Some margin while using btConvexTriangleMeshShape

[muhaos]

When I use for Collision Shape a some btConvexTriangleMeshShape it seems to be some margin between collided objects. But this margin is disappear if I use some primitive collision shape (ie box or sphere).
A have attached screens with btConvexTriangleMeshShape (left) and btBoxShape (right). btBoxShape looks fine, but btConvexTriangleMeshShape not.

Sorry for ma English %)