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The officials at American Axle & Manufacturing Holdings, Inc. weren't quite finished their presentation, but Bob Lutz had heard enough. General Motors' vice-chairman was visiting AAM's Detroit engineering center recently to review the supplier's future chassis systems. Accompanied by GM T800 program boss Terry Wochowski, Lutz was shown a new independent rear suspension (IRS) module that can be bolted straight into General Motors' full-size SUVs and pickups.

Prestol An IRS in place of a live axle, installed in line sequence. It's called I-Ride, and requires no changes to the bill of process.

AAM chief engineer Dan Sagady waited for Lutz's reaction. Dick Dauch, AAM's chairman, watched the faces of the two GM executives.

Lutz turned to Wochowski. "Why aren't we doing this?" he asked. "It makes so much sense."

That's music to the ears of Dauch and other chassis-systems suppliers. With OEMs targeting "car-like" ride and handling for their future SUVs and pickups, suppliers are touting the advantages of IRS combined with 4-wheel steering (4WS). MM, Dana Corp., ZF North America, ArvinMeritor, Delphi Automotive Systems, TRW Inc. and Magna Corp. are readying new bolt-in module designs for customer review. The most sophisticated of these integrate rear-wheel steering hardware and electronics into an IRS unit.

Delphi's Quadrasteer, introduced on '02 Chevrolet Silverado and GMC Sierra pickups, performs superbly. But cost is high (a +$4,000 option) and it's based on a live axle.

Competitors believe they can do better. AAM, which has already won the axle business for GM'S 2005 T900 program, aims to beat Delphi with "a higher-value, lower mass 4WS," notes Sagady.

But while the competition chases the rear steer market for light trucks, Delphi has taken the concept one step further. It's Unified Chassis System (UCC) integrates electric-powered rear steer with TraXXar controlled-braking. Integrating the systems electronically allows them to compliment each other.

And IRS applications are expanding beyond luxury German and Japanese sport-utes. Ford has designed it into the '02 Explorer, Mountaineer and upcoming Lincoln Aviator. Ford is also considering a bolt-in IRS for its hot-rod SVT trucks.

"There's no question that IRS gives a tangible benefit to on-road handling, should engineers choose to take advantage of it," says Aaron Robinson, technical editor of Car and Driver magazine in Ann Arbor, Mich. "And it offers better packaging for a third seat row." But he notes the tradeoffs with IRS are limited off-road capability and higher cost, versus a live axle.

ArvinMeritor designed its IRS concept without any request by an automaker and did it in only nine months, says Robert P. Carlstedt, vice president, suspension module engineering.

Instead ArvinMeritor worked with several key suppliers to develop the system, which like AAM's IRS, can be supplied in line sequence for virtually any full size light truck or SUV. (It will be shipped with its shock absorbers and springs included in the crate.)

"The integration capability is what is really important," Carlstedt says.

The supplier took on the project so it would have the IRS expertise when a customer came calling. Now it has a system ready to go if and when an automaker wants to switch over to an IRS.

"We don't want our customers to be our learning ground," Carlstedt says.

ArvinMeritor's IRS is much like its competitors with a multi-link suspension, four-wheel steer capability and adaptive ride, in a modular design. It can be installed on the same assembly line as existing live axle suspensions and major attachment points are nearly common, says ArvinMeritor.

Next ArvinMeritor will begin shopping its system to potential customers. The concept is currently installed on a Yukon Denali, which currently does not have a production IRS.

# posted by Medical Information : 3:43 AM