Re: Roll Bar vs. Harness Bar

[Jim Ochi <jochi@xxxxxxxxxxxx>]

KKASPER4@domain.elided asks:
>
>I am currently planning on increasing my track time in my '96 M3, and I have 
>decided to invest in safety improvements before further performance 
>modifications.  I plan on using my car a fair amount on the street as well
as 
>on the track, and would still like a functional backseat.  At a recent 
>driving event at Seattle Int. Raceway I noticed a number of cars with
harness 
>bars.  From what I can tell, the obvious advantage of the harness bar is the 
>ability to remove it and return the car to a stock look.  My concern is
being 
>harnessed upright in my seat in the event of a roll-over.  A roll bar would 
>obviously be the best option in that situation, but my concern with the roll 
>bar is what the effect would be on non-helmeted passengers (both front and 
>back seat) in the event of an accident on the street.  I would appreciate 
>advice from anybody who has had experiences with these devices.
>

Thomas - 

First of all, consider a harness bar as a convenience item more than a
safety device.  It makes it more convenient to mount your shoulder
harnesses, and allows you to remove everything on the street.  The only
safety function that a harness bar provides is that it mounts the shoulder
harnesses at the correct height, helping to prevent spinal compression in a
crash.  

A roll bar is a safety device, adding more structure around the driver in
case of a crash.  However, if you install one, give up on the idea that
your back seat is still functional for hauling passengers - don't even
consider it.  Too much metal too near people's heads to be safe.  And,
don't fool yourself with the idea that adding roll bar padding will make it
safe - it's still not enough to protect a non-helmeted head.  Just think of
the pre-airbag days, when the government mandated padded dashboards -
people still sustained skull fractures from the padding bottoming out on
the steel structure of the dash.  

Both of these devices also tend to make the car more dangerous, if you
don't install racing seats with a back brace - if the stock seat recliner
collapses in a crash, the harness bar or the cross brace on the roll bar
will be right there to take your head off.  But, if you install racing
seats with a seat back brace, you won't be able to easily adjust the seat
for multiple drivers, and getting in and out is more difficult.  Once
again, you have a tradeoff between safety and utility.

Welcome to the dilemma of trying to make a dual-purpose car!  If you do
what's good for street use (i.e. put in the harness bar), it increases your
risk at the track by making rollovers more dangerous.  If you do what's
safest for the track, it decreases the utility of your car on the street by
eliminating the back seat for passengers.  Unfortunately, there's no easy
answer - you need to decide how much risk you're comfortable with vs. how
much utility you're willing to give up.

For me, the answer was a bit easier - I primarily autocross, where the risk
of rollover or collision is low.  The car I use is my daily driver, so
giving up the backseat for passengers is not an option, which ruled out the
roll bar.  So, I got the harness bar.  If I did more track events, I would
probably reconsider.  At that time, I'd also think about getting another
car to use solely for track events, mainly because if the risk of crashing
is that high, I wouldn't want to put my daily driver at risk.

Sorry I can't be of any real help...

Jim Ochi
jochi@domain.elided

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