Complex sentence: In 1963, Howard Hawkins and Art Engstrom were the owners of three bicycle shops in the Twin Cities area when they started noticing that there were no tools available to repair the increasingly complex bicycles of the 1960s, and began creating their own tools.
Split into simpler sentences: In 1963, Howard Hawkins and Art Engstrom were the owners of three bicycle shops in the Twin Cities area. They noticed that there were no tools available to repair the increasingly complex bicycles of the 1960s, so they began creating their own tools.