Useless Rollbars?

August 21, 2005 5:54 PM

I have a question that has been nagging me a bit to ask. You know the rollbars on convertibles - like the ones on the Porsche Boxter, Audi TT, Mazda Miata, BMW 3-Series convertible "pop-up" rollbars, etc. If you are a tall person (say over 6'3") and your head is higher than the rollbar when sitting upright wouldn't it likewise be higher when you are rolling over (at least at some point during the roll), thereby rendering them useless for tall people?
posted by gnash to travel & transportation (12 comments total)

Yeah, but it'll still save your ass. Instead of having the entire car come crushing down on you, you'll only get your head banged around without the car coming down on you.

(So says this 6'3" BMW driver...)
posted by NotMyselfRightNow at 6:06 PM on August 21, 2005

Yes, the top of your head will get hit, but it won't be forced down to your navel like it could with no roll bar.
posted by Kirth Gerson at 6:11 PM on August 21, 2005

If you want to race a Boxster, the top of your helmet must be under an imaginary line between the rollbar and the top of the windshield (which is actually the front rollbar). They check this with a broomstick.

If you're over, it's considered unsafe, and no racing for you.
posted by mosch at 6:25 PM on August 21, 2005

Yeah, you'd be a hurting unit. Roll bars and such are based around some assumed driver size. Putting roll bars that would fit a 7'6" guy would ruin the look of most of those cars while not really increasing sales (and probably reducing them).

It's sort of like buying any car, not all cars fit all people.
posted by substrate at 6:55 PM on August 21, 2005

Wouldn't the tall driver duck?
posted by pompomtom at 7:01 PM on August 21, 2005

"Wouldn't the tall driver duck?"

Wouldn't do you a lot of good in a high-G rollover.
posted by mr_crash_davis at 7:03 PM on August 21, 2005

It seems to me that while there's little or no slack for forwards movement in auto-tensioned seatbelts, you would wobble quite a bit in the wrong direction if your car was upside down, so losing your brainpan would be an issue for many tallish people in a convertible.
posted by wilful at 7:34 PM on August 21, 2005

They are not totally useless for tall people. They will still reliably protect the lower 95% of your body.

But seriously,

If you own the car, and you like high performance driving, you might consider a mod.
posted by Ken McE at 7:40 PM on August 21, 2005

In normal, not-flipping-over driving conditions, having some sort of protrusion like a roll-bar helps keep the wind noise down. Some convertibles have a little 'rear window' behind the roll bars that is designed explicitly to do this.
posted by blasdelf at 9:11 PM on August 21, 2005

You know the rollbars on convertibles - like the ones on the Porsche Boxter, Audi TT, Mazda Miata, BMW 3-Series convertible "pop-up" rollbars

The "roll bars" in most cars are actually style bars, and while they do aid in stiffening the body and reducing flex, offer no protection in the event of a rollover. Real roll bars have at least three connection points, but usually four, welded to the floor, with diagonal bars behind the passangers and a minimum of 2" steel tubing. (This doesn't include the innovative BMW system).

The A-pillars of all convertibles are reinforced, and undergo tests for safety whereby the car is rested upsidedown to see if the windshielf can hold the weight. That doesn't take into account lateral movement, however. Miatas have extremely reinforced A-pillars, but that doesn't change the fact that even they have to have real roll-bars installed to run in SCCA track events. Wanna know why? THIS IS WHY. Lateral pressure = bent A-frame = squished.

For example, if you roll over with this insead of this, this instead of this, this instead of this, or this instead of this, you are going to be in a world of hurt.
posted by Civil_Disobedient at 11:30 PM on August 21, 2005

Bear in mind that rolling your car is exceedingly uncommon, especially if it is a low-slung sports car. The usual situation where this occurs is with tall vehicles (especially SUVs) on uneven ground or soft shoulder.
posted by randomstriker at 12:27 AM on August 22, 2005

It may be less likely, mechanically or aerodynamically, but more likely statistically: the psychological factor of driving a sports car may lead one to take risks one wouldn't normally think of with a minivan. With great horsepower comes great responsibility.
posted by Civil_Disobedient at 10:29 AM on August 22, 2005