Ride feels a little busy/choppy

[Johnmed]

As above. First noticed this when I bought the car, feels like the wheels are slightly buckled or out of balanced. The day I bought it I had two new front tyres put on. They balanced fine. The rears I had checked more recently, and they took 60-75 grams per wheel to balance up properly.

On the motorway the car sort of vibrates a bit, like it's overdamped.

Before I bought the car, 4-5 weeks ago, I scanned it with VCDS, and I've done this again more recently, no faults were shown regarding the suspension.

In VCDS I ran the checks and the compressor had nearly 12 bars of pressure and each corner went up and down etc. The suspension otherwise operates exactly as it should, no warning lights, lifts and lowers, nothing is greyed out on the MMI, no knocks or clunks.

The other week I pumped the tyres up to high 30s and the ride was intolerable. I've since lowered pressures to 30/31 and this has helped a bit.

I'm a bit confused, the tyres are big balloon 55 profiles and I'd imagine the ride would be too soft if anything....

[Lee S]

Quality/Brand of tyres ?? Done a 4 wheel alignment check ??

[Johnmed]

Pirellis all round, correct fitment, speed rating etc etc. Had the tracking done when I had the fronts installed, (the fronts were worn on the outside edges, as noted on the MOT as an advisory) and the garage told me it was spot on, and didn't need doing.

I know the new tyres should theoretically go on the back and all four should be replaced at once, however, the rears are like new. I couldn't justify binning them.

Is a 4 wheel alignment necessary?

[Architex_mA8tey]

Sounds like a wheel may be buckled, especially if some are taking that much in weights, but could also be a steering or anti roll bar bush worn or even wheel bearing(s) on the way out do you have any noises? A recent one on one of our D3s turned out to be a combination of one buckled wheel (on the rear where it wasn't visible) and a groaning rear wheel bearing combined so we changed the wheel and the pair of bearings and now all is quiet and lovely

[Johnmed]

Cheers Lee and Architex.

I have no rumble or noise whatsoever. So I'm inclined to think it's the wheels or the rear tyres.... Just don't want to start replacing things needlessly.

[snapdragon]

If you think the wheels are buckled, you could ask a tyre shop to take them off and spin them up to check. I would really consider all the suspension arms and bushes too.

[Johnmed]

Cheers. When I had the rears balanced I payed special attention to the wheels when spun. One appeared slightly eccentric. The most experienced guy there said that wouldn't be felt in the car.

The car has extensive full dealer history. You'd like to think bushes would flag up?

[snapdragon]

The front arms' rubber bushes go, but you can usually see cracks with a torch if you turn the steering each way and look at the rubber bushes.
You also have 2 front antirollbar links and the antirollbar itself (with built-in inner bushes).

The rear axle has adjustable track but the rod bushes don't usually fail.

Air suspension cis more fidgety that steel due to the internal friction of the rubber air springs but those used in the A8 are quite a good design in this respect.

[Johnmed]

Think I may have my mechanic friend give it the once over. Or failing that, have an Indie take a look.

[Johnmed]

Ok, to update:

Had my mechanic mate drive the car and check over the suspension. The front wheels had new Pirellis on, and the vibration could be felt through the seat, so from the rear. The rear wheels had old Pirellis on. Mate swapped the wheels over, (front to back) and the vibration lessened AND was felt through the steering wheel and the car pulled to the left.

Mate noticed some odd wear on the old rear tyres. Hard to explain, but if you imagine viewing the tyre from above (like you're riding a bike) the surface area of the tyre that contacts the ground, was not entirely flat. One section say a cm across, slightly off centre and running around the tyre was not horizontal, but a few degrees off horizontal. Also one part of this section had a lip, like you'd tied an imaginary elastic band around the tyre....

Anyway, I had some new Pirelli P7s put on (to match the fronts) and the vibration/sensation has gone. Car now drives as smoothly as it ought to.

I'm thinking a 4 wheel alignment may now be in order, including rear camber alignment, is that possible on the D3?

Thanks in advance. John.