# How to avoid the joint deformed

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Hi guys, I build an Ackermann car. Now I meet a problem, the joint is deformed by gravity, which is shown in the gazebo. But in Rviz or lift the car on a plant with front wheels not attach to the ground, the deform will not happen. If I cancel the gravity on the chassis, the deformation will also disappear, but gravity is necessary for driving test and simulation. These are my .xacro code for one side front wheel:

<link name="link_front_right_wheel">
<inertial>
<mass value="0.04"/>
<origin rpy="0 -1.5707 -1.5707" xyz="0 0 0"/>
<inertia ixx="1.36433e-5" ixy="0" ixz="0" iyy="1.36433e-5" iyz="0" izz="0.00002312"/> <!--ixx=iyy=mass*(L^2+3*R^2)/12;izz=mass*R*R/2-->>
</inertial>
<origin rpy="0 -1.5707 -1.5707" xyz="0 0 0"/>
<geometry>
</geometry>
</collision>
<visual>
<origin rpy="0 -1.5707 -1.5707" xyz="0 0 0"/>
<geometry>
</geometry>
</visual>

<joint name="joint_front_right_wheel" type="continuous">
<origin rpy="0 0 0" xyz="0 -0.015 0"/>
<axis rpy="0 0 0" xyz="0 1 0"/>
<limit effort="0.1" velocity="38"/>
<joint_properties damping="0.01" friction="0.3"/>
</joint>

<inertial>
<mass value="1e-5"/>
<origin rpy="0 0 0" xyz="0 0 0"/>
<inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6"/>
</inertial>
<origin rpy="0 0 0" xyz="0 0 0"/>
<geometry>
</geometry>
</collision>
<visual>
<origin rpy="0 0 0" xyz="0 0 0"/>
<geometry>
</geometry>
</visual>