Mazda3 drills into your mind

This is going to sound a bit loopy but here goes… Mazda made the seemingly retrograde step back from independent rear suspension to a simpler torsion beam for the new Mazda3, after it drilled into the human subconscious!

Yeah we know it sounds a bit loopy, as well as kinda icky and invasive, but there was no blood and gore involved -- just a whole lot of research and data compilation.

Essentially, it’s all part of Mazda’s new human-centric vehicle development process that debuts with the fourth generation Mazda3.

The originator of the human-centric philosophy is Mazda’s senior dynamics engineer, Yasuyoshi Mushitani. He identified the simpler torsion beam as a key to improving the ride and body control of the Mazda3, without sacrificing its nimble handling qualities.

If you reckon that sounds counter-intuitive don’t worry, plenty of people at Mazda felt the same way. Traditionally, independent rear suspension set-ups have been considered superior.

“When they said we are going to use torsion beam I said: ‘it’s not going to work’,” Dave Coleman, the manager of vehicle dynamics at Mazda R&D in North America told carsales.

“I know what it’s like to not believe it’s going to work.

“Mushitani had this idea figured out well before any of us believed him. There was a long process of us going ‘are you sure this is going to work?’. Once we had prototypes [however] we settled down quickly and realised it was going to be fine.

“But we were certainly nervous for a while,” Coleman confided.

Coleman was speaking at the global launch drive of the fourth generation Mazda3, which goes on sale in Australia mid-year. The new hatch and sedan range is expected to rise in price and equipment levels.

In search of a more premium car, Coleman says Mazda abandoned its traditional way of tuning suspension by measuring the amount of energy entering the cabin. Instead it focussed on the reaction of passengers to bumps.

“We were seeing there wasn’t really a direct correlation between energy and how someone was reacting,” Coleman explained.

“We filmed a car going over a bump and watched the driver’s head, because the main thing your brain and subconscious are doing is balancing your big fat head on your little neck as you move around. You can see if something was judged wrong in the motion of the head.

“And we saw in some of our older cars that even if objectively they seemed to ride well you’d go over a bump and see the driver’s head move a surprising amount,” Coleman revealed.

Those lessons define the new Mazda3’s suspension design and tuning process.

“This is the fundamental thing that drives all the suspension decisions from there out,” Coleman explained.

“The need to have a more simple input coming into the car drove us to more simple suspension structures that we can tune more precisely.

So, the torsion beam with one bushing per corner replaces the third generation Mazda3’s E-Link with seven bushings. Up front, the MacPherson strut has also been simplified. That allows preciser tuning, a simpler movement and, Coleman says, a better ride.

And guess what? It’s actually stiffer!

“If we simplify the motions and we have a single diagonal input from each bump we can stiffen it up and have a firmer suspension and still no-one complains about the ride. That’s the magic of starting from the human subconscious and building outwards. You find little gems like that.”

Coleman is now a staunch defender of the torsion beam, which only a minority of small cars still use.

“There is some confusion on the independent versus beam thing,” he said.

“The torsion beam is kinda independent, moreso than a solid axle. The connection is up near the pivot. It’s basically just a really big sway bar. In terms of wheel motion over a bump it is really independent.

“But in cornering some of the load goes across to the bushing on the other side, so it’s sort of semi-independent.”

Of course, there are other reasons like cost (and space efficiency) for going to a torsion beam. And there are other contributors to the new Mazda3’s dynamic behaviour like its more rigid body in white, that in turn allows a more compliant tyre design, a new in-house steering rack and further development of the company’s G-Vectoring Control which ‘tunes’ available torque to maximise steering response.

There are also some minor suspension tweaks between different markets, including Australia. But Coleman insists our subconscious is the key to it all.

“We are not going for what people think what they want,” Coleman says.

“We are tuning for the subconscious. That is universal.

“Once you understand the basic fundamental subconscious, it doesn’t vary by market, it doesn’t vary by what you’re into… It’s just a completely fundamental thing,” he stated.