“Can you feel how the shock absorbers are bottoming out?” Mustafa asks me to my left on the driver’s seat. Earlier on the freshly asphalted part of the country road everything was still okay. But here on the asphalt road with the bumps, the handling of the old BMW Z3 is actually anything but good. The roadster also quickly reaches its limits when cornering: “When it comes down to business, saying if the suspension has to work properly, you notice that the shock absorbers and springs no longer work optimally. This makes it rumble at the rear and the steering is also a little sloppy,” Mustafa explains.
No surprise, after all the BMW is now over 20 years old, built in 1998. Together with Daniel Boehnke, Mustafa Yavuz from our Customer Service / Technical Support wants to install a new suspension today to revive the proverbial driving pleasure of the Z3 and make the handling safe. The choice falls on the BILSTEIN B12 Pro-Kit, which offers a well-balanced sporty-comfortable set-up with maximum safety.
They take the car to the garage and up on the lift. Mustafa and Daniel first take care of the front axle. The two motor vehicle professionals dismantle the front wheels, loosen the tie rod and the bolts on the steering knuckles. After the screws of the dome bearings have been loosened, the struts can be removed.
A look at the old components shows: “The dome bearings are broken, the shock absorbers are externally ok”. But a simple test shows that the old shock absorbers are worn out and no longer serviceable. Mustafa compresses the standard two-pipe shock absorber, the piston rod remains in the retracted position and does not extend again. Mustafa has the explanation: “This is due to the nitrogen filling, which has evaporated. A problem that does not occur with our monotube technology”.
“On short journeys on level roads, the wear of the shock absorbers is hardly noticeable,” Mustafa knows. “However, in critical situations or on longer journeys they reach their limits more quickly because the nitrogen filling can no longer prevent cavitation (foaming of the shock absorber oil) and the characteristic of the shock absorber collapses. Due to foaming, the shock absorber loses its ability to damp the vibration energy by means of liquid friction. As a result, driving stability and driving comfort are impaired. “The best tires and brakes are of no use if the shock absorbers fail and traction is lost”.
The cover of the hood compartment on the rear must be removed so that the rear support bearings can be dismantled. The old shock absorbers and springs are quickly replaced. But the shock absorbers are not yet tightened. “The kingpin bolts are not tightened until the vehicle is back on the ground. Otherwise, tension can occur,” explains Mustafa. “In addition, when installing a new chassis, all axle bearings/rubber bearings should always be checked and the installation instructions followed”.
Once all the assembly work has been completed, the BMW Z3 goes where it belongs: on the country road. The 30 mm lowering suits the red roadster extremely well. Mustafa is satisfied: “The driving experience is much better now. The chassis now absorbs bumps, potholes or milled edges much more effectively”. How about the steering? “It also works much better, much more directly. All in all, the Z3 is sporty and comfortable, as if on rails”.
“Punching and swaying are perceived as typical driving characteristics of the old roadster,” Mustafa continues. “Our conversion to the BILSTEIN B12 Pro-Kit suspension proves that this image is unfounded, because the Z3 does not drive as one would assume. Agile and stable is the motto of our test. The BMW Z3 is running like a new car. No, I’m correcting myself, its handling performance is even better!”