E39 M5 Elusive Vibration...

[derestrictor]

Dear //M People,

The old girl now has one, troublesome issue.

Bearing in mind that this week saw new drop links, control arm bushes, comprehensive suspension appraisal (yielding clean bill prognosis), all new tyres and the alloys 100% ito there being no imperfections and balanced up, the continuing, unwelcome prescence of the 70-80mph shimmy has us all quite bemused.

The poise of the car in general is fabulous, the suspension feeling 'refreshed' and below and above this range, it is the model of stability I always knew the thing to be.

And yet, in 90% of 70-80 cruise scenarios, there is a most definite tremor through the wheel, felt too through the seats. The chief tech is nearing full bemusement and is investigating further this coming week.

Is there anything from the category labelled 'bleedin' obvious' that needs ticking?

[jeremyc]

Propshaft balance? Engine mounts? Steering rack wear?

[jeremyc]

Excess of wax on the paintwork?

[derestrictor]

I think I've suggested these but I'll mention them again, fanx.

[belleair302]

Check everything related to the anti roll bars and or thrust arm bushes.

[Egbert Nobacon]

Rear carrier mounts ? - Need a special tool to remove - even some main agents don't have it.

Has your dealer tried a different set of wheels - any e39 compatable set will do (as long as they clear the discs) and see if it occcurs with them on a test drive.

A bit tricky, but can you run it on a ramp at the speed/revs that the vibration occurs. If it occurs with the rear wheels off the ground its less likely to be suspension and more likely drivetrain,

TBH I had this on one of my E39's and went through all you have both with BMW main agent and later a Specialist - couldn't get rid of it so I chopped it in.

Edited by Egbert Nobacon on Friday 22 February 08:28

[gavm5]

Run out of wheels or tyres, or maybe a flat spot on the tyres ?
Once in the 70-80 zone if one of the above present then the shimmy 'may' be in tune with the speed.

[mondeoman]

Smacks of wheels beinbg out of balance at that speed.

Doesn't take much to do it.

HTH

[derestrictor]

Cheers guys but what about this, maybe?

http://www.ca-automotive.co.uk/products-Y2FyX21ha2...

I just have this inner feeling it's a frequency/resonance somehow connecting transmission and chassis...

[belleair302]

Have a look at the existing mounts and decide if they need replacing before buying Rogue kit. I am not convinced that these will be of any benefit.

[derestrictor]

Will do, Boss.

Frankly, I will literally pull the fecker apart until it's perfect. I've spunked so much on this baby already, terms like value or 'worth' are irrelevances, I just want it spot on.

[belleair302]

Who is your preferred garage or specialist re the BM?

[Murdock]

derestrictor said:

I just want it spot on.

You sound like my dad after buying his M5. Three trips back to the dealer for various issues (steering alignment being the most prominent one) and the car still isn't to his satisfaction. At least the steering wheel is straight now as opposed to at the one o'clock position, with claims that "they all do that" and "it's as straight as we can get it" seemingly long forgotten. As for the tremor you are experiencing, it could potentially be what you found in that link, but don't rule out the new tyres (how has she been shod, incidentally?).

Edited by Murdock on Friday 22 February 02:54

[Yung Man]

Would there be any chance of putting the new wheels and tyres on another car and running that one at 70-80mph just to eliminate them from the equation?.

[ASBO]

Der,

I am experiencing a similar vibration at ~60mph in the old girl which I have been told is the prop-shaft 'doughnut' after the wheels were balanced etc.

Whilst this may sound obvious (and I'm assuming this avenue has already been trecked), this little blighter can oft' be overlooked.

Thrust arm bushes and the like are unlikely to cuase you the same vibration unless you are braking or coming orf the throttle IME.

My guess is that it's tranny related. This is an issue that seems to affect all bimmers as they adavance in years and is especially prevelant on the E36, where most of the time the culprit is the aforementioned wee blighter.

[derestrictor]

Chaps, I don't know why but yes, the propshaft cum mounts side of things feels like a distinct poss: it's the way it 'comes on' under certain loadings: it's most prevelant in the 70-80 zone but it can be felt to a lesser degree elsewhere and often during a charge, it just feels like something's out of kilter, out of synch - and a rotating shaft which isn't quite true of axisional perfection I can imagine emanating the distortive frequencies which would resonate accordingly.

Oddly, it always feels worse when cold although M5 'breathing' generally is a documented issue so I spend a fair while warming her juices (ahem) and eventually trickling along very genteel like until temps are nicely up.

Unfortunately, the specialists are all southerly and I'm stuck with main agents and (hopefully ) salvation via what you guys are suggesting.

Re the wheels - I dunno but I just don't think it is them. Current rubber is nearly new Dunlop Sports but believe me, I tried all the others, it makes no odds and the dealer's chief tech bod assures me the wheels are 100%.

I'm going to mention all the 'arm' related possibilities but I suspect these have been checked over.

So annoying because 95% of the time it's fine (well, more than fine) and the whole way the heel n' toe/blip for sheer effect repertoire flows so naturally makes every journey utterly beguiling.

Don't worry I have some more tablets due at 11...

[Egbert Nobacon]

Just a thought Der.

Have all the discs (especially the rear) been checked for a flush fit against the hub. Any bit of crud/corrosion sandwiched in there could cause an imbalance. Even applies to the wheels.

Other solutions suggested to me when investigating mine where:

Have the wheels balanced ON the car (Apparently Hunter make a machine that can do this)

Check the location of the locking wheel nuts in relation to the valve.

Both the latter are longshots really but maybe worth trying as a last resort

[belleair302]

Have a look at the doughnut coupling at the front of the propshaft. It may well need replacing. Who is looking after your car up north?

Edited by belleair302 on Friday 22 February 11:31

[derestrictor]

Egbert, Belleair, thanks: the propshaft doughnut and/or the tranny mounts are currently even favourites.

The old dear is in again on Monday. We'll get there.

[belleair302]

That E34 would have been a much better acqusition than spending cash on an E39....you cannot beat a handmade, low volume limited edition car.