Left rear tire loosening up
 

Is solution up of the left rear tire on a traxxas slash two-wheel drive caused by the reverse torque when braking? Is there any way to prevent it?

If you don't have them already then use "flanged, knurled 4mm locknuts." In most instances it doesn't come loose anyhow unless it was a bit loose before you started your run.

Yes, those pesky little buggers (left side) always seem to cause trouble. Thread lock for extra insurance.

Why don't you want to admit the goold old screw in your tire? Get it to the tire repairs and ask to check. I think they'll quickly find out where the problem is.

You lost? You're on an rc car forum. I use something like these without anything coming loose. Mine are sae threads but they work the same.
Locknuts | McMaster-Carr