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Mangusta Rear Frame Modifications - September 2009

MANGUSTA REAR FRAME MODIFICATIONS:  The results
By: Dick Ruzzin

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I have driven my car for over 500 miles now with the changes to the rear frame and can now tell you the results that I am experiencing.  I think if you have a Mangusta this experiment will be interesting to you.  My cars Koni shocks were recently rebuilt and I also have new motor mounts, both made a big difference in the cars handling.
I have noticed that the Pantera has a similar soft mounted rear bridge.

Basically a new rear bridge was made from a square tube of thin steel, it is bolted in at the top of the frame and it forms a solid box at the rear, complementing the welded in bottom structure that carries the lower A-arms ball joints.  The new bridge forms a solid structure from the upper ball joint for the right wheel through the bridge to the upper ball joint for the left wheel.  The ZF hangs from the new bridge by three internal rubber bushings. This is the very opposite of the original configuration where the ZF is solidly bolted to the bridge and the bridge is soft mounted to the right and left sides of the frame.  The flexible small rubber mounts and their attachments allow the flex in the frame that has been written about for years.

 The original soft mounted bridge is the link between the upper rear links on the right and left that goes directly from the top of the hub carriers to the frame.  Because both of the original bridges are held in place by single long bolts on each side they act as hinges, allowing the frame on each side to lean from right to left during cornering and directly affecting the rear wheel camber.

The ZF has two bosses that were bolted solidly to the old bridge.  These two bosses have been encased in a new bushing retainer that fits tightly inside the new bridge to avoid twisting.  It carries three long pressed in rubber bushings and is held in the new bridge by bolts.  The new bridge is solidly bolted to the frame and the ZF is mounted to it through the flexible rubber bushings.  All the new bolts are shoulder bolts going through tight fitting welded in tubes.

EFFECT OF THE CHANGES:

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1) The car feels much more solid than before, my original bridge bushings were very worn so I expected an improvement.   My Mangusta, and I expect others also, felt tail-heavy unless the fuel tank was almost empty.  I found that 32 pounds of air in the front and 35 pounds in the rear gave the best feeling of balance, especially at higher speeds.

3) I have just filled the gas tank, I never ran with more than 1/2 a tank before.  It was not until I arrived home, 20 freeway miles later that it dawned on me that the trip was without tail-wagging or special attention on curves.

All of these changes were conceived and executed by Werner Meier, a former GM engineer who has a well known and respected Corvette restoration shop called MASTERWORKS in Madison Heights MI.