Wednesday, September 29, 2010

Examining the Fiat 500's Suspension

The Fiat 500 is built on the Fiat Panda's chassis and shares its suspension. The 500 has the same wheelbase as the Panda but employs wider tracks and a lower roof to improve handling.

The 500 has a "McPherson strut" front suspension and a torsion beam rear axle designed by Magnetti Marelli. This tried and tested configuration has been around for many years but has been refined for use in the 500.

Let's explore some of the details of the 500's suspension. Please note this describes the European version, but the US model is expected to use the same type with some slight tuning changes.

The Fiat Strut
As mentioned above, the front suspension is the type commonly referred to as the MacPherson strut, named after a Ford engineer who popularized the design in the late 1940's early 1950's.

However, Fiat engineers had patented this type of strut suspension in 1927. The only difference between the Fiat design and the MacPherson design was Ford's use of the sway bar to provide some degree of horizontal compliance, in conjunction with an I-shaped lower control arm.

The Fiat design used a separate sway bar and an A-shaped lower control arm.

The Fiat way of anchoring the control arm actually offers a more precise way of locating the wheels during suspension movement.

The Fiat 500 has a refined version of "The Fiat Strut" with the main difference being the use of an L-shaped lower control arm.

Details that bring this suspension into the 21st century

The Fiat 500 features a coil spring design that increases the absorption of minor surface roughness. These offset coil springs reduce side load forces acting on the strut with resulting improved absorption of slight unevenness in the road surface.

The Fiat 500 uses ductile iron control arms

Also featured are lower control arms made from ductile iron (not cheap stamped steel) with a new style bushing fitted on a vertical axis at the rear to improve the absorption of vibrations and increase road holding when cornering.

The Toyota Yaris uses cheaper stamped steel control arms typical of inexpensive cars

In contrast. the above is a control arm from a Toyota Yaris (a car that some may compare to the Fiat 500, but although similar in size, is not in the same league as the 500). Not a bad car, but the Yaris is a typical econo-car which features the usual cost cutting engineering such as cheap stamped steel control arms. Engineering details like this separate the 500 from common sub-compact cars most Americans are used to.
Sub-frame mount on left. Special control arm mount on right

The suspension sub-frame is attached to the body of the car without the use of rubber isolators. This crossmember is made from galvanized steel to guarantee improved resistance to structural corrosion and has been strengthened with box sections where it attaches to the body to ensure better filtration of the noise entering the passenger compartment.

The telescopic hydraulic shock absorbers are dual-acting and...

Upper strut mount tuned for ride comfort

...the upper strut mount has optimized axial rigidity to improve comfort.

To improve cornering, the wheel strut's geometry has been designed to maintain a better camber angle during turns. This keeps the wheel closer to perpendicular to the road.

Lower mount for the front sway bar endlink uses ball jointed sockets...

Notable on the front suspension is the way the anti roll bar end link is attached to the strut with ball jointed sockets. does the upper mount for the sway bar end link. Typical of more expensive cars.

This type of end link is usually reserved for higher priced cars and boasts a greater ability to filter out vibrations when driving over rough roads.

Looking at the rear
Left side view of the rear torsion beam axle. Notice the orange elastomer bump stop. More expensive and higher tech than a traditional rubber bump stop, the elastomer bump stop is used as a spring medium and allows the springs to be softer for a better ride when lightly loaded.. They come into play when the car is heavily loaded or hits a large bump, progressively cushioning the impact and again helping the ride.

In the rear, the compact, torsion beam axle functions both as wheel locating arm and as an anti-roll bar to resist lateral motion of the wheels as the body leans in turns.

Other characteristics of the rear suspension are:

Greater comfort because the level of noise and vibration entering the passenger compartment is lower due to single (metal and rubber) bushings attaching the rear axle to the body.

On the rear of the Fiat 500. Notice how the shock absorber leans forward and not straight up. This keeps the shock from intruding into the trunk area and limiting the trunks width.

An optimized underfloor shock absorber angle that locates the shock beneath the floor to improve comfort without detracting from trunk space.

The rear of the Toyota Yaris. Notice how the shock sticks nearly straight up, encroaching on rear trunk space. Compare the angle to the Fiat's

The above is the rear suspension from the Toyota Yaris. Notice how the rear shock absorber is near vertical. Compare this with the Fiat 500 rear shock angle. The Toyota design intrudes into the trunk, narrowing its width. The Fiat design doesn't intrude into the trunk, maximizes space, and is an example of Fiat's acknowledged small car design leadership.

