Some prominent truckload fleets will report weak third-quarter earnings in part because of lost productivity related to the hours-of-service rule change that took effect July 1, company officials and analysts said.    

Continuing weakness in North American heavy-duty truck sales took a toll on second-quarter earnings for a group of major truck suppliers, most of which remained profitable but at lower levels than the same quarter in 2012.

Goodyear Tire & Rubber Co.’s second-quarter earnings more than doubled as its operating income jumped 27%, improving in all four of its global regions.

Heavy-duty truck makers reported lower second-quarter profits and revenue, compared with a year ago, as the U.S. economy gradually improves.

Rush Enterprises said its second-quarter profit declined from a year ago on lower sales and a retirement charge, and announced its intention to buy truck dealerships in three states.

Canada’s two major freight railroads reported higher second-quarter earnings from a year ago on stronger rates and volume.

Landstar System said it expects its second-quarter profit to be between 63 and 68 cents per share, 5 cents below its earlier forecast.