|NEWEST ANGLE of Chevrolet styling for
1958 is seen from the rear. Basic shape of
body is much like design that preceded it.
LAVISH USE OF CHROME on front end is characteristic of all GM styling for '58. Dual headlamps are standard on all series.
|REMEMBER when Chevrolet was
strictly a "transportation" car, offering little in the way of performance, styling or engineering to, capture the imagination of automobile fanciers? It was dependable, economical, but definitely not exciting. Just how much this situation has changed was demonstrated vividly by the 1958 Bel Air Impala tested for this report!|
This model was selected for testing because it is a brand-new one in theChevy lineup and was equipped with the new 348-Cubic-inch V-8 and air suspension.
Like all 1958 models it had an X-shaped frame completely different from past Chevrolets. As the foundation for the entire car, this frame design is one of the more important engineering features of the new Chevy.
As the name implies, the new frame is shaped like a big X. It does not have parallel side rails joined ladder-fashion by cross members as in conventional designs. From a reinforced box girder center beam box girder side rails splay out to the front and rear corners of the car.
The arms of the X are joined at front by a box section front suspension cross member and at rear by a channel section cross member.|
As mentioned, the test car had Chevy's new Level-Air suspension. This optional air suspension (priced at $115) uses air springs at each wheel in place of the standard steel coil springs.
In either case a brand new rear suspension arrangement is used. The familiar semi-elliptic leaf spring setup has been replaced by a four-Iink trailing arm design using either coil springs or air bags. Lower control arms run from each side of the rear axle to mounting hangers set on frame side rails just back of the pinch-in center frame section. These arms receive both the vertical force of highway bumps and braking and driving thrust of the axle.
A single U-shaped upper control arm is pivotally mounted at the rear axle housing and curves up to frame attaching points. This arm controls lateral stability, restricts driveline and axle windup.
The new frame and suspension design results in a higher roll center and lower center of gravity, so Chevrolet was able to soften ride without loss of stability.
How about handling? Extensive cornering checks brought out the fact that the Impala has excellent roadability for such a soft-riding automobile. It might be a shade behind steel sprung 1958 Chevrolets in this respect, but the slight loss in handling is compensated by improved ride -- or such will likely be the attitude of most buyers.
Most impressive single advantage of air suspension is that rebounding after a bump is completely eliminated. The Impala would settle right back to nomal immediately after absorbing a road shock with none of the continuing up and down motion found in steel sprung cars.
Another important air suspension feature, of course, is the car stays level and at a constant height. An unusual thing about the Chevy system is that height control valves are located inside air spring domes -- one in each front unit and one in the left rear unit.
There are several quirks about these air suspension cars owners will do well to remember. A shut-off valve on the air lines junction block must be closed when an air suspended Chevy is raised on a frame contact hoist or by bumper jack. Otherwise all air in the system will be exhausted. The same thing must be done when the car is towed or pushed with the engine not running. The junction block on which the valve is located is mounted on the left frame rail just back of the air accumulaton tank. All 1958 Chevrolet owners must also be careful that service station attendants make sure they have proper adapters on the frame contact hoists before attempting to raise one of these cars.
Like 1957 Cadillacs, new Chevrolets can't be raised on regular H-type hoists without adapters which contact the X-shaped frame members. Undoubtedly some new models will be damaged by unthinking attempts to raise them on standard hoists!