Why am I getting a shock every time I touch my truck's door?

Dear Car Talk

Dear Car Talk | May 01, 1996

Dear Tom & Ray:
I have a '96 Dodge Dakota, and whenever I leave the truck, I get a shock
when I touch the door. This is really starting to tick me off. Other than
wearing a rubber suit and gloves, what can I do? -- Duke

RAY: It's back! Another static-electricity epidemic. There was a static
explosion in the mid- 1970's, mostly attributable to the proliferation of
polyester leisure suits. But the current static-electricity problem seems
to have its roots in tires.

TOM: Yes, tires! The tires play a role in grounding the car and diffusing
the natural buildup of static electricity. But many of today's tires are so
called "low rolling resistance" tires, which reduce rolling friction in
order to improve gas mileage.

RAY: Instead of using a compound called "carbon black" to hold the rubber
together, these "low rolling resistance" tires use "silica" as their
reinforcing agent. That improves gas mileage, but decreases a tire's
ability to diffuse static.

TOM: So under certain conditions -- particularly when the air is dry --
cars with these tires can deliver significant shocks to unsuspecting,
exiting passengers. And if you're driving in a car with low rolling
resistance tires on a dry day while wearing a polyester leisure suit, well,
you'll probably look like a sign outside a Las Vegas hotel when you grab
the door handle.

RAY: Here's what I'd do, Duke. Since the truck is still brand-new, I'd take
if back to the dealer and ask if they'll swap the tires for you. Ask them
for some nice, gummy, high rolling resistance treads.

TOM: If they won't do that, or if every ounce of gas mileage is important
to you, invest in a pair of those static diffusing rubber strips that
attach to the truck's frame and hang down and drag along the ground.

RAY: Yeah. I got a pair of those for my wife. Her minivan shocks her every
time she gets out and touches the door handle. And as soon as she agrees to
stop serving broccoli five times a week, I'm going to install them for her.

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