diff --git a/frc971/control_loops/drivetrain/drivetrain_config.h b/frc971/control_loops/drivetrain/drivetrain_config.h
index c4652be..88547d5 100644
--- a/frc971/control_loops/drivetrain/drivetrain_config.h
+++ b/frc971/control_loops/drivetrain/drivetrain_config.h
@@ -72,6 +72,10 @@
   Scalar high_gear_ratio;
   Scalar low_gear_ratio;
 
+  // Moment of inertia and mass.
+  Scalar J;
+  Scalar mass;
+
   // Hall effect constants. Unused if not applicable to shifter type.
   constants::ShifterHallEffect left_drive;
   constants::ShifterHallEffect right_drive;
diff --git a/frc971/control_loops/drivetrain/drivetrain_lib_test.cc b/frc971/control_loops/drivetrain/drivetrain_lib_test.cc
index 49022f6..e4d320e 100644
--- a/frc971/control_loops/drivetrain/drivetrain_lib_test.cc
+++ b/frc971/control_loops/drivetrain/drivetrain_lib_test.cc
@@ -54,6 +54,8 @@
 
       ::y2016::control_loops::drivetrain::kHighGearRatio,
       ::y2016::control_loops::drivetrain::kLowGearRatio,
+      ::y2016::control_loops::drivetrain::kJ,
+      ::y2016::control_loops::drivetrain::kMass,
       kThreeStateDriveShifter,
       kThreeStateDriveShifter,
       false,
diff --git a/frc971/control_loops/drivetrain/trajectory_test.cc b/frc971/control_loops/drivetrain/trajectory_test.cc
index 58f0a22..89b5ffb 100644
--- a/frc971/control_loops/drivetrain/trajectory_test.cc
+++ b/frc971/control_loops/drivetrain/trajectory_test.cc
@@ -60,6 +60,8 @@
 
       ::y2016::control_loops::drivetrain::kHighGearRatio,
       ::y2016::control_loops::drivetrain::kLowGearRatio,
+      ::y2016::control_loops::drivetrain::kJ,
+      ::y2016::control_loops::drivetrain::kMass,
       kThreeStateDriveShifter,
       kThreeStateDriveShifter,
       false,