For decades automakers have promoted the towing capacity of their vehicles, particularly pickup trucks, as a selling point. What many consumers did not know was that the industry had no standard to ensure apples-to-apples comparisons and to prevent companies from making unrealistic claims.
"I think in many ways consumers just went with what was printed in the brochure and took no real thought as to how it was developed," said David Champion, director of auto testing for Consumer Reports.
That will soon change. SAE International, the group formerly known as the Society of Automotive Engineers, has established a voluntary standard that specifies how automakers should measure towing capacity.
"My personal opinion is that some of the numbers were getting a little carried away," said Robert Krouse, a General Motors engineer specializing in towing who is also chairman of the SAE committee that came up with the standard.
If automakers choose to use the SAE standard, consumers should come out ahead. "The good part is that the numbers should be more directly comparable, so a Toyota 10,000 pounds and a GM 10,000 pounds and a Ford 10,000 pounds should be pretty similar," Krouse said.
The new standard, called J2807, specifies not just how quickly a vehicle must be able to accelerate, but also how it stops and how it handles. With increases in horsepower and torque it is possible for a vehicle to tow a trailer that outweighs it, creating potential challenges to drivers, Krouse said.
"Being able to handle the trailer is an even more critical part of the equation," he said. Poor handling "sneaks up on you," he said. So the vehicle's suspension must be able to resist a trailer's fishtailing.
One implication of the new standard is that towing numbers are likely to drop by 200 to 500 pounds.
Previously, the tested vehicle could be a stripped-down model without options, and only a driver needed to be on board. Now there must be a driver and a 150-pound passenger as well as typical options like air-conditioning. That could decrease towing capability by 200 to 500 pounds, Krouse said.
The standard covers cars, minivans, SUVs and all but the largest heavy-duty pickups and likely will take effect in 2012.