differ in only a couple of the details (like the extra "Roll Bar" test, etc.).