How is the friction setting for wheels called?

Essentially I want a script to change a wheel's friction on command. The problem is that I don't know how that setting is called because it didn't exist at the time they made the documentation. I already ran into a similar problem earlier when I wanted to change the height offset, but after some guessing it turned out to be simply "Height".
For the friction setting the keyword doesn't seem to be "Friction" though. Can anyone tell me what it is, or even better where you can read up stuff like...

How is the friction setting for wheels called?