View Single Post
Old 03-14-07, 10:05 AM
Senior Member
closetbiker's Avatar
Join Date: Feb 2003
Location: Vancouver, BC
Posts: 9,630
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 24 Post(s)
Liked 18 Times in 6 Posts
Originally Posted by bigpedaler
... me, i'll stick w/ the tried & true.
by tried & true, you're not suggesting a regular 'ol bicycle helmet are you?

They've been tried and are true to prevent superficial injuries as long as the force isn't greater than 300gs' (a simple fall, little or no forward momentum) but getting hit on the helmet going over 20 kmh, it's not so true.

The BHSI has a page on the limitations of helmets

Bicycle helmets are designed as a compromise between impact management, cooling, weight, cost and many other factors...Under US standards bike helmets are tested in 2 meter drops that achieve about 14 miles per hour...Why so low, when bicyclists frequently exceed 14 mph in forward speed?...The typical bike crash involves a drop to the pavement...Although forward speed can contribute some additional energy...It is gravity that determines how fast your helmet closes with the pavement. Some of the crash energy is often "scrubbed off" by hitting first with other body The typical bicycle crash impact occurs at a force level equating to about...a falling speed of 10 MPH. The rider's forward speed before the crash may be considerably higher than that, but the speed of the head closing with the ground, plus a component of the forward speed, less any energy "scrubbed off" in other ways, normally average out at about 10 MPH.
So, it seems, as long as you have little forward movement (as in, not riding at a typical bicycling speed), and you manage to contact the ground with other body parts first, therefore slowing yourself down before your head manages to make contact with the ground (or other object), a helmet may be of some value. (but even that is under scrutiny if you read the cyclehelmets paper link) (you should also re-read post #1029 back on page 42 where it descibes case of a helmeted cyclist running into the side of a car at between 9-12 mph and having brain damage due to the "standards" of helmet design leaving the most vunerable areas of the skull unprotected)

If, however, you're riding along at a typical bicycling speed, (say, 30 kmh), some bozo in an SUV decides to make a quick left in front of you and you run into the bozo's rear quarter panel with your front wheel first, and your helmet second, I'd wonder how much good it'd do.

It sure isn't a 10mph fall with body parts "scubbing off" energy. It's twice the force directly into a hard object.

The experience (tried & true) in areas where there are large groups of cyclists wearing helmets show injury rates equal (or greater) to areas with little helmet wearing.

Maybe these types of collisions are why.

Last edited by closetbiker; 03-14-07 at 04:04 PM.
closetbiker is offline