DETROIT - Groupe Michelin wants to bring the cornering control of race cars to drivers everywhere.
The tire maker has developed an axle system that uses mechanically induced tire camber to optimize vehicle cornering, tire performance and comfort.
'By optimizing the contact patch, you are able to more fully utilize the potential adherence characteristics of the tire,' said Norman Frey, group leader for vehicle suspension analysis at Michelin Americas Research & Development Corp. 'It's always better to have more traction.'
The system, 'Project Ecco,' can work with any tire, Frey said. 'It's always a tire-vehicle system. You can't separate one from the other.'
Michelin unveiled the system at the SAE World Congress March 5.
Because Michelin lacks metal production, it needs the expertise of another supplier for the axle's structural components. 'We're wide open as far as how we're going to work out the fabrication of this when it gets into mass production,' Frey said.
The tire maker already has a relationship with French metal parts maker Groupe Vallourec. The two linked in 1999 to develop suspension system products.
Last year they introduced EVAX, a hollow tube axle that uses natural rubber bushings to take up the torsion forces and act as springs in the system.
Michelin wouldn't say how much it invested in the Ecco project, but it dedicated many engineering resources in the past 18 months. The rear axle system is being tested on an unspecified European coupe. It also could be used in front-end applications, Frey said, but packaging would be more difficult.
Similar to standard suspensions, Ecco is a short and long control arm system. Unlike conventional assemblies, it uses linkages that allow the vehicle's tires to roll off vertical center automatically in a turn, while retaining a position perpendicular to the road on straights.
Using negative camber to increase cornering force is not new. Race cars have long used negatively cambered rear tires, tilted in at the tops.
'They do that to help compensate for the tread pattern that is developed when you're in a corner,' Frey said.
'You want to have the ability to generate cornering force at the rear of the car for stability.'
As a vehicle goes into a turn, centrifugal force pushes the vehicle's weight to the shoulder of the tires on the outside of the turn. That force leans the cambered tire in to the turn - much like a motorcycle does - making the tires perpendicular to the road once more and allowing them to attain maximum adherence or traction and an optimal, square-shaped contact patch.
Without proper camber, tire contact patches are distorted to a triangular shape.
The areas absorbing contact stress are greatly decreased, which means wear and heat in those areas increase, Frey said.
Stress on the contact patch is more evenly distributed with the induced tire camber or tilt of the Ecco system. This increases potential grip and cornering force by as much as 10 percent to 15 percent, he said, depending on the profile of the tire, inflation pressure and the change in loads because of suspension and vehicle design.
'Anything that you do to a suspension system that improves the durability of the tire - which is both tread wear and structural integrity - is good for the buying public,' said Jacques Bajer, president of Tire Systems Engineering Inc., a Grosse Pointe, Mich., consultancy.
Ecco uses kinematic linkages in the axle to camber the tires automatically into turns and keep them perpendicular to the road on straight paths, giving drivers of vehicles equipped with the systems the best of both worlds, Frey said.
Ecco also enhances passenger comfort by enabling the tire to absorb shock better while encountering bumps during turns, he said.
'This (Ecco) system that we have is 100 percent passive. There's no semi-active component to it,' Frey said.
The system relies fully on mechanical components, he said. There are no electronics or sensors to fail, and therefore no additional cost and no maintenance required for the system.
'It's like a conventional suspension, except it has a breakthrough concept,' Frey said.
'The concept looks fundamentally sound, but its execution in production must be consistently precise,' Bajer said. 'That's commendable if they (Michelin) can do it.'