Advocacy & Safety - Any Mountain/Ice/Rock Climbers?

Well, I don't have a helmet yet. I am still in the process of repairing my bike, so haven't ridden for a month or so. This morning, it occurred to me that these "climbing helmets" might be better for bicycling, since doing a swan dive headfirst into a rock wall is probably something a climber might have to do if he loses his grip and falls. However, I'm not a climber and don't know any climbers.

Anybody out there have any knowledge about these helmets?

As you can see from the following link, the climbing helmets seem to cost two or three times as much as a bike helmet.
http://www.rei.com/category/4500689

I have a large head. Seldom does the local bikeshop have a helmet big enough to fit my head. So I'll probably order a helmet. Should I order one of these "climbing helmets" or stick to the cheaper bike helmet?

They are designed for different impacts. Rock climbing helmets are mostly their to help against hitting your head on sharp rocks, or getting hit by falling rocks. So for that fact, they have a hard shell that distributes the force across your head, and a denser foam that won't crush from getting banged around a bit. They also aren't very aerodynamic or designed to ventilate in a wind flow like on a bicycle.

Bicycle helmets are designed to absorb energy from a crash, the outer skin is very thin and doesn't do much. When you hit concrete, the foam is suppose to compress, decreasing the acceleration of your head as it comes to a stop.

some of the Born helmets are multi-sport, but you're really much better off in a sport specific lid.

all the climbing helmets I've owned are not microshell but a hardshell over a webbing suspension, distinctly NOT suitable for cycling. the petzl ecrin roc is an iconic climbing helmet, but not useful/safe for biking.

It's already been said, but being a climber, I feel like I should nose in and repeat what everyone else has already said. Climbing helmets are designed for falling sharp thingies, not for falling off a rock and onto your noggin. They are not suitable as a replacement cycling helmet.

I also think the ventilation is better with a bike helmet. Climbing helmets don't have holes in the right spots for forward progress airflow. You don't want holes in the TOP of a climbing helmet due to falling rock pieces.

Thank you all for taking time to explain this to me. I am glad to hear you recommend the cheaper helmet for biking.