Car is skipping laterally over bumps

[Alpinestars]

Can anyone help with a diagnosis please.

I've changed the DRC system on an RS6 to A Bilstein coilover set up and I think it was ok when it was fitted, but since a ride height change (lower) the rear and particularly the near side skips slightly sideways going over bumps like manhole covers.

We've checked the springs and dampers and all seems to be ok - they've only done about 1k in miles. I've reset the ride height to the original setting when things seemed to be ok.

What could cause these symptoms? Control arms, bushes, alignment etc?

Thanks.

[Matt Seabrook]

Sounds like a bump steer issue.

[Alpinestars]

Matt Seabrook said:

Sounds like a bump steer issue.

Thanks, I forgot to mention it's on the rear only.

[Locknut]

I think Mat is right. (note that he said "bump steer", not "bum steer").

Have your alterations effected the toe of the rear suspension?

If it is significantly toed in or out there would be a contest between the rear wheels, each pushing or pulling sideways against the other. A road defect such as a manhole cover could upset one wheel and cause a brief loss of grip. The other wheel would then have the upper hand briefly and move the car sideways. Such a fault will cause uneven tyre wear but you probably have not done enough mileage yet for it to show.

[andyiley]

Sounds more like the camber was not corrected when the lower ride height was set.

I have had the same and an e36 & e39 when doing this myself until corrected.

[Alpinestars]

Thanks for the response guys. One thing I've also noticed is that the offside is sitting slightly lower than the nearside despite the dampers both being set to the same height.

From what you've said, it sounds like an alignment is the first port of call. Would this impact ride height as well or is that something else?

[The Wookie]

Alpinestars said:

Thanks, I forgot to mention it's on the rear only.

Bump steer affects the rear too, particularly on multi link systems.

That said I can't imagine it's your issue unless you've absolutely slammed it.

[Alpinestars]

The Wookie said:

Bump steer affects the rear too, particularly on multi link systems.

That said I can't imagine it's your issue unless you've absolutely slammed it.

Thanks.

It looks like it was a geo issue as it seems to have been sorted. Thanks for all the replies.