2009 BMW Z4 - Chassis Secrets

Our friend Richard Aucock, who provided us with the behind the scenes article from the BMW Z4 International Launch, has a new article regarding the new roadster and its chassis secrets.

He is currently working on a few more articles from the Z4 launch, so I encourage you to follow him on his blog, as we will do the same.

Heinz Krusche is BMW’s chassis guru. I’ve met him several times, and always enjoyed top insight from him (not least his tales of how he keeps DSC turned on for the road – but ‘always’ turns it off when on track…).

Such people exist in every car company, but they don’t always have the power of Krusche.

He wields the same sort of influence as Jost Capito at Ford. There’s another genial genius – and look at how well Fords drive. Lotus, too, has Matt Becker, ensuring that every model drives sublimely.

So, speaking to Krusche is always enthusing. Here, then, are five reasons why the Z4 is another tick against his name.

1. Stiff Body In White
The basic bodyshell is 25 percent stiffer than before. Vital, said Krusche, for the entire driving experience. This torsional rigidity is the starting point, the vital gear in the cog. Without such a good starting point, he said, it is impossible to make cars drive well.

‘It is a big step down if the tolerances are too great.’ You can’t turn a fundamentally bad car into a good one with tweaks alone.

2. 3 Series front axle
The new Z4 uses the 2-joint front axle from the E90 3 Series (and also the various iterations of 1 Series). It’s vital, said Krusche, not least for improving feedback to steering.

With it, BMW can independently tune directional stability, steering feel and lane change stability. Curing a major flaw of the E85 Z4: its wearisome camber steer.

The rear axle, incidentally, is a development of the old Z4 (and is also on the X3). ‘There was no reason to change it,’ said Krusche.

3. Axially parallel layout electric power steering
The new Z4 also uses the axially-parallel EPAS system from the 3 Series. It means the engine isn’t sat on the steering column, so mass is reduced and a purer feel from the road is allowed. The electric motor is in parallel to the steering rack.