A comparison of Intrax and Eibach rear springs on the 1995 Saab 900 convertible.

Intrax springs have a barrel design, where it has a number of softer coils which are always fully compressed to compensate for a shorter length and provide some preload when the car is up in the air. The downside is that there's only a couple of coils left uncompressed, which limits the suspension travel, and the ride suffers a lot. Eibach, on the other hand, uses a progressive design, where the thickess and stiffness of the coils varies through the spring length. It employs all of the coils at various stages of the suspension travel, which allows for a much more comfortable ride without having to make the spring too soft to sacrifice the handling.


You can see how the spring is almost fully tight under the weight of the car, except for the last coil. There's virtually no room for the spring to compress further, which means the car will bottom out on every bump.
Bump stop

Here's a new trick for removing the bump stop, suggested by Jose De Jesus. Compress the rubber piece with a hose clamp, spray it with some soap water, and it pops right out.
Off the car

The differences in the spring design are apparent from this picture. The quality differs a lot too - both springs were on the car for about a year. The Intrax is all rusted and peeling, while the Eibach still looks like new.

A new spring installed (the installation procedure is described in this article). From the looks of it, it appears that the ride is going to be much more comfortable.

Installation complete. The ride height looks just perfect.
Intrax vs Eibach

Here's a direct comparison of both springs installed in the same corner.

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