So I was inspecting my Schwinn helmet that I bought from Wal-Mart, and I notice a small crack on the outside of it. I figure that this is a sign that its time to get a new helmet. But I'm wondering what is the difference between a $20 helmet from Wal-Mart compare to a $100 helmet I can buy from the local bike shop.

$80

Sorry, couldn't resist. On a more serious note, probably not that much, both meet standards, but I'm sure many will disagree. Fit and comfort could be the deciding factor.

https://helmets.org/testbycost.htm

Some helmets are certified for certain types of riding and have betting protection and padding. Other than that just fit and the name on the side of it.

The same $100 helmet you find at the bike shop can usually be found online a lot cheaper.

I ended up buying a Bell Piston Sport helment. The one thing I have notice is it says off Performance Bike's website that this helment is for city/suburban bicycling; is this still ok to use for mountain biking?

You can use almost any (certified) helmet for almost anything, almost.

After the certification for impact behavior, the big differences in different styles and prices is in ventilation, weight and coverage. MTB helmet tend to be better ventilated and have fewer zoomy looking projections than road helmets. My Limar has mesh in the vents to keep bugs out (I live in Florida, that's a thing).

I think there are some affordable MIPS helmets out there but I'm not sold yet on their effectiveness over ordinary helmets. If they really were that much better they would
be a household name by now, imho.

I agree. I don't know anyone that does not use the MIPS system or another variation. A helmet is a good investment. Don't cheap out on something that will protect your most valuable asset. I have had some had crashes and my helmet could have very well saved me from brain damage. Its like any protective equipment, make sure its fits good and feels solid. You don't have to buy a Troy Lee Design or a POC carbon helmet for 600$ or more, but honestly, the 100 to 200 for a half shell is a good range. If your going full face, anything under 200$, (in my opinion and not on sale) do not feel like quality helmets. That is my two cents.

Yeah the helmet I bought at my LBS is better quality than the Wal-Mart one, but the black color combine with the lack of ventilation holes make the helmet from the LBS something that is too unbearable in the summer heat

MIPS is of minimal effectiveness on standard bicycle half helmets, because they often do not fit real tight, and are able to move or spin a little anyway. On full face enduro and downhill style helmets that fit tighter it is more needed and more effective. On motorcycle and race car helmets, MIPS and the even more advanced ODS systems, it is something can can make a huge difference. Supercross racers started using the ODS helmets back in 2013. The heavier the helmet, and the tighter the fit, the more effective these systems are.

Here is a rider that probably should be using a full face helmet:
https://www.9news.com/article/sports...o/73-582377730

ouch

I've always found the cheaper helmets seemed a tad heavier with smaller vents and seemed hotter. I also have a large round head and the cheaper helmets just didn't seem to fit right. That being said I don't buy real expensive ones either, I try to stay under $100.

The last cheap helmet I had also fell apart, the shell was not glued to the foam very well.