Not so. It's well known phenomenon called  "wheel static" or tire 
static. I  believe the actual insulating junction might be the front 
wheel bearings that ride on a thin film of grease and do not have 
metal-to-metal contact whilst the wheel is spinning.  You can read about 
it in the older editions (1950's and 1960's) of the ARRL Mobile Handbook 
for example.

Touching the brakes make a connection between the car body and the tire 
in this case through the brake pads which have enough conductivity to 
discharge the build up.

When raining the problem would not occur as there would be enough of a 
leakage path to discharge the car body to ground. Even going  through a 
puddle would provide leakage until the water dried off.

I observed this consistently for two years until the new tires were 
installed, and I had chats with the Volvo dealer about it and they all 
agreed that it did happen and thought there was an old service bulletin 
about it for earlier models but couldn't find it.


Jack


Olin Lathrop wrote:
> Jack Smith wrote:
>   
>> I bought the Cling-Free spray three or four years ago to spray on the
>> tires of my automobile. The particular tires on it were highly
>> non-conductive and would build up large amounts of "wheel static" that
>> totally wiped out AM radio reception when traveling on the interstate
>> system at reasonable speed. Touching the brake pedal would discharge the
>> voltage potential out for a few minutes until it built up again.
>>     
>
> Huh?  Why would touching the brake pedal have anything to do with
> discharging static buildup between the car and the ground?  The insulation
> of the tires between the road and the car frame should still be there
> whether the brake is applied or not, unless of course you have Fred
> Flinstone brakes.  I think something totally different was going on than you
> think.
>
>
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