HELMETS 101 - Hope this might be helpful for someone:

So you're interested in doing Rallycross or Autocross(Solo II)? You need to get yourself a helmet. You'll probably race with SCCA (Sports Car Club of America). They require you to have a helmet that meets safety standards. I'll get to the specifics later.

-FYI-

Most Common Helmets:
Full Face Helmets Flip-up or Modular Helmets
Open Face Helmets Half Helmets - Never Snell approved, only DOT

Full Face and Open Face helmets are allowed in auto racing. Modular helmets are allowed as long as they lock shut and are Snell approved.

In motorsports an open faced helmet is preferred for easier breathing, keeping cool, and more room for intercom set up. It's safe enough because the harness keeps you from bashing your teeth into the steering wheel. This is Patrick Richard with his open face helmet. You can see his intercom set up.



-SAFETY TESTING-

There are two safety testing organizations: DOT (Department of Transportation) and The Snell Memorial Foundation. Helmets that are DOT approved are street legal but meet only minimum requirements. Snell came about after a tragic accident which could have been avoided if the crash tests on new helmets were kept up-to-date and had higher standards. DOT testing has not been updated since 1972. Snell is updated every 5 years and keeps strict tabs on which helmets get the approval stickers and which do not. The Snell approval sticker is located on the inside of the helmet behind the lining.

DOT automatically issues approval stickers without testing. They have undercover shoppers go to the store, buy one, bring it to the lab, then if it fails the stress tests they take away the producers right to put a DOT sticker on it. Many are sold before the DOT sticker is recalled. Snell tests before the helmets are put on the market.
For an example of how strict they are, if a Modular helmet has plastic mechanics to lift the shield it will not be approved, they have to be metal.
Snell Testing:
Rocks and bugs like a speeding bullet!



The SCCA national rules for Autocross(SoloII) and Rallycross state that the following are allowed for competition:

Snell 90 “SA” or “M” labeled helmets are approved for use.
Snell SA 1995 or newer will replace this standard on 1/1/06.
This is a minimum standard for use in RallyCross, other approved helmets are:
1. British Standards: BS 6658-85 type A/FR, including all amendments.
2. SFI Foundation, Inc.: SFI Foundation, Inc.: SFI Spec 31.1

Snell 90 was last updated in 1990, then they updated in 1995, now in 2000. So technically Snell 2000 is the best helmet you can get although for AutoX and RallyX Snell 90 is good enough (because you don't really go THAT fast).

What you should know about the difference between autocross helmets and motorcycle helmets:

Snell's SA2000 Helmet Standard was designed for auto racing helmets. The M2000 standard is used for motorcycling and other motor sports. There are three major differences between the standards:

1. SA2000 helmets require a flammability test while the M2000 helmets do not

2. SA2000 helmets allow for a narrower visual field than the M2000 helmet standard. This may make some SA 2000 helmets illegal for use on the street. (I personally disagree, they are pretty standard)

3. SA2000 helmet standard requires roll bar impact test while M2000 helmets do not.

To be more specific, Snell M2000 is designed to take more impact in the forehead for when you fly off your motorcycle face first, whereas, Snell SA2000 is made for impact in the back of your head when you slam back against your roll cage.




Now lets talk about getting one!

When you're looking for a helmet, consider these things:

Safety Standard - Now you know all about it! Make sure it's Snell 2000 or higher!
Visibility - Can you see right and left out of the corner of your eyes? They should be standard, but sometimes slightly different.
Weight - No joke, those buggers get heavy and will give you neck pain.
Ventilation - For motorcycle helmets especially, flow-thru vents are very helpful for keeping your head from sweating AND making you dizzy.
Quick Release - D-rings are hard to undo when you have gloves on so consider getting a quick release chin strap.
Fit - VERY important. Not too small, not too big.. read on..
Price - Should be your lowest priority, but sometimes you're paying for the brand name. You can have a perfectly effective helmet for less money.

-WEIGHT-

To be more specific....
The weight of your helmet will affect you dramatically. If it's too heavy it will fatigue your neck and delay your reaction time when looking side to side. It's especially uncomfortable when riding a sport bike because you are leaning on your gas tank and trying to keep your head up.

Shoei and Arai helmets are known for being exceptionally light. Fulmer helmets are also light weight and a good brand for a lower cost.

The lightest helmets will be about 2 lbs. 13oz and a helmet on the heavier side would be about 4 lbs. 1oz. Check the weight of a helmet before you buy it! I speak from experience!

-FIT-

When you put the helmet on it should be snug on your forehead. Do this test:

Look forward and try to keep your head facing forward. Jerk the helmet side to side and then up and down. If the skin on your brow moves with the helmet then it's the correct fit. If the helmet slides around then it's too big. A helmet that does not fit correctly can sometimes do more damage than not having one. It can create double whiplash or double impact. As in, first the helmet will hit the pavement or rollbar then your head will hit inside the helmet.

Check for proper fit - is it tighter on the cheeks than the temple or vise versa? Different brands have different fits so try them all. It should fit pretty tight and consider that you will break it in and the foam will contract a bit.

Ok, just some advice.. If your helmet fits so snug that you start passing out, then you should probably get a bigger size. Also, if it is so tight on your cheeks that it starts unhinging your jaw, also get a bigger size - ouch!

-$$$-

Prices range from $69-$900.
M series, open face helmets are the cheapest. You can use them for your motorcycle and for auto/rallycross. They run about $69+
M series, closed face helmets will be about $79+
SA series, open face helmets will be about $150+
SA series, closed face helmets are about $190+

I'll paraphrase what Evil Knievel said: "$10 heads deserve $10 helmets!"