diff --git a/urdf/diffbot_description.urdf.xacro b/urdf/diffbot_description.urdf.xacro
index 35021e7..020ab89 100644
--- a/urdf/diffbot_description.urdf.xacro
+++ b/urdf/diffbot_description.urdf.xacro
@@ -1,52 +1,52 @@
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@@ -75,13 +75,13 @@
ixx="${wheel_mass / 12.0 * (3*wheel_radius + wheel_len*wheel_len)}" ixy="0.0" ixz="0.0"
iyy="${wheel_mass / 12.0 * wheel_radius*wheel_radius}" iyz="0.0"
izz="${wheel_mass / 12.0 * wheel_radius*wheel_radius}"/>
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@@ -110,17 +110,17 @@
ixx="${wheel_mass / 12.0 * (3*wheel_radius + wheel_len*wheel_len)}" ixy="0.0" ixz="0.0"
iyy="${wheel_mass / 12.0 * wheel_radius*wheel_radius}" iyz="0.0"
izz="${wheel_mass / 12.0 * wheel_radius*wheel_radius}"/>
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@@ -140,83 +140,86 @@
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+ ixx="${2.0/5.0 * caster_wheel_mass * caster_wheel_radius * caster_wheel_radius}"
+ ixy="0.0" ixz="0.0"
+ iyy="${2.0/5.0 * caster_wheel_mass * caster_wheel_radius * caster_wheel_radius}"
+ iyz="0.0"
+ izz="${2.0/5.0 * caster_wheel_mass * caster_wheel_radius * caster_wheel_radius}"/>
+
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diff --git a/urdf/diffbot_description.urdf.xacro.bak b/urdf/diffbot_description.urdf.xacro.bak
new file mode 100644
index 0000000..35021e7
--- /dev/null
+++ b/urdf/diffbot_description.urdf.xacro.bak
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