My left helmet strap keeps vibrating and flapping while I do fast descents... any way to fix this? I've already tightened the helmet as much as possible..

Can you take a picture? It will be easier to understand the problem and help you fix it..

 

Bah ha ha.

 

Strap between the buckle and the helmet, or strap downstream of the buckle? If the latter, cut it. If the former, try sunglasses outside the straps, re-adjusting the strap throughout the helmet, or it's possibly a fit issue.

 

Do you wear your glasses over the straps? That could help.

 

Sometimes they just flap. The straps on my Specialized Prevail are a bit further away from my head than my previous Giro helmet, and they will vibrate. Depending on which of two sunglasses I have I'm wearing I either put them on the outside of the strap to hold the straps in... or the other pair goes inside the strap to keep them taut.

 

Move some place flat as a pancake.

 

flat places have very windy days.

 

Do the twist. Put a twist in the strap that flaps. You might have to unthread the strap from the buckle and rethread it but if you do this you will not only stop the flapping but you will reduce the wind noise.

 

MUST, FIGHT, OCD, TWIST STRAP....UGH, cannot twist my straps, it just doesn't feel right. Although, I'm sure it works. I'm glad I don't have this issue with my helmet.

 

I stand corrected.

 

I am suffering with the same issue in my helmet but I thought it is because of our head size. And to solve this problem I am using a second option.

 

Grow a beard.

 

Have you tried using a large "C" clamp?