static shock from car: how to stop?

The type of rubber they are using these days is a lot less conductive, which is why this is more of a problem than it was a couple of decades ago. I don’t know the exact reason for it. Someone told me that it was because they were using silica instead of carbon in order to reduce the rolling friction but I haven’t looked into it further to confirm this.

Those grounding straps do work, and while you might find expensive scam versions on line, you can get grounding straps fairly cheap at ye ol local auto parts store. A short piece of chain will work as well. Just be careful that anything you hang can’t bounce up and get caught in anything that moves.

As for the tires, in the past few years, the dangers of static electricity at filling pumps has finally started to get some attention. Static discharges tend to cause on average about half a dozen pump fires every year, which isn’t exactly a huge number when you realize how many millions of cars there are out there filling up every week. But, since a pump fire can kinda ruin your whole day, folks have started paying more attention to it. Some tire manufacturers are now intentionally formulating their rubber so that it is more conductive, and some of those that aren’t are putting small carbon rubber strips (more conductive) on their tires to provide an electrical discharge path.

The actual problem is your underwear. Change the type of fabric of your underwear such that when you’re skidding (!) around twisties (!) in some mountain roads from side to side, your underwear doesnt rub with your jeans ( because your jeans will probably be firmly gripped by the cloth seats). Note that this type of static buildup doesn’t happen if you have leather seats.

from what i’ve heard that silica was placed in tires replacing carbon black to give better rolling resistance. providing conductive paths through tires requires a change in the manufacturing. i agree with engineer_comp_geek statement on this.

even if the car is grounded you have the static charge on you if you exit without grounding yourself. touching a conductive part of the car until your foot is on the ground and before your butt has left the seat will discharge the static.

no pants, no static. drive naked for safety.

That might be a bit uncomfortable in the winter. :stuck_out_tongue:

Seriously, though, your choice of clothing (or no clothing) does make a difference. Materials like wool, fur, and some synthetics like polyester are good at building up a static charge. Cotton clothes (like jeans) don’t build up a charge as easily.

Yes, I’ve found that holding on to a metallic part of the car while exiting appears to eliminate the static discharge shocks. As the electrical potential seems to be between you and the car, I can’t see what good grounding the car will do.

Wear different clothes, spray your upholstery with anti-static spray or hold on to a metallic bit of the car while decarring (de-car-ring?). Those are all good ways to cut the shocks. The car grounding strap doesn’t do anything for me, nor likely enough, for you.

There are two different situations you need to consider.

The first is that the charge differential is between yourself and the car. This is usually caused by you sliding across the seat, and what clothes you wear makes a huge difference in how much of a charge builds up, as does the material the seats are made out of. You are correct that grounding the car won’t make any difference at all in this situation. The rubber in the tires also makes no difference at all here.

The second situation is when the car builds up a charge differential between itself and the earth. This is caused by the rubber belt (or belts) on the engine as well as the movement of the car through air. Cars with conductive rubber tires will bleed off the charge very quickly. Cars with insulating tires will not. What you wear makes very little difference in this situation, but a ground strap will help in cases where the tires are of the insulating rubber type.

You can have both of these at the same time, and in either case the symptoms are the same. You get zapped.

had the same problem with their car - seriously painful shocks. My kids were scared of their car! They bought one of those grounding strips and we teased them that it looked like their car had a tail, but it absolutely worked. They just bought it at a local shop, not off the internet. They are Australian - maybe these strips are more common there. They didn’t seem to think this was an unusual device. Problem solved.
P.S. - we are in AZ, so it’s very dry all year round.

Used to have that problem in a Dodge Neon, but it wasn’t the car. It was my shoes, which had kind of a rubberized sole. When I started wearing leather-soled shoes, the problem disappeared. Various sneakers brought it back. Strange how I didn’t have that problem, though, with the same shoes in other cars.

the combination of shoe material and carpet material can build static charge in one case and not the other.

I wear denim (cotton) jeans most of the time, and they haven’t reduced the incidence of shocks.

I bought some Static Guard on Saturday; will apply it this week and see what happens.

Interesting! The original problem in the 1930s was glow-discharge ozone destruction of tire innertubes, and was solved by making tires conductive: increasing the carbon-black in the neoprene mix. (Carbon-black was already in there, it makes for a tough composite.)

Now that the innertubes don’t exist, maybe somebody is reducing the amount of carbon-black to where the rubber becomes an insulator. Note that ‘conductor’ and ‘insulator’ have an odd meaning here, since where electrostatic charging is concerned, 10^12 ohms is a resistive load, and tens of megohms is a good conductor.

Well, this is a more complicated topic than I expected. As I thought, there are hundreds of people on the internet with different explanations and cures. Some are much more scientific than others. Here in Straight Dope is the best summary I have found!

Certainly there are at least two different phenomena – one where the whole car and its occupants are electrostatically charged, and another which seems more recent, where the occupants get a charge within the vehicle. More recently still, apparently some modern low rolling resistance tyres no longer conduct enough electricity, and the original whole vehicle charge problem has returned.

I’ve previously had static shocks from two Toyota Corollas, several years apart. The zaps stopped completely in each case when I fitted a proprietary, slightly conductive trailing rubber anti-static strap under them. Many people have had the same results. But I just fitted one to our Honda Fit and got a painful shock for my troubles. Perhaps there was something else that happened to the Toyotas – maybe by coincidence we bought seat covers for them at around the same time as the straps were fitted? And we have another Corolla which has never shocked me…

Last night the air temperature was cold for Auckland (maybe 10° C, 50° F, so not cold by continental standards!), and the wind had been blowing down from the high country over several hundred km of wet ground, so its relative humidity wasn’t low. But even had it been saturated, at that temperature its absolute humidity would have been lower than usual.

I checked the new strap on the Honda this morning, and it measures something less than 300 k Ohms. So I’m reasonably confident that the car was close enough to ground potential when that nasty little blue spark took me completely by surprise.

Which implies that it was me, not the car, which was highly charged. And that it was the insulating qualities of my polyurethane soles which preserved that charge. I’m now working on the hypothesis that friction between my Merino wool jacket and the synthetic seat is responsible. (Everything else I was wearing was cotton.)

I’ve also checked the interior of the car with the meter. It’s certainly quite different from older cars. Although there is a lot of shiny “brushed stainless” it’s almost all totally non-conductive. There is only one possible object you can touch inside it which has any electrical connection to the car body, and that is the button on the hand brake. Every other control is plastic. The steering wheel and its various buttons, and all of the gearshift, all plastic. All steel parts of the body and door are covered by plastic trim. Seat controls, seat belt anchors, the whole radio, all plastic covered. Even the “cigarette lighter” power outlet is covered by a plastic door when not in use.

The ignition key fits into the lock between two plastic projections (which are what you use to turn it when you are using it in “keyless” mode using the credit-card-sized electronic “key”). Even the screw holding the internal door handle is insulated – it must go into a plastic insert. It is simply impossible to ground yourself to the car except by that little handbrake button!

Holding the key and using it to create a discharge isn’t a good option. The keys are expensive, with their sensitive little package of security electronics inside the thick plastic “handle” end. Anyway, I seem to get worse shocks when I’m not the driver. So I’ll try touching the handbrake before, and as I get out. Wish me luck!

Que the zombie jokes…

And the misspelling nitpickers.


or language and diction…