Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Second opinion on CarShock

Today’s broadcast (13Dec08—could be a rebroadcast, I don’t listen all that closely) had another of your periodic “My car shocks me when I get out (not just when I open the garage door)” topics. You always recommend installing grounding straps, but these eventually wear, so it isn’t really a long-term solution.

There is an extremely simple solution which costs nothing and lasts indefinitely: just grab the door frame as you step out before your foot touches the ground. The discharge then goes between your foot and the ground which (unless you are barefoot as well as naked) you can’t feel.

[I find it hard to believe no one has pointed this out yet. Although I suppose I could well be just making it obvious that I haven’t browsed the list before posting. If so, apologies.]

That’s what I always do too!

A driver sitting in a car which builds up a static charge due to the rolling tires should have the same static potential as the car. Any spark should then occur between the driver and ground not between driver and car. The simplest explanation is the old one: the friction between clothes and seat fabric causes a potential difference between the driver and car. Same thing happens between me and my chair at work when the air is dry. I don’t think it is due to those little wheels rolling on the carpet.

This is the entire reason I signed in today. I’ve been meaning to do this for weeks.

It doesn’t matter if the static is built up in the car, the person’s body, or the ground. If you grab the metal of the car when you step on the ground the static build up will be neutralized. If you slide out and then turn and touch the car the static potential, wherever it may be, is going to discharge through the air between your hand and the car and it’s going to hurt.

I agree about the clothing because I’ve noticed that when I wear all cotton clothing, I don’t get any shocks. But your premise on the spark being between the driver and ground is not correct, well it would be if the driver holds onto to a metal part of the body as suggested by the OP.

If the driver builds up a static charge with the car, regardless of whether its due to tires or clothing, when the driver exits the vehicle, the charge on their body discharges through their feet. Due to the wide area of contact between the body and the shoes, the discharge is not felt. However, when the driver then touches the car body, the car is then discharged through the drivers body. The discharge occurs on a very small area of skin, like a finger tip so the shock is felt at that point.

Holding onto a metal part of the body while exiting the vehicle keeps the discharge over wide areas where it is not felt. There are shoes available with ESD soles used in the electronics industry. You will never feel a shock wearing these shoes. Unfortunately, they all are made with steel or composite safety toes so they tend to be heavy and somewhat uncomfortable.

If there was a public outcry to get shoe manufacturers to use these types of soles on all shoes, like the outcry on broken timing chains has caused many auto manufacturers to switch to timing chains, maybe we could get them on everyday shoes.

I used to get a zap when I had cloth seats. Now I have a newer model of the same truck with leather seats…guess what…no shock.

There was a “public outcry” over timing chains,or even timing belts? I missed that one.