In this paper, we are focusing in the tolerancing of great dimension hydraulic systems which are overconstrained. For such systems, components fixings are linked to a rigid structure which more generally presents geometrical deviations. Moreover, pipe manufacturing process also creates some variations. The contribution of our approach is to determine by simulation the mechanical stresses between components, introduced by the actual geometry and the brackets position. In the paper, we first present the technological components characteristics, their geometrical manufacturing deviations and the joint constraints between components. Then we detail the proposed model which relies on a classical strength of material approach. In particular, this model uses tube flexibility in order to make-up for the manufacturing and positioning geometrical deviations. At final, this approach should lead to define the allowance amplitude of the different geometrical deviations.