My posts are mostly from the viewpoint of a relative newcomer to biking; this is my 2nd year and I'm still discovering the stuff that is old hat to most of you, so old hat that you don't say it because everyone knows it. Not everyone as it happens. I'm sure there is a percentage of the people here who, like me, are relatively new to the sport. I doubt that I have any insights of interest to someone who has been biking for decades but most of my observations represent hard won knowledge to me and possibly of interest to someone just entering the sport. So please take my infantile observations in that light.
Helmets: Didn't really have the problem last year because I didn't wear a helmet last year during the summer, just a head band and ball cap. That plus the fact that my rides a year ago now were at about 13 mph average and around 1-1/2 hours max kept the potential problem to a minimum. Fast forward a year and I'm now wearing a helmet, riding 5+ mph faster and for 2 to 2-1/2 hours a day in Florida and helmet cooling has become a major thing.
My previous helmet is a $25 "big box" effort by Pacific Cycle. From a protection standpoint, it is probably as effective as anything in common use today. The head size adjustment mechanism and straps are at least as good as as the much more expensive helmets that I now have. What it doesn't have is cooling slot area or internal connections between the slots. But it worked well for my daily rides through the winter down here (such as it is) and spring. The past couple of months have shown the limitations because I've not been able to complete a ride without coming out of the helmet.
A couple of weeks back, I bought via the internet a Bell Influx, a mid-grade helmet (average sales price $60) and with a common review comment saying how well it cooled. I ordered it medium because Bell's site stated my measured head size was smack in the middle of medium, but it wasn't even close, I couldn't wear it at all. I needed large, the charts are wrong.
I noticed that the Bell Influx had a massive increase in the total area of the helmet that was open for air slots, maybe as much as approaching double the open area as with my "cheap" helmet. I also noticed that the internal surface of the Influx was flat, just like the "cheap" helmet. I never rode with the helmet.
When reordering the helmet, I noticed that they had a deep discount special on Bell Volt helmets which usually sell for in the $175 range, deep enough to bring it down almost to the Influx range. So a large Bell Volt is what I ordered. On observation, the Volt has the same adjustment mech and very close to the same percentage of slot area as the Influx. Construction, shape, materials seem identical. The only real difference I could find is that the interior surface of the Volt is sculpted so that there are channels interconnecting the exterior slots. Is that plain? I'll photo the helmet interiors later to illustrate. Rode with the Volt for the first time yesterday and for the 1st time in my helmet wearing life, felt air flow across my head while wearing a helmet.
Yesterday did the Volt helmet make me feel like I was riding in air conditioned comfort? Not even close. But what was different was that I kept the helmet on for the ride. The best a helmet can do in hot conditions is give you impact protection while allowing the most cooling possible with a theoretical maximum of no helmet at all.
I have to question the pricing. Like I said, I could find no difference between the Volt and Influx except the air passages between the slots in the molded styrofoam. Is that worth $100?