I need a lid and have been looking around - of course fit is priority #1, but what makes a road-specific helmet so unique? What, if any, would be the disadvantages of using a MTB-specific helmet for tri?
I have found a few that I really like the fit & aethetics, but some of them are claim to be for off-road, like the Giro Exodus that I'm leaning towards.
It's not like I know a whole lot about helmets, but the only real difference I see is that MTB helmets have the little visor. I've used one of those for all my tris and if it ever gets to be a performance limiter, well ... look for me on the Olympic podium. What difference could it possibly make??
I have an MTB helmet that used to have a little visor until I recently removed it. I just bought my first road bike and because of my position on the bike, the little visor blocks my view of the road. Taking the visor off now lets me see where I'm going.
MTB helmets have the "little visor" because when your on your MTB you are going slower than on your road bike and the "little visor" assists in airflow through your helmet at the lower speeds. It's removeable in case you want to use the same helmet on your road bike and don't need the airflow assistance and want more aerodynamics.
I have 2 MTB helmets, and one of them I use for road and tris as well (the other is a full face MTB helmet ). I've tried riding on the road without the little visor, and can't. I've found that it blocks a lot of the sun and keeps the glare down while riding in sunny AZ, which allows me to see better. And I've gotten used to it. I've had no problems with the visor at higher speeds, so I just leave it on.