Hello xtaiji,
Nice vid you posted up to the JConcepts thread. I like a small track. We have so few anymore for 1/8 nitro here in the U.S.
Tires? Give JConcepts a try since you posted to their thread. Also, check with Sweeps. I see it in your signature line. Some of the Texas racers are trying Sweeps. We're mostly hard clay here.
Korea is one of my favorite places. U.S. Army posted my wife and I there 1998-2000. Yongsan, Seoul. That's where I got hooked on r/c. Fond memories.
Cheers, Keep the shiny side up. 'AC'