Chrysler Torsion Bar Suspensions (and Leaf Springs)

Chrysler used torsion-bar suspensions for all its cars from 1957 until well into the front-drive era, from the lowly Valiant to the top-range Imperial. They were first adapted to Chrysler by Bob Batchelor; they had also been used in European cars and the Cadillac Eldorado / Oldsmobile Toronado.

torsion bars

There were many torsion-bar snapping problems in 1957, when the systems first launched, but by 1958, Chrysler had mostly resolved the problem.

In addition to the torsion bars, the company used an anti-sway bar (often just called “sway bar”) to resist lean in turns, with various degrees of success depending on its thickness and the suspension tuning; generally, Chrysler Corp products had less body roll than equivalent GM or Ford cars. Diagonally mounted steel struts reinforced and positioned the front-wheel lower control arms.

In back, widely spaced, off-center mounted rear leaf springs cut acceleration squat and brake dive; the pairing of cheap leaf springs with front torsion bars remained unusual through the system’s life.

axle

In newer versions, used in the 1970s and later, the upper control arm had a front pivot higher than its rear pivot instead of at equal height, so that weight shifts forward when the brakes are applied, helping to keep the car level. The off center leaf springs, with the rear axle mounted on the thick forward sections of the springs instead of on the centers, were set up so that the stiffer forward sections of the springs would support the body during acceleration and braking shifts; having long, flexible portions behind the axle benefited the ride.

Leaf springs were, at the time, hailed for better good at adjusting to varying loads: lighter loads were handled by the long, flexible leaves, and heavier loads by the short, stronger leaves.

leaf springs

The front end of the torsion bar connected to the front wheel’s lower control arm; the rear end of the torsion bar was anchored in the sub frame so the bar could not turn. When the front wheel rose over a bump, the lower control arm pivoted around the points where the torsion bar was mounted, twisting the bar. The chromium steel in the bar resisted the twist, holding the wheel on the road.

torsion bars

The system allowed tuners to easily raise or lower the front end of the car by adjusting the torsion bars.

The related Torsion-Quiet system described rubber cushions which isolated the subframe and leaf springs, reducing vibration and noise the same way that rubber engine mounts do. The problem, though, is that as isolation was added, stiffness was necessarily and by definition reduced, so that cornering was degraded.

torsion-quiet

For decades, using torsion bars rather than the systems used by GM and Ford on most of their vehicles helped Chrysler to have a smoother ride with better cornering than they would have with a more conventional (given the times and costs) system. Through the years, Chrysler vehicles tended to corner better than their domestic counterparts - or felt better.

The company went to other designs as technologies changed. The advantages of torsion bars were eventually outweighed by the tradeoff between noise, vibration, and harshness on one hand, and cornering capabilities on the other. The more isolation was added, the worse the cornering would be. There was also the issue of unsprung weight, solved by fully independent suspensions, which could also do better at maintaining full traction at all four wheels on bad roads.

“Dana44” wrote:

One trick with the leaf springs is to angle them. If the front eyelet attachments are two inches (one inch each) closer together in the front, and the rear eyelet remains stock, the torional twist of the offset which improves handling. For example, if the front eyelets are 58 inches between the two front eyelets, the rear are 60 inches between the two eyelets, not only do the springs now flex up and down, but they also twist a little bit when they go up and down, which improves cornering.

Coils take up less room, give ability to lower car and drop center of gravity lower, less engineering required for the package, and ability to move rear wheels farther to the rear corner of the vehicle. Additionally, the MacPherson strut design adds coil spring and shock together to eliminate parts, but to get them to handle as well as leaf springs, the ride gets rough, so it is a tradeoff.

Tannon Weber pointed out:

Unsprung weight is a disadvantage, and with the leaf springs, the axle is unsprung. There were vehicles with coil springs in the back that had traditional live axles, like several mid-sized GMs. You have to go true independent to reduce unsprung weight.

Some companies like Alfa Romeo really got away from unsprung weight — there were models where the brakes were up against the differential before the CV shafts, so that there was even less weight at the hubs.

There is an advantage in a driveline where one doesn’t have to work with pinion angles and other driveshaft geometry because the differential is attached at the body. But, doing maintenance is a lot harder too, as changing out shocks is hard.

See transverse-mounted torsion bars.

Here’s a color cutaway showing some of these components:

1975 Chrysler drawing

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