Bump when crossing box colliders

I am creating a 3D game where I need to have a grid playing surface. Each cell of this grid has its own box collider so that I can manipulate certain parts of the grid. I then have a player car that must travel across the grid smoothly.

However, there seems to be some sort of inconsistency in the box colliders. This causes the car to pop up each time it crosses into a new cell like this Imgur: The magic of the Internet . Also this is with very large cells where eventually I will be using much smaller cells. While testing this, the car can hardly move.

I have tried lowering the “Default contact offset” which makings it slightly better, but then causes the car to get all jittery.

Are the colliders separated by that light grey area or are they right next to each other?? I don’t know how you placed the box objects with the colliders, but if they are not exactly level on the seems, that could cause the weird effect. Use the snap feature to get exact results. Holding CTRL (PC) or CMD (Mac). Also use V to snap Vertices together. You can change the snap settings (distance) in Edit/Snap Settings…