I constantly get zapped when I get out of my cars when the humidity is low.

Dear Car Talk

Dear Car Talk | Jun 01, 1997

Dear Tom and Ray:

I constantly get zapped when I get out of my cars when the humidity is low.
Is there any way of stopping this short of dragging a chain from my
undercarriage like the old fuel trucks used to do (yeah, I'm that old!)? In
the dead of winter, I have actually sparked a 2-inch lightning bolt, enough
to light up the neighborhood. -- Charlie

TOM: C'mon, Charlie, what kind of man are you? What's a few hundred volts
of electricity between and man and his car every now and then?

RAY: Actually, there are several things that exacerbate static electricity
problems in cars, Charlie. One is the relative humidity. When the air is
very dry -- like in the winter -- static electricity is worse.

TOM: The second factor is tires. Tires play a crucial role in discharging
the static electricity that builds up while you drive. And lots of newer
"low rolling resistance" tires are poorer at discharging static than older
tires that used more of a substance called "carbon black."

RAY: The final factor is sartorial, Charlie: those polyester leisure suits
you wear. And we know you're of the generation that wears them because
you're old enough to remember fuel trucks dragging chains!

TOM: OK, well, let's assume for the moment that you're a man of the '90s
and you go light on the polyester. And let's assume you have no personal
influence over relative humidity.

RAY: So the only thing you can really influence is how well your car
discharges the static electricity. So you can either go to "higher rolling
resistance" tires, which is impractical because tires are expensive and
because increasing your rolling resistance will reduce your gas mileage. Or
you can find another way to discharge the "charge."

TOM: You have three options here. One is to discharge it yourself while
exiting the car. If you hold your key and touch the end of it to some metal
part of the car, the built-up charge should jump from the end of the key to
the car, "hurting" the end of the key and not your finger. The downside is
that you do have to remember to do this, and you look kind of stupid
cringing wearily while poking your key all over your car as you get out.

RAY: The second option is a pair of rubber grounding strips that you hang
off your undercarriage. You can buy these at auto parts stores. They have a
metal wire embedded in the rubber, and they hang down and discharge the
static as it builds up. And they work pretty well. The only downside is
they tend to be real cheap junk, and they wear out every six months or so
and need to be replaced.

TOM: Your final option is to hang a chain under the car, like the old fuel
trucks did. That's certainly the cheapest solution. And while most people
would find that intolerably noisy, we figure at your age, Charlie, you
might not even hear it!

* * *

If you want to ruin your car, we have 10 ways for you to do it. If you
don't want to ruin your car, we have "Ten Ways You May Be Ruining Your Car
Without Even Knowing It!" You can order this booklet by sending $3 and a
stamped (55 cents), self-addressed No.10 envelope to Ruin No.1, PO Box
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