funky steering!

[Icecold]

not sure if this is normal but here goes,

as you guys know i have just picked up the car and it drives beautifully and handles great but, there seems to be an issue with the steering. from what ive been told, the e39 540i sport has a recirculating ball type of steering(what ever that is!) and every time i floor it the steering wheel stiffens up to the point of not being able to turn it beyond a small distance. is this normal?? some sort of safety thing or is it "mashup!!"

it steers very smoothly when i'm driving normally so im a bit confused!

any ideas?

[peppernick]

Shouldn't be that case at all. The recirculating ball steering (lack of space in the 540) is less communicative (not as immediate as the rack and pinion of 6pot cars), but you shouldn't have to work that hard to move the steering wheel! You need to have it checked out, sounds dangerous.

[BigFas]

Are you sure it's not speed sensitive power steering? I had that on my 406 coupe. At slow speeds the steering was loose and easy to handle, at higher speeds, the steering stiffened big time

[peppernick]

Just spoken to Andy, the steering wheel locks when he boots it from a standstill and he can't turn the wheel past a certain point. At high speed cruise, the steering goes back to normal. I don;t think that's a feature of speed sensitive steering, sound to me like something might be binding. Furthermore, speed sensitive steering was not an option on E39s AFAIK.

The E39 M5 has the same steering set up and I haven't experienced what was described by Andy. Maybe Tin , Cable guy and Whizzkid can confirm.

Some info on recirculating ball steering (sound like a very complex set-up)



what's the difference between the 2 steering systems? is one more expensive to make than the other? is one considered superior? finally, what are the advantages and disadvantages of the 2 systems.
Thanks to everyone who helped answer this question.


Recirculating ball and nut steering gear consists of several parts contained in a steering gear housing. The steering gear shaft is connected to the steering wheel either directly or through some type of flexible joint. There is a worm gear on the end of the steering gear shaft. A cross Pitman shaft is mounted in the housing in a position 90 degrees to the worm gear. A ball nut rides on the worm gear and a gear on the cross Pitman shaft, called the cross shaft sector, is engaged with this nut.

Ball or roller bearings are used to support both ends of the worm gear and are adjustable to remove end or side play from the worm gear. The cross Pitman shaft is supported by bushings, needle bearings, or a combination of the two, and provision is made to control the worm and cross shaft clearance. All parts are enclosed in a cast housing that is partly filled with lubricant. Seals are used to prevent the entry of dirt or the loss of lubricant. Provision is made to bolt the steering gear housing to a rigid area, usually the frame.

The ball nut has internal threads that are meshed to the threads of the worm with continuous rows of ball bearings between the two. The ball bearings are recirculated through two outside loops, called ball guides.

The sliding ball nut has tapered teeth cut on one face that mate with teeth on the sector. As the steering wheel is rotated, the nut is moved up or down on the worm. Because teeth on the nut are meshed with the teeth on the sector, the movement of the nut causes the sector shaft to rotate and swing the steering linkage connected to it.

The recirculating ball construction results in a friction-free contact between the nut and the worm. When the steering wheel is turned to the left, the ball bearings roll between the worm and the nut and work their way upward in the worm groove. When the ball bearings reach the top of the nut, they enter two ball guides and are directed downward into the worm groove at a lower point. When the steering wheel is turned to the right, the ball bearings circulate in the opposite direction.


However ther are some inheant differences with Rack-and-pinion Steering Gear. Because the recirculating ball steering gear has the disadvantage that it occupies a good deal of space, usually in the engine compartment. The rack-and-pinion steering gear was first developed for compact cars in which the engine compartment space was limited. The rack-and-pinion system has worked so well that it is currently being used in both imported and American compacts and intermediate size cars.

The basic parts of a rack-and-pinion steering gear are shown below. The steering wheel and steering shaft are connected to a pinion gear. The pinion gear is in mesh with a straight bar that has gear teeth cut into one side. The toothed bar is called a rack. When the driver turns the steering wheel, the pinion gear turns, causing the rack to move. This movement, in turn, is connected to a linkage that moves the front wheels.

The rack-and-pinion gear is mounted in a rack housing assembly. The steering linkage consists of two inner tie rods and two tie rod ends. The inner tie rod ends are attached to the steering rack ends. The outer tie rod ends are attached to the suspension arms on the steering knuckles. Rubber boots are used to cover and protect the inner tie rod assemblies from road splash. An exploded view of the rack-and-pinion steering system is shown below.

In short many BMW e39 5 series owners perfer the 528i because it has rack and pinion steering whereas the heavier stablemate 540i uses recirculating ball construction. The driving impressions associated with the two are recirculating ball construction does not offer the percise and genine feel of rack an pinion at high speeds. Many performance oriented drivers would natuarally choose the 528i because of its better handeling characteristics thus the reason why Alpinas modified e39 5 series is based on the lighter more nimble 528i.

[All ON U]

I don't have that problem with my 540i.

[Shuriken]

I've heard of some BMs having variable power sterring depending on what you are doing but that doesn't sound right at all. Best get it checked mate.

Shuriken.

[cableguy]

Sounds like a Dealer fix to me.

Not sure about the e39 540i Sport, however on the e39 M5 when the Sport Button is pressed this systematically stiffens/weightens the steering response according to your speed. It is noticably heavier than standard but nothing like what you are describing with your car. [hmm

Here's hoping its an easy fix. ;)

C.