Stupid question about helmets

So my old autocross/track day helmet has expired. I'm currently lining up gear for both Lemons/Chumpcar as well as for tooling around on my recent motorcycle acquisition.  It's a fair bit of coin. Clearly I'm going to want a helmet that meets the car racing spec. My question is whether that'd be a decent choice for the motorcycle as well, or whether there's another consideration I should factor in RE: the bike helmet? 

Thanks!

I would not use a car helmet on a bike.  Just the wind noise alone would probably drive you nuts.  The testing is also different.  Some events/santioning bodies allow motorcycle helmets at car events.  I've always used my bike helmet for autocross, open track, and Track Night in America but I think if you go up to like Time Trials or Optima events it specifically states motorcycle helmets are not allowed.  Check the rules for the specific events that you're going to run and see what it says.  I'm in the same boat right now.  I just bought a new Shoei RF1200 to replace my 8 year old Shoei RF1200 but I'm still going to have to buy a car specific helmet for some events I want to do.  It sucks but nobody ever said racing was cheap.

I have a very nice size L Shoei GT Air sitting in a closet, if it fits your head. I only wore it once or twice before I sold my bike.

LeMons, Chump, and most every HPDE group will require you to have a Snell SA helmet (maybe FIA will pass, that's probably up to their insurance) but a Snell M helmet will fail tech.

Likewise, if you're riding a bike, There's some evidence that the Snell safety standard is junk, and you're safer in an ECE helmet. An FIM rated helmet would be the holy grail for safety on a bike, but that's both new and expensive.

You can spend all your money on helmets, and if you wear them enough, that's probably money well spent. I personally wouldn't spend less than about $300 on a lid, but I spend an awful lot of time in them as an HPDE instructor and a motorcyclist.

Money spent does not equal increased safety. Higher cost is usually a function of features and construction materials. Getting one that fits properly is way, way more important.

The way it was described in the old days was M rating is for one big curb impact, SA rating is for multiple smaller hits on a roll cage.  I would use a motorcycle rated for motorcycling.

SA rated helmets have additional fireproofing and tend to have smaller eyeports than M rated helmets, as well.

ddavidv said:

Money spent does not equal increased safety. Higher cost is usually a function of features and construction materials. Getting one that fits properly is way, way more important.

I wish I had included this in my initial post. Increased cost usually correlates with more features/comfort. Replaceable pads can give you a couple extra years out of a helmet, and all things being equal, the lightest helmet will strain your neck less with G force (in a turn or an impact). Doesn't do you much good if it's too loose though.

The motorcycle industry has figured out how to list head shape with each model, I wish SA helmets would catch up.

glueguy (Forum Supporter) said:

The way it was described in the old days was M rating is for one big curb impact, SA rating is for multiple smaller hits on a roll cage.  I would use a motorcycle rated for motorcycling.

More or less this. The helmets are designed for very different purposes and scenarios. One big example is a car racing helmet likely has built in provisions for head/neck restraint devices. 

There are a good bit of S.A. helmets with large eyeports and wind deflectors to keep your head steady while racing an open wheel car.  

I would see no reason an S.A.helmet wouldn't work on a motorcycle.

Maybe look into what the differences are according to the M or S.A. rating.

wvumtnbkr said:

I would see no reason an S.A.helmet wouldn't work on a motorcycle.

Most SA helmets do not have a US DOT helmet certification (presumably due to cost) and are therefore not legal to use while riding a motorcycle on the street in many states.

Functionally speaking I suspect it would be fine though.