Vehicle slows down, while touching two platforms

So, i have a game, something like skyroads, where you drive a vehicle forward, jump on other platforms, etc.

I am using rigid.velocity to move the vehicle, and my problem is, when the vehicle is on the “connection” between two different platforms (like here), it’s speed and acc is about 40% worse.

How do i fix that?

Check the physics material. It probably has to do with the friction combine.

http://docs.unity3d.com/Documentation/Components/class-PhysicMaterial.html