Need Help with Wheel Collider Friction

I have two tanks, using eight wheel colliders to move and steer on each tank.

When I drive one tank into the other, they push each other over like they're made of paper, no matter what the masses are. I'm pretty sure this is an issue with the wheel colliders having way too much traction and so just tipping over instead of slipping, but I don't really understand the friction curves well enough to create curves that would actually work, and need suggestions from anyone who's used them before.

As a side note, I also had problems with them being able to climb near-vertical surfaces, and had to create a script just to stop that. If I could do this through a better set of traction curves instead of a strict limit on slopes, that would be great.

So any suggestions on wheel friction curves?