OpenRC F1 2017 improved rear axis with metal pin inside. There is a hole inside the model. The print must be paused at height of 5.2mm, then the pin can be inserted and the print can be resumed. The result is a very strong rear axis that is not braking when one of the rear tires hits hard.
The metal shaft is 3 mm in diameter and 150 mm long.
The author remixed this model.