SAO PAOLO, May 18 (Reuters) - Sweden's SKF , the world's biggest bearings maker, sees firm growth in the markets for heavy trucks in Europe and North America, a top executive said on Wednesday. "The indications we have from our customers show that the European market will grow by about 6 percent this year," Tryggve Sthen, head of SKF's Automotive division, told journalists on the sidelines of a capital market day in Brazil.