Inside part of the tire creating rubber

Hey guys. What can cause this in the tires?

i’m running 0 camber, and I never measured the toe.
Also my rear tires are doing this a little bit.

is this normal?

Normal. Karts depend on chassis flex and lots of front steering geometry to work, and it naturally wears the inside edge more. More pronounced on softer tires. Those tires looks used up though.

They have more than 100 laps lol