Modifying the FE4 (or FG2) Nivomat shocks for lowering springs

This modification allows one to retain the load leveling shocks that comes with the CTS-V when installing lowering springs. The principle is to lower the upper mount 1”, which allows the car to sit properly on 1” lowering springs. This retains the FULL travel of the shocks, and the bump stops, preventing damage to the Nivomats when potentially bottoming out. The alternative is to downgrade to non-load leveling CTS shocks, which have a much lower damping rate than the FE4 or FG2s.

NOTE: FE3 Nivomats on the CTS Lux Sport package have the upper plastic tube, spacer, and top pillow mount integral as one piece. I haven’t yet looked into modifying these, but if you have FE4 (CTS-V) shock parts (top pillow mount and plastic upper tube), they are interchangeable with the CTS parts. You simply disassemble both sets, and transfer the V parts to the FE3 shock with the spacers shown below.

To lower a CTS-V Nivomat self-leveling shock, one must lower the upper mount by a similar amount of drop that the springs will give. Otherwise the self-leveling mechanism in the shocks will pump up, raising the rear back to their designed as the ride height. This retains the stock Nivomat travel, since the top of the shock now sits 1” higher in the car.

Here are the steps to lowering the CTS-V Nivomats:

Stock Nivomat. Note the 1" rubber spacer below the top pillow mount. This is NOT the bumpstop. There is a very large bump stop inside the large plastic tube that covers the rod.

The stock Nivomat disassembled.

Here are the components of the spacers in the order they are installed. We’ve pulled out the stock spacer and will be putting new spacers above (and below) the top pillow mount. Note the small spacers that go inside the bottom of the top pillow mount to properly place the inner sleeve. A 0.2" rubber washer isolates the bottom of the top pillow mount during rebound, so there is no 'loose shock' clunk. Since the top pillow mount now sits 1" lower on the shock.

The first step after disassembly is to insert the small spacers over the stock sleeve and insert that into the bottom of the top pillow mount. Leave about 0.2" of the sleeve out of the bottom of the spacers and the top pillow mount, so the rubber washer (below) will slide onto the metal spacer tube.

Here is the sleeve with the small spacers inserted into the top pillow mount. After this slide a rubber washer onto the small (0.2”) left sticking out of the metal sleeve.

With the upper plastic tube cover on the shock body, slide the top pillow assembly (with new plastic spacers on the metal spacer tube) onto the shock.

Put the stack of larger spacers on top of the top pillow mount, followed by the stock washer and nut. Tighten until the nut bottoms out on the sleeve. I’ve installed with a hard spacer, two rubber, and another hard spacer. I think it would be better to have three hard spacers with a rubber one on top, to keep movement to a minimum.