This seems like it's enough to screw up the tire balance.
Does this stuff eventually come off ?

 

IME it has always come offf my RE-71R pretty fast. Like I never notice it again after I drove the car on the street.

 

Think of it as a gift. its pretty evenly distributed over a tire and you get to use the track rubber instead of your own for a week or two. (a couple of 100 miles and its gone.) this isnt much, but on the race car , sometimes i pick up a LOT of rubber.. a full coating, that lasts a long time on the street. the marbles in the wheel usually upset the balance more.

 

On the street, it can take a long time to scrub off. On the track, it's pretty much gone after just a few hard laps

 

Scrub the tires on a road that you won't get pulled over (right/left turns in rapid succession).