Why do you want to wear a dirt style helmet. I am assuming you mean a motocross helmet? If so let me tell you from experience; motocross helmets are not designed for highway speeds. I'm not talking about strength (although the jury would have to make a judgment on that because you can get DOT motocross helmets) but I'm talking about aerodynamics. I've worn motocross helmets while on my "true" dual sports and the runs on pavement at highway speeds are a pain. The wind catches the visor and chin bar much more than on a street helmet. I will say however, if you are riding a lot of gravel roads the motocross helmet has an advantage because you wear goggles that seal to your face and the goggles keep the dust out of your eyes. Some companies are making a hybrid helmet for super moto that look interesting because they have a smaller visor and are more aerodynamic but most of them use a flip up visor rather than goggles so I see no advantage over a street helmet.
To sum it up, IMO; for mostly street with a little gravel road ~ stay with a street helmet. For mostly gravel roads with a little pavement in between ~ a motocross helmet works but even then, I've gone to using a street helmet. I only use a motocross helmet when I haul the bikes to a purely off road area where I stay off the pavement (and of course that doesn't involve the V).
'09 Versys in Cool Lime ~ '06 Harley Roadking
'95 Suzuki DR350S ~ '94 Suzuki DR350S
'09 Kawi STX15F jet ski ~ '07 Kawi STX12F Jetski
'09 Yamaha Superjet ~ '13 Ram 4X4 3500 Cummins
'09 BMW 535i ~ '10 Kubota B3300SU
Last edited by DennisD; 05-13-2010 at 08:34 AM.