My youngest son and I started racing R/C cars when he has about ten years old, so about eighteen years ago. We ran traditional 1/12 scale foam tired pan cars in the stock motor class with a battery limit and 1/10th scale 4WD touring car, also stock motor class with a battery limit. These ran on handout spec rubber tires. These were our indoor, winter season cars.
Outdoors in the summer was all about the gas cars. We ran the 1/10th scale 4WD touring cars, with spec .12 motors and rubber tires. We had a ball doing this for about six years, until he got old enough to drive. We probably would have stuck with it, but first the outdoor series than the indoor facility just kind of dwindled and went away.
Here are a couple of photos of our gas touring cars. These were Associated RC10's, with shaft drive and two speed centrifugal transmissions. We ran a solid spool in place of the diff in the rear, and a "one way" diff in the front. His was the yellow car, mine the blue.
I wound up getting a little silly and adapting a four cycle motor to mine, and O.S. FS26. This thing revved to less than half the rpm of the two stroke .12's, so gearing it was a real challenge. It sounded really, really cool, though, with that four stroke.
Mains for the electric cars in this pre-brushless and lipo era were five minutes for touring cars and eight for the 1/12 pan cars. One really had to manage his batteries to make it to the end. Mains for the gas cars were up to 45 minutes, with pit stops for fuel. You can see in the photos how we refueled, through the windshield cooling hole and a hatch in the gas tank.
This was fun stuff, and a really good way to spend time with my son. He was able to learn to work on his cars, how set-up changes affected them, and, most importantly, sportsmanship. Those were good times.