Not everyone would put their job on the line for an independent rear suspension.
Tim Herrick is not everyone. The career engineer at General Motors spent the last four or five years working on the massive truck program known as T1 that underpins GM’s light-duty pickups, heavy-duty trucks, and full-size SUVs.
The plan was always to distinguish the big SUVs, Tahoe and Suburban, from the pickups. On Herrick’s wish list from the start was an independent rear suspension for the SUVs. Ford has had an independent rear suspension on the Expedition and Expedition Max for years. Herrick knew the benefits, and he wanted it for GM’s large SUVs even though the pickups continued to use a leaf-sprung solid rear axle.
“We took a number of runs at it,” said the man whose work on trucks dates back to the Chevy Avalanche that went into production in 2001. It was an expensive request. Not only are the components heavier and more expensive, but it also would require tearing up the assembly process and building a new body shop at the plant in Arlington, Texas.
It was a big ask, even on a vehicle program unprecedented in size, scope, and the billions in capital investment. But the large trucks and SUVs are GM’s best-selling and most profitable vehicles.
“This was timely,” said Herrick this week ahead of the global reveal of the 2021 Chevy Tahoe and Suburban that go on sale next spring with—you guessed it—their first-ever independent rear suspension.
Getting approval, after many requests and rejections, was a big deal. “I can tell you the date and the time,” said Herrick. “It was a few years back on June 16, at 10:30. I went to a certain meeting and got approval to do it. It wasn’t the first time we asked. We had to really push to the point where I might have staked my career on it.”
That is hyperbole, right? Swapping out a live rear axle improves driving dynamics and provides a lower flat floor resulting in more passenger and cargo space and seats that slide and fold flat. But are the benefits worth staking a lengthy career on? Or his position as executive chief engineer for full-size trucks?
So how did he prevail? “I sat with a certain leader of our company and I cut a deal,” Herrick told MotorTrend. “It was multimillions of dollars and I told this person that if they thought that this was a bad decision and we launched this, well, to say I staked my career might be a bit strong but I said, ‘I’ll make you a deal: If we get to the reveal, or if we launch this and you think this was a dumb idea, I’ll hand you my badge and let you walk me out. ‘”
Herrick still has his badge. He was on stage presenting the new SUVs to the media and dealers in Detroit this week. He was recently promoted to vice president of Global Product Programs. He said those who were part of the decision are extremely happy.
“We really pushed,” Herrick said, convinced the packaging benefits, safety benefits in the way the rear rails straighten out to control the load and lessen the impact in a rear crash, and the way the SUVs now drive, all prove it was the right decision.
“It is segment-leading ride and handling compared to our competitors,” he said bluntly. “We make them look bad.”
Ford uses a five-link rear suspension in the Expedition comprised of two trailing links and three lateral links per side. Chevy has a four-link design using one very long trailing link and an equally long lower lateral link that carries the spring/damper mount and two upper lateral links, as well as coil springs and a stabilizer bar, all scaled to meet the grueling requirements of large SUVs while providing better ride isolation on rough surfaces and sharper handling response.
“I know ours is better. I have data that shows it’s better,” Herrick said. “Ford had to cobble it into their architecture whereas GM took a clean sheet of paper and drew it how [we] wanted it.”
The new chassis is designed to provide a smoother ride, especially on uneven pavement and unpaved roads because each rear wheel can handle road conditions separately. Aiding that effort is GM’s Magnetic Ride Control damping system as well as Air Ride Adaptive Suspension which is available on the top High Country and Z71 trim levels. Air Ride offers load leveling at all four corners of the SUV and can adjust the vehicle height by up to 4.0 inches.
GM’s T1 program started with the Silverado and Sierra light-duty pickups in the summer of 2018, followed by the heavy-duty pickups a year later. The 2021 Chevy Tahoe and Suburban will head to dealers in the spring of 2020.
The SUVs were planned to be different from the trucks from the start. Components no one sees could be shared, but anything the customer could see or touch had to be unique, including the instrument panels, seat coverings, panoramic roof, and the choice of nicer materials. Herrick said the SUVs share less than 25 percent of their components with the pickups.
The Chevy SUV family has also expanded, growing from three trim levels to six, based on consumer feedback that people like the different personalities of each trim. Pains were also taken to better differentiate the Chevy SUVs from the GMC Yukon and Yukon XL that we will see for the first time early next year. We also eagerly await the new Cadillac Escalade.