A bit of background, I run a climbing gym in the midwest and am a bald white guy.I received a call this morning asking about helmets that work well with dreads or with Afro textured hair. I of course want to be able to help any who calls but I was at a loss.I figure I would reach out to the people in the know and see if there is anyone out there in the community who could give any recommendations.
As someone with a head full of mixed curly hair I can offer my experience with helmets. The long and short of it: if you have a lot of high volume hair, helmets kinda suck and don't really fit correctly. I have to pull my hair back to wear a helmet correctly but the volume of hair usually pushes the back of the helmet up. If sized correctly and properly adjusted, I don't think this significantly affects the performance of the helmet but I have luckily not tested this theory so take it with a grain salt. The sizing and adjusting is very finicky if you have high volume hair.
When I have my hair braided (cornrows, etc) my helmet fits significantly better, so anyone with braided styles shouldn't have a lot of issues. Braid styles that have a lot of braids like box braids, it is better to distribute the braids with something like a buff or bandana instead of something like a hair tie, this way they are more spread out and interfere with the fit of the helmet less but are still contained and out of the way. The same advice should apply to large dreads, though a larger helmet may be required; I have never had that hairstyle so ymmv. Some kind of fabric between the helmet and hair is sometimes nice with kinky hair so the the inside of the helmet doesn't snag on hair (especially true with the mips inserts).