diff --git a/interface/src/avatar/AvatarMotionState.cpp b/interface/src/avatar/AvatarMotionState.cpp
index 50c715b14a..07e6b3f6b0 100644
--- a/interface/src/avatar/AvatarMotionState.cpp
+++ b/interface/src/avatar/AvatarMotionState.cpp
@@ -19,6 +19,7 @@
 AvatarMotionState::AvatarMotionState(AvatarSharedPointer avatar, const btCollisionShape* shape) : ObjectMotionState(shape), _avatar(avatar) {
     assert(_avatar);
     _type = MOTIONSTATE_TYPE_AVATAR;
+    cacheShapeDiameter();
 }
 
 void AvatarMotionState::handleEasyChanges(uint32_t& flags) {
@@ -57,9 +58,6 @@ PhysicsMotionType AvatarMotionState::computePhysicsMotionType() const {
 const btCollisionShape* AvatarMotionState::computeNewShape() {
     ShapeInfo shapeInfo;
     std::static_pointer_cast<Avatar>(_avatar)->computeShapeInfo(shapeInfo);
-    glm::vec3 halfExtents = shapeInfo.getHalfExtents();
-    halfExtents.y = 0.0f;
-    _diameter = 2.0f * glm::length(halfExtents);
     return getShapeManager()->getShape(shapeInfo);
 }
 
@@ -98,6 +96,10 @@ void AvatarMotionState::setWorldTransform(const btTransform& worldTrans) {
         btVector3 velocity = glmToBullet(getObjectLinearVelocity()) + (1.0f / SPRING_TIMESCALE) * offsetToTarget;
         _body->setLinearVelocity(velocity);
         _body->setAngularVelocity(glmToBullet(getObjectAngularVelocity()));
+        // slam its rotation
+        btTransform newTransform = worldTrans;
+        newTransform.setRotation(glmToBullet(getObjectRotation()));
+        _body->setWorldTransform(newTransform);
     }
 }
 
@@ -141,7 +143,10 @@ glm::vec3 AvatarMotionState::getObjectLinearVelocity() const {
 
 // virtual
 glm::vec3 AvatarMotionState::getObjectAngularVelocity() const {
-    return _avatar->getWorldAngularVelocity();
+    // HACK: avatars use a capusle collision shape and their angularVelocity in the local simulation is unimportant.
+    // Therefore, as optimization toward support for larger crowds we ignore it and return zero.
+    //return _avatar->getWorldAngularVelocity();
+    return glm::vec3(0.0f);
 }
 
 // virtual
@@ -174,3 +179,28 @@ float AvatarMotionState::getMass() const {
     return std::static_pointer_cast<Avatar>(_avatar)->computeMass();
 }
 
+void AvatarMotionState::cacheShapeDiameter() {
+    if (_shape) {
+        // shape is capsuleY
+        btVector3 aabbMin, aabbMax;
+        btTransform transform;
+        transform.setIdentity();
+        _shape->getAabb(transform, aabbMin, aabbMax);
+        _diameter = (aabbMax - aabbMin).getX();
+    } else {
+        _diameter = 0.0f;
+    }
+}
+
+void AvatarMotionState::setRigidBody(btRigidBody* body) {
+    ObjectMotionState::setRigidBody(body);
+    if (_body) {
+        // remove angular dynamics from this body
+        _body->setAngularFactor(0.0f);
+    }
+}
+
+void AvatarMotionState::setShape(const btCollisionShape* shape) {
+    ObjectMotionState::setShape(shape);
+    cacheShapeDiameter();
+}
diff --git a/interface/src/avatar/AvatarMotionState.h b/interface/src/avatar/AvatarMotionState.h
index 9228641b25..a458704b1a 100644
--- a/interface/src/avatar/AvatarMotionState.h
+++ b/interface/src/avatar/AvatarMotionState.h
@@ -74,6 +74,10 @@ public:
     friend class Avatar;
 
 protected:
+    void setRigidBody(btRigidBody* body) override;
+    void setShape(const btCollisionShape* shape) override;
+    void cacheShapeDiameter();
+
     // the dtor had been made protected to force the compiler to verify that it is only
     // ever called by the Avatar class dtor.
     ~AvatarMotionState();
diff --git a/libraries/physics/src/ObjectMotionState.cpp b/libraries/physics/src/ObjectMotionState.cpp
index 310cf7cec1..c814140930 100644
--- a/libraries/physics/src/ObjectMotionState.cpp
+++ b/libraries/physics/src/ObjectMotionState.cpp
@@ -64,9 +64,9 @@ ShapeManager* ObjectMotionState::getShapeManager() {
 }
 
 ObjectMotionState::ObjectMotionState(const btCollisionShape* shape) :
-    _shape(shape),
     _lastKinematicStep(worldSimulationStep)
 {
+    setShape(shape);
 }
 
 ObjectMotionState::~ObjectMotionState() {
diff --git a/libraries/physics/src/ObjectMotionState.h b/libraries/physics/src/ObjectMotionState.h
index 7439c1c38d..74173c3f47 100644
--- a/libraries/physics/src/ObjectMotionState.h
+++ b/libraries/physics/src/ObjectMotionState.h
@@ -175,13 +175,13 @@ protected:
     virtual void setMotionType(PhysicsMotionType motionType);
     void updateCCDConfiguration();
 
-    void setRigidBody(btRigidBody* body);
+    virtual void setRigidBody(btRigidBody* body);
     virtual void setShape(const btCollisionShape* shape);
 
     MotionStateType _type { MOTIONSTATE_TYPE_INVALID }; // type of MotionState
     PhysicsMotionType _motionType { MOTION_TYPE_STATIC }; // type of motion: KINEMATIC, DYNAMIC, or STATIC
 
-    const btCollisionShape* _shape;
+    const btCollisionShape* _shape { nullptr };
     btRigidBody* _body { nullptr };
     float _density { 1.0f };
 
diff --git a/libraries/shared/src/PhysicsCollisionGroups.h b/libraries/shared/src/PhysicsCollisionGroups.h
index 9d99ec3532..ef18cb0b0e 100644
--- a/libraries/shared/src/PhysicsCollisionGroups.h
+++ b/libraries/shared/src/PhysicsCollisionGroups.h
@@ -59,7 +59,11 @@ const int32_t BULLET_COLLISION_MASK_KINEMATIC = BULLET_COLLISION_MASK_STATIC;
 // MY_AVATAR does not collide with itself
 const int32_t BULLET_COLLISION_MASK_MY_AVATAR = ~(BULLET_COLLISION_GROUP_COLLISIONLESS | BULLET_COLLISION_GROUP_MY_AVATAR);
 
-const int32_t BULLET_COLLISION_MASK_OTHER_AVATAR = BULLET_COLLISION_MASK_DEFAULT;
+// OTHER_AVATARs are dynamic, but are slammed to whatever the avatar-mixer says, which means
+// their motion can't actually be affected by the local physics simulation -- we rely on the remote simulation
+// to move its avatar around correctly and to communicate its motion through the avatar-mixer.
+// Therefore, they only need to collide against things that can be affected by their motion: dynamic and MyAvatar
+const int32_t BULLET_COLLISION_MASK_OTHER_AVATAR = BULLET_COLLISION_GROUP_DYNAMIC | BULLET_COLLISION_GROUP_MY_AVATAR;
 
 // COLLISIONLESS gets an empty mask.
 const int32_t BULLET_COLLISION_MASK_COLLISIONLESS = 0;