I tried wireless over Radio but the Receiver cant talk without a Timing parallel with two Transmitters.
What? I can call you on your cell phone, from my cell phone, and neither of our phones needs to know anything about the time, or any timing, on the other phone.
The next idea was a Serial communication (TX,RX) but is this possible to code with the sensor values exchange?
Of course. The serial port is used to send, and receive bytes. ALL data is made of bytes.
Another idea was a CanbusShield. Whats your experience with that one?
Adding another complete layer of complexity is not warranted.