What is the big difference between helmets marketed for road biking vs helmets for mountain biking? Does it really matter?

If you do a search this was asked like 2 days ago...no diff...same safety features...road bikes just make people look like pylons and xc helmets look like...well ventilated pylons (can you tell I hate helmets..I wear but think non full faced are ugly..)

In theory, Road helmets are designed to give maximum airflow at higher speeds, and MTB helmets, maximum airflow at slower speeds (hence, the larger vents...) Pro's tend to wear Road Racing Helmets though, because they are lighter (and they don't have to pay for them - they're expensive).

Mike

Visors...seems like most MTB helmets have them whereas Roadie Helmets don't...

Off-Road helmets have more mass, bigger vents, visors and some provide a little more head coverage than their road-specific cousins.

I think the next helmet i will buy will be road helmets. They're much sleeker and seem to conform to the shape of your head. When i wear my helmet i feel as if the helmet is sitting so high off my head and it makes me look and feel goofy (not that i mind considering i feel a lot safer bombing down a rocky hill).

If money wasn't the issue, my personal choice would be the Louis Garneu (sp?) Aki V, which I think is a road helmet, but I only have an mountain bike.

Giro just put out their pnumeo with little mounts for a visor but it didn’t come with one. weird.
I can tell you a distinct difference between the Pnumeo (road) and the E2 (mtb.)
The Pnumeo is built to maximize airflow in a more head down position as the vents in the back of the helmet are slotted vertically for force air down when in an aero position.
The E2 is vented for a more "heads up" position.
But i know people who use both for both and don’t really have any problems.

is Giro Eclipse any good? Does anybody own one?
they can be had for cheap on ebay

I think Toninator maybe on to something about the slot design difference between the road Pneumo and MTB E2 designs. As for the Eclipse, I think this was Giro's top-of-the-line before the advent of the Pneumo a couple years back. I'd think the protection, styling, fit and venting is consequently second only to the Pneumo. The RocLoc retention system, for example, I believe is type 3 on the Eclipse but the newer type 4 on the Pneumo. BTW I wear an E2 with RocLoc3 and it's a fine product.

I have an Eclispe and love it. But then, it's my first "good" helmet, so maybe I don't know any better But I do love it. I hardly know i'm wearing it. I actually have to touch it to make sure sometimes.

Anyone know the difference between RocLoc3 and 4?

What is a good helmet to get and where is a good internet site to get one at? I don't really need to spend very much, just would like a descent helmet.

Thanks