Why does my robot skid ?

edit

Hi all. I have a simple robot (like a car) but when it rolls it skids and I don't want it

I tried : - Decrease / increase mass
- Set mu1 and mu2 of every links to Inf - Set mu1 and mu2 of my world ground plane to inf

Joint between motor and wheel :

  <xacro:property name="BOTTOM_ENGINE_PROPULSION_MAX_EFFORT" value="5000" /> 
  <xacro:property name="BOTTOM_ENGINE_PROPULSION_MAX_VELOCITY" value="100.0" />


<joint name="bottom_${side}_engine_to_${side}_wheel" type="continuous">
  <origin xyz="0.0 0.0 ${-BOTTOM_ENGINE_HEIGHT/2.0}" />
  <parent link="bottom_${side}_engine" />
  <child link="${side}_wheel" />
  <axis xyz="0 -1 0" />
  <limit effort="${BOTTOM_ENGINE_PROPULSION_MAX_EFFORT}" velocity="${BOTTOM_ENGINE_PROPULSION_MAX_VELOCITY}" />
</joint>

<gazebo reference="bottom_${side}_engine_to_${side}_wheel">
  <disableFixedJointLumping>true</disableFixedJointLumping>
</gazebo>

Here is a video to illustrate my problem :

https://youtu.be/O--KlG6fj5s

In the video I publish :

rostopic pub /robot/left_wheel_traction_controller/command std_msgs/Float64 "data : 5.0" (5.0 rad/s on wheel) rostopic pub /robot/right_wheel_traction_controller/command std_msgs/Float64 "data : 5.0" (5.0 rad/s on wheel)

Does someone have an idea why the robot is sliping ?