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Flex-a-form springs


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I'm thinking of replacing my Avanti's sagging leaf springs with the monoleafs from flex-a-form. For those of you who have done this before, can you offer any insights into your experience? Mark from Flex-a-form says that they can make these in a "high-arch" to give approximately standard ride height or a "low arch" for a 1.75" drop, and that their standard rate is about 200lb/in., althoughI can specify a stiffer rate if desired. This is just a street driven car so I'm not lookiing for something overly stiff. Thanks for any information.

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I have Flex-a-form leaf springs on my car. I used the standard application and have been quite happy with them.

They save a great deal of unsprung weight from the car which is always a good thing. The composite springs weigh about sixteen pounds for the pair against nearly one hundred pounds for steel. If there's a negative side for the composite springs, it's that they take the weight off the rear of the car instead of the front where the car is really heavy. For general street and pleasure driving that's ok but for any kind of "sporting" driving it should require ballast of some kind in the trunk to balance out the heavy front weight bias.

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Are you sure the springs are 200# per inch? That sounds really, really stiff for the rear of an Avanti.

Here's a quote from one web source:

"The suspension combines the heavy-duty coil springs of the Lark police car with the 5-leaf semi-elliptics of the station wagon. The rates at the wheels are 110 lb./in. at the front and 136 lb./in. at the rear."

If this is accurate, 200# would be 47% stiffer.

jack vines

Edited by PackardV8
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Here's the e-mail with the info I received from flex-a-form; it's the only information I have to go on so far. I guess I need to do some more research about spring rates.

Hi Adam,

We have used our “high arch” type of spring blank for approximately original ride height. Our “low arch” has about 1.75 in. lower free arch height for these springs.

The length dimensions are 20.5 inches front bolt centerline to axle centerline (center pin dim.) and 51 in overall (front to rear bolt). These are measured along the main arch of the spring. I don’t expect yours are different, but it’s a good idea to check especially since yours isn’t a Studebaker. These aren’t hard to check from under the car with a narrow flexible tape measure.

We have mostly made just over 200 lb/in spring rates going heavier for Avantis with high output engines.

Bolt sizes would need to be checked too but we wouldn’t need that info to get started.



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I checked with Mark at Flex-form about the spring rate, and he said that the rates between composite and steel springs are not directly comparable due to the additional friction steel springs have between the leaves and the difference in "compliance factor" of steel vs. composite. I'm not a spring engineer; I'm just passing along what I heard. I did do some more research on these springs and found that many owners of first gen Mustangs are using them. The 200 lb/in rate is being reported as firm but not too stiff.

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