Actually, the one and only reason that the narrow wheels aren't used is because the rule that was written immediately after the RC10t came out. The truck completely dominated the first few races it entered and the narrow wheels and tires were banned almost immediately. It was mainly the apperance of a monster truck that ROAR was trying to preserve. There was no good reason that Pro-Line and Losi couldn't make their own version. I believe trucks would handle much better with narrower front tires.
"I have no idea what you're talking about, so here's a bunny with a pancake on it's head."
In mind and body, we're all heading towards old age. It is slower to go by bike.