Wheels “echoing” through steering

[miketheman2k]

Apologies for the slightly odd title but it is a curious issue. I have a 2006 Audi RS4. When cornering reasonably quickly (nothing crazy) and the front wheels travel over uneven tarmac (e.g. bad surface, a drain cover, an undulation) there is the initial transmission through the wheels and the steering rack to the steering wheel but then it continues for a few more cycles than it should. The best way I can describe it is like when I used to fit massive heavy alloy wheels to a car that was never intended to deal with that unsprung weight, the result being an echo or reverberation of what the wheel was dealing with.

To help pin point the issue I have a list of things I’ve already refreshed and tried:
Upper control arms
Lower control arms
Trackrod ends
Wheel bearings
Springs & dampers
ARB droplinks
4 wheels alignment
Checked tyre pressures
Tightened steering rack slack bolt

Things I haven’t checked:
Driveshafts
Steering rack universal joint(s)
Power steering fluid (level is full, haven’t refreshed it)

I think I can rule out balancing/warped wheels/brakes etc since the steering doesn’t wobble in a straight line or under braking.

If anyone has any ideas what could be causing this frustrating issue on an otherwise brilliant car I’d appreciate it.

[miketheman2k]

Good question to which I don’t know have any other experience since I’ve only driven mine. Anecdotally I’ve never heard or read anyone talk about this issue so I’d say it’s not. It’s on standard wheels incidentally.

[miketheman2k]

E-bmw said:

I am thinking a combination of run-flat, poor quality/badly worn & under-profiled tyres would be my guess.

They’re OEM-sized Michelin PS4S’ so although not the brand from new, almost certainly better. I’ve used those and the Supersport predecessor on loads of similar cars and it’s always improved things, I’d be surprised if this was the reason.

[miketheman2k]

Smint said:

Isn't this how cars sitting on tyres with small aspect ratios with stiff springs and hard dampers behave over rough roads normally, skipping over bumps instead of following the contours.

No i haven't driven the car in question, just you only have to slip a set of smaller wheels with larger aspect tyres (typically a second winter set) on in place of the harder larger rimmed smaller aspect tyres to note the massive increase in pliability over rough surfaces.

Other thoughts, are the wheels OE, ie correct offsets etc, with correct OE tyre sizes and load ratings, also when you've checked pressures are you going by hight speed full load pressures, is there a lower pressure setting for normal driving lightly loaded?

Edited by Smint on Monday 7th June 17:53

This isn’t an issue with skipping down an uneven road, the B7 RS4 is actually quite softly sprung. The issue is purely felt through the wheel not the rest of the car. Additionally the contemporary reviews for that car were glowing about how compliant the ride was so I definitely think I have an issue rather than being the default.

The car did this when all the components were standard, so it isn’t a modification I’ve made that has created it or exacerbated it.

Does anyone have a B6/B7 Audi A4/S4/RS4 that could confirm they don’t know what I’m going on about? 😂

[miketheman2k]

Thanks for the help so far. The shocks have been replaced so this is unlikely to be the cause.

[miketheman2k]

rustednut said:

Is the issue, feedback through the steering wheel, or more kickback ?

If you hold the steering wheel turned at an angle when stationary, about to turn left/right, and hold the steering wheel in that position can you feel the steering wheel "pulse or try to move" or is it only felt when moving?

When stationary it feels completely normal as far as I can tell. Even when moving it is only harsh forces, like those acting on the sidewall that send a echoing “shimmy” through the steering wheel. Like the damping between the wheel and steering wheel isn’t what it should be (that’s the description anyway).

[miketheman2k]

Smint said:

Fair enough, so long as you're happy with the damping rates i'd be checking the steering column UJ(s) next, some cars have a tendency for the UJ just above the steering comun to start seizing, as you can imagine this would give a very disconcerting 'notchy' feel to the steering, sort of 4 sided threepenny bit effect if that isn't a contradition.

I’ll try and check the UJ’s. Afaik they’re not replaceable without a whole new steering column on the A4. Looking at the parts diagram there appear to be a bolt near it but I’m guessing that wouldn’t take slack out of the actual UJ?