This article was first published in 2004.
Current Holden Special Vehicles are superbly
sorted in their real-world ride/handling abilities. Unlike some overtly sporting
cars, the suspension has been set up to cope with off-camber corners, with
bumps, with occasional potholes. But these are cars that on smooth roads also
handle very well indeed. Underpinning these outcomes must be a specific
engineering development philosophy - it's sure not something which is arrived at
To find out what makes HSV suspension happen, we
talked to suspension engineer Mark Beasy and engineering manager John Clark. It
was a wide-ranging discussion that also covered some aspects of aftermarket
What is suspension engineer Mark Beasy attempting
to achieve when he develops the suspension on an HSV model? What does he like
about a good-handling car?
"During the development I drive in several
different driving styles to get the car balanced for a variety of different
customers," he said.
"I like a car with a smidge of understeer - but
not too much, I am not a fan of loads of understeer because the average customer
is not going to get onto the power to balance the car.
to get on the brakes to slow the car down.
"Also, it's important that the car's not too
reactive, so that anyone can get in and drive it. And drive it fairly hard and
be fairly rough and still get away with it, while having loads of fun."
John Clark added that the cars were set up to be
stable, even with late braking into a corner. He said that the rear toe link had
been a big advantage to HSV in that it allowed better control of the rear
suspension. Having the front and rear damping set so that the cars pitched less
also gave advantages over successive waves of bumps.
"The pitch control keeps the cars having a very
level feel," John said.
Keeping lateral stability is also important, and
damping plays a large part in this. Mark said trying to control the roll centre
and how the car reacts with the damping was critical in the cars.
"If you haven't got enough rebound on the front,
you turn in and the front will lift, because the roll centre shoots out there
somewhere," said Mark gesturing at the far wall.
"So immediately that loads up the rear, and as
soon as you turn in, bang! you get oversteer."
HSV use 'digressive' damping, where the rate of
increase in damping versus piston velocity is non-linear.
"As you go higher in piston velocity, instead of
just going higher and higher in compression force, it actually decays off and
becomes flatter on the graph," Mark said. "The benefit is that when you hit a
big bump, you don't get that shock coming through the car. The car is more
compliant. You can't just go stiff and expect the car to have grip."
Shown on this damper dyno graph are the VX (red)
and the VY (green) dampers. It can be seen that in the later model dampers, at
higher bump shaft velocities the damping force gets stronger at a slower rate
than with the previous model dampers.
The engineers said HSV spend a lot of time
matching the suspension to the tyres. They said that the type of tyre selected
played a critical role in determining the understeer/oversteer balance.
"I always knew that the tyre manufacturers could
alter the construction of the tyre to alter the understeer/oversteer balance. I
knew they could - but I'd never experienced it until recently. But then I got a
set of tyres that could
turn the car into big understeer..."
But if the marriage between specific tyres and a
specific suspension tune is so vital, what about those customers who change the
tyres on their HSV models? Engineering manager John Clark said that in his
experience, this seldom happened.
"You can make a car diabolically dangerous by
putting the wrong tyres on it," added Mark.
HSV don't use any plastic bushes in their
suspension revisions - in fact, they keep the standard Holden bushes throughout.
But when the aftermarket has a love affair with plastic replacement bushes, why
don't HSV use them?
"We don't want to have feedback through the
steering column or the cabin space," John said.
He also said HSV had found durability problems
with plastic bushes, problems the traditional rubber bushes didn't have. He said
people didn't realise the complexity of the standard bushes.
"People think that it's a rubber moulded bush -
and that's it. But the bushes in our cars have voids in certain areas to control
movement in different ways."
Mark said the rear suspension design used on the
Holdens was a classic example of where voided bushes needed to be used. He said
the bush allowed a fore-aft movement to take place. Without the voided bush, the
suspension arms would be fighting each other as the wheel went through its
"It would actually bind-up if it was a solid
bush," Mark said.
He said by the use of voided bushes you could more
strongly control the impact in one direction versus another.
Sway bars are widely used in the aftermarket as a
suspension fix. What do the two engineers think of this simple bolt-on approach?
John said a car with bigger sway bars turns in
nicely but can be very skatey.
"The actual grip of the tyres will be reduced. You
may feel as if you're going quicker but if you get interruptions part way
through a corner (like a bump), it will tend to really unsettle the car."
"You're loading the outside tyre more so your
inside tyre's not doing the work," Mark added. "My experience - outside of HSV -
is that when you get an aftermarket suspension and actually compare it
back-to-back with what you had originally, nine times out of ten you'll find
that you're not as quick."
AutoSpeed's recent test of the Nissan 350Z has
attracted worldwide attention. Basically, on real world Australian roads we
thought the car lacked grip and handled poorly, although on smooth racetrack
style surfaces it could work very well. The HSV engineers have driven the 350Z -
what did they think of it?
"It had bad axle tramp and it was just miles too
stiff," said Mark. He said he and another suspension engineer went out in the
car for about two hours - and that was enough.
"It handles quite well," Mark said. "Lots of
understeer on tight corners, though. But for a road car the ride was terrible.
You'd put it on the trailer, you'd drive it to the racetrack, you'd drive it
around the track and you'd put it back on the trailer."
But John Clark said the way the car was set up may
have been the Japanese engineer's brief and that it may suit Japanese roads and
The Holden Monaro and the HSV
One car where we were unimpressed by the
suspension is the Holden Monaro. But the HSV Coupe - nearly the same car but
with revised suspension and steering ratio - we thought was very good. How did
Holden get the two-door wrong and HSV get it right?
"The Coupe is actually quite a difficult car to
tune the suspension in," Mark said.
"But once you get the Coupe just right - whether
it's a luxury touring or a performance suspension - you can transfer that into a
sedan. But if you develop a suspension for a sedan, it's highly unlikely that it
will work in a Coupe because the transfer from the front wheels to the back
wheels when you hit a bump
is so much faster."
But if the Coupe has the same wheelbase as the
sedan, why are bumps transferred more quickly?
"The torsional rigidity on a Coupe is actually
quite high," John said. "It's up over the sedan by about 40 per cent. When you
turn in, the response front-to-rear gives it quite a different feel."
The engineers said that it was the altered
torsional rigidity of the two-door over the sedan which had caused Holden to
slow the steering ratio of the Monaro. This contrasts with discussion at the
time which suggested it was the altered weight distribution of the
shorter-tailed Monaro body.