The spacer grid assembly, an interconnected array of slotted grid straps embossed with dimples and springs, is one of the main structural components of a pressurized light-water reactor (PWR). It takes the role of supporting the nuclear fuel rods which experience a severe expansion and contraction caused by harsh operational conditions such as an earthquake. The external load by an earthquake can be mainly represented as a lateral load, and the resistance to it is evaluated in terms of dynamic crush strengths. It has been reported that a dimple location in a space grid has an effect on this strength. In this paper, based on this fact, the effect of a dimple location in a $3{ imes}3$ support grid on impact strength has been investigated as a preliminary parameter study for a full sized support grid. The optimal location of the dimple, about 3.5 mm from the tip of the strap, has been found and some design guidelines for a support grid such as reducing the spring length and the dimple gap have been provided.