Vib b b b b b ration

[peteyg]

Right chaps, need some input here as to what the cause of my vibration might be. The old girl has been off the road for 2 months due to some cosmetic needs so I decided to attack the steering system to try and solve this nasty vibration I've got.

Symptoms - a constant brrrr brrrrr brrrrr vibration coming through the steering wheel, more noticable at 40mph + but doesn't increase with speed/revs. The vibration can also be felt thoughout the car - I mean the whole thing vibrates (like a giant sex toy if only I was female...). It's not transmission based as the vibration is still there with the clutch pedal down or when coasting in neutral which is a relief.

What I've done so far - new steering rack, new steering u/js, new tyres, balanced wheels, tracking set, replaced driveshaft u/js.

Suspension bushes front/rear? There's no obvious play...I'm stuck!

Arrrgghhh!!

All ideas welcomed. It's still great to be driving again though despite the mild irritation.

Pete

[bigsi]

you checked the discs are not warped?, bearings, also get a 4 wheel laser alignment.

thats all i can think of at the moment.

[Paul C]

but doesn't increase with speed/revs.

Thats a real puzzler!

Just about all the things i can think of would increase with speed or revs, eg:

Warped discs, bad wheel balancing, flat spots from braking etc etc.

How are the engine mounts?

[Advantage]

It might be worth checking the engine and gearbox mounts, perhaps either the transmission or engine is touching the chassis somewhere?

[Goose]

I had major vibrations too - it turned out to be the wheels - a flat spot had developed where the PO had left it standing for months.

[andydclements]

Persistant vibration- that ring a bell with my s3.

THINGS TO KEEP IN MIND.

the source and the area you can notice it don't have to be the same or that closely related.

Just because it doen't get worse with speed doesn't mean it's not rotating part related.

Just because you've replaced a part doesn't mean it can be eliminated.

My wobble upon braking has been changed, I replaced many bits, but the most effective was changing wheel bearings for a second time , then found the 1st replacement set had been machined with minor issues, meaning the brake disc was hitting the hub carrier.

Mine has now gone from wobble on the wheel to nasty fore-aft vibration while braking. I'm replacing the lower wish bone inner bushes with nylon as the guy who pressed them in with 10 / 20 tonnes had trouble getting the original type ones in, so had to be re-spaced.

To give everybody a good bit to go on, please describe the symptoms and scenario more, along with any history.

Vib on wheel, fore- aft , judder , rotation of steering wheel etc.

you say at 40mph, does it only start at 40, does it fade in, what happens if you drop below 40 ?

new tyres, front, back, all?

Wheels balanced all round?

What if you coast in neutral with the engine off?

Does applying the brakes gently alter it at all?

Does applying the hand brake alter it at all?

Bits replaced recently?

Did this issue grow/ suddenly occur?

Load we can ask, please let us know anything that might have happened.

Andy

[WayneB]

Like a few of the others, Im thinking engine/transmission mounts (worn out or broken) allowing the engine /trans to be misalligned and or driveshaft UJs (were they replaced with quality parts? ie not from ROC) Or they were incorrectly installed (not centred properly or damaged)?

What Andy said about crap offshore wheel bearings is totally valid also.

[Artie]

Like a few of the others, Im thinking engine/transmission mounts (worn out or broken) allowing the engine /trans to be misalligned and or driveshaft UJs (were they replaced with quality parts? ie not from ROC) Or they were incorrectly installed (not centred properly or damaged)?

What Andy said about crap offshore wheel bearings is totally valid also.

I had the same problem on my C32 AMG mercedes, turned out to be a bent wheel. Got new tires, balanced and everything, when I took the wheels off to have them refurbed for curb rash, the guy doing the work put them on the runout machine and turned out 2 of my wheels were slightly bent from potholes! Worth a check.

Artie

[Esprit Aviation]

Had a BMW in the shop recently that had steering wheel shake @ certain speed. I noticed all 4 wheels/ tire combos out of round w/ variation form side to side of each tire. Several other shops rotated, balanced, etc, etc, many times w/ no effect. I chose the worst one on the front, put on the narrow,apparently unbalanced, spare and the problem almost completetly went away. It pays to try something drastic.

Since all 4 were out of round the prob would never go away.

First, you cannot make a tire run true by balancing. Second, the other shops must not have turned them slowly on the balancing machine to notice the out-of-round condition. Third, it is possible that the car went over a curb head on, and it bent all 4 rims. Fourth, even though the outside of the rim appeared (and probably was) unbent, the inner part of the rim that is not supported by the 'spokes' of the wheel was bent. This caused the vibration, and would not be readily seen. I suppose most tire shops asume that if the outer edge runs true the inner must run true as well. Not so!!

Long story short, stick a spare on and see what happens! If the characteristic changes, it is likely that the prob is w/ the wheel you removed.

Let us know.

Cheers, Lee

[peteyg]

Thanks for the input guys!

Story so far. Went for a long drive today and noticed that the vibration starts at 50mph and gets more severe the faster I go but the rythmn remains constant.

anyway started taking off the wheels to get them balanced (don't trust the monkeys at the tyre shop to do it) and noticed there is a tiny amount of vertical play in the right hand front hub. The castle nut was not even finger tight. Doing it up finger tight with an extra fraction of a turn with a spanner so that the holes for the split pin line up and the play was gone but then there was some friction of disc on pad. Question is without the tools to check for correct end float, will I be doing much damage if I put it back togather and go for a blast to see if that solves it? I assume that the pads will adjust to the new rotation angle of the disc? It makes it very clear in the book that the bearing mustn't be over stressed by thightening the nut too much. Left hand side is solid with the nut done up tightly but hub rotating freely...

What do I do?

[peteyg]

Right...couldn't be bothered to wait for an answer so tightened up the hub nut to the next notch put the wheels back on and went for a blast up the A3. Interestingly the symptoms have been aleviated, not gone but better. What's the chance of having deformed the bearing or knacked some other part of the hub by driving with a stightly loose nut?

P

[USAndretti42]

Peter,

When did you last re-pack your front wheel bearings with grease? It's supposed to be done regularly. Can't remember how often right now, but I think it's fairly frequently. Is there any play at the wheel? Can you rock the top and bottom? How does the left compare to the right?

[peteyg]

Hi Trevor,

The bearing was greased last August when I put new discs on the front. Now there's no play after tightening the nut to the next notch. No play on the other hub either.

Do you think it's worth replacing the bearing anyway?

Pete

[andydclements]

Hi Trevor,

The bearing was greased last August when I put new discs on the front. Now there's no play after tightening the nut to the next notch. No play on the other hub either.

Do you think it's worth replacing the bearing anyway?

Pete

I think for the proce of 4 bearings go for it, if one side has gone, what's the chance the other side don't have too long left?

If the bearing is runwith the incorrect torque , in this case too little, it can put un-eaven pressure on teh faces and cause them to start to deteriorate quickly.

The pig of the job is setting the end float.

Andy

[peteyg]

Think you're right Andy. I'll swap bearings. What