Rear Axle beam bushing provides toe-in effect during cornering, providing increased stability

Greater driving stability due to the bushings attaching the rear axle to the body. While cornering, they generate a wheel toe-in effect that ensures excellent driving stability even under difficult conditions. They also display great longitudinal flexibility when hitting bumps.

Handling is improved because the folded sheet steel torsion beams torsional rigidity has been tuned to provide balance between front and rear.

Starting in December 2009, all Fiat 500 sedans have a rear sway bar fitted, improving the ride and handling

New Suspension Upgrade with improved ride comfort

From December 2009, all Fiat 500s have a rear antiroll bar installed. With this addition, Fiat has been able to soften the spring rates and improve the ride of the 500. This addresses the one criticism that had been leveled on previous versions of the 500 (keep this in mind when you read older European road tests on the 500. When a review mentions the ride, they are talking about the older car).

Previously, the rear torsion beam axle was tuned to act as an anti-roll bar. The slight increase in weight of the new sway bar is offset by the improved comfort. Handling has, by all accounts, been improved.

It should be noted that the Fiat 500C and the 500 Abarth had the rear anti-roll bar from the start of their production.

Here's an excerpt of the Fiat tech bulletin provided to UK Fiat dealers:

"Starting with the production of the new MultiJet engine, all Fiat 500’s will be fitted with the stabilizer bar which was already introduced with the Fiat 500C. The anti-roll bar is a 21mm diameter solid steel bar, fixed to the crossmember using brackets made from a single piece of steel and part in rubber. This represents a quality intervention designed to improve the comfort and the handling of the car with a far more absorbent ride quality as you’ve experience in the Fiat 500Cs."


Although it is possible to get manual steering in some countries in Europe, most models of the Fiat 500 have electric power steering called DualDrive.

This innovative, speed-sensitive power steering system, comes with two operating modes and uses an electric motor, rather than a hydraulic pump driven by the engine, which results in a considerable reduction in both fuel consumption and noise.

The system offers a choice of two settings via a button on the dash marked "City".

The normal setting (off) ensures maximum feedback and driver involvement.

Pressing the "City" button lightens the steering to minimize effort, and is therefore ideal for urban driving and low speed maneuvering.

To ensure maximum safety under all driving conditions, both settings offer identical power assistance over 44 mph, thus ensuring a steering wheel response suited to high speed driving.

Additionally, the 1.4-liter Sport model has a "Sport" button in place of the "City" button and, when activated, provides increased steering effort and sharpened throttle response.

500 Abarth changes

The Abarth’s suspension is firmer and 15mm lower than the standard 500. A Rear anti-roll bar has always been standard.

The popular 500 Abarth Essesse kit adds the following:

17-inch alloy wheels, stiffer suspension setup, an additional 5 mm lower ride height, cross-drilled brake discs and upgraded pads.

Also featured in the Esseesse kit, the 1.4-liter turbo engine gets higher boost due to revised ECU and a less restricted air filter. Max power has increased by 25hp to 160hp, while max torque is lifted from 152 to 170 lb-ft.

References: The New Fiat Guide by Jan P Norbye 1969, Fiat 500 E Learn Manual, Fiat Group Press


peterjerome said...

For anyone that has access to the magazine "Car" from England, there is a very comrehensive and positive article on the Twin Air 900cc engine in the 84 hp Turbo configuration. It is in the September edition which should be on the racks in North America right now. There is also a feature on Gordon Murray's city car (T25) which really should be powered by the TwinAir. Mr. Murray owned five FIAT 500s (nuova) at one time.

Anonymous said...

Very well written.

I love reading technical stuff like these.
Provides a lot more insight into the 500.

Thanks. said...

Anonymous said...
"Very well written.

I love reading technical stuff like these.
Provides a lot more insight into the 500."

I love technical stuff, too. My goal is to bring a lot more technical descriptions and features of the 500 to this site once the US model is introduced and I can gain access to the material.

Keep an eye out for it....

Thanks for following and best regards, Chris said...

peterjerome said...
"For anyone that has access to the magazine "Car" from England, there is a very comrehensive and positive article on the Twin Air 900cc engine in the 84 hp Turbo configuration. It is in the September edition which should be on the racks in North America right now. There is also a feature on Gordon Murray's city car (T25) which really should be powered by the TwinAir. Mr. Murray owned five FIAT 500s (nuova) at one time."

Thanks for the heads up on that article. I'll have to check it out.

Best regards, Chris

Anonymous said...

I wish to GOD Fiat made this a fully independent rear suspension. Its such a waste of a potentially great car!