Bicycle Helmets and Do-Rags
Summary: Caps or do-rags worn under helmets can affect fit, but are ok to use as long as the helmet fits well with the
cap in place.
Various manufacturers are selling do-rags (a cloth that goes on the head) to fit under helmets for either sun protection
in the summer or heat retention in winter.
Putting a thin cloth beneath your helmet raises some questions. Is fit affected? Is your head now more slippery, letting
the helmet slide around in a crash or even flip off?
Bald riders will realize that a cotton cloth or sunscreen cover on your head is not as slippery as skin with sweat and
suntan oil on it. In addition, those who use a cover on their heads in summer to avoid funny tan lines usually fold the
cloth so that it does not continue down the sides, where it would come between the fitting foam and the head. (We have
more on our
bald rider page.)
What about those with hair? We are not sure. The cloth could possibly make your head more slippery than hair, even hair
with sweat and oil on it. But the real work of keeping the helmet on your head is done by the straps, not the friction
between fitting foam and the head. We believe that if the straps are not adjusted correctly, the helmet will be less
likely to stay on, no matter what the surface of the head is like.
If you think about how head covers might influence the grip between helmet and head, it would seem that some of what a
do-rag does is to increase the size of the head a little bit, squishing the fitting foam just a little more and raising
the helmet just a bit, putting a tiny bit more pressure on the chin strap. That is assuming people don't readjust
anything unless the head covering is really thick. Balance that against whatever effect the do-rag may have on the
friction between helmet and head, and the effect is likely to be small. Although we have no good way of testing this
hypothesis scientifically, that would seem to indicate that do-rags will probably not make the helmet more likely to come
off in a crash. Some have tried it with the rolloff test in the ASTM and CPSC standards, and have found no effect. But
that test is too crude to provide a good indicator.
If you use a do-rag in summer or a winter cap under your helmet, you can help. Put your helmet on with and without the
cloth, and try to tear it off. Let us know
with an email if you detect a real difference.
Our best guess is that do-rags are probably ok for most riders if the helmet is properly adjusted with the cap or cover
in place and passes the
tests for a well fitted helmet.