Just let him drive your trucks. I let my 8 year old drive all my trucks. So far, the only things he bent was the titanium skids on the supermaxx and predator. No broken parts on the nitro and brushless revo so far. I let him drive the ST-RR yesterday and he said, "Dad, can I have it?" I replied "just concentrate driving"
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Kids are fast learners. You'll be surprised how quick they learn things especially if they're really interested. I coached him when to brake, turn, throttle up as he goes around the track. It came to a point where he told me yesterday that I just need to be quiet so he can concentrate.