>> At the speedway where I grew up (Oswego Speedway
>> http://www.oswegospeedway.com/), the raced what they would call
>> "super modified" cars. One of the drivers showed me his car once
>> and it looked to me like they pretty much would build the cars
>> from the ground up. Anyway, the tires on these cars had no tread
>> on them whatsoever. It made me wonder why that didn't cause a
>> problem getting a good grip on the pavement. I still don't know,
>> but the racing tires looked completely smooth.
>> Like this:
>>
>> ------------------------------------------------------------------------
>>
>
> No tread actually grips a smooth track better.  The problem is that
> once you overcome the friction and lose traction, you lose complete
> control of the car.  The tread is like a claw that grabs the
> ground, giving back control.
>
> You'll see them switch between the no-tread and treaded tires in
> situation when they think they could lose traction, ie when it looks
> like it'll rain they put on treaded tires.  The all-weather tires
> most people use on their cars have tread for this same reason, and
> snow tires have an unusually pronounced tread on them.

Actually the tread is used on road cars (and racing cars in the wet) to 
ensure the car doesn't aquaplane (ie float on the water with no contact to 
the road).  The water goes into the tread gaps and allows the rest of the 
rubber to actually hit the road surface.  If you used slicks they would just 
skim across the surface with no contact at all to the road.

If you've driven too fast across a deep puddle in your road car you will be 
familiar with the loss of grip.

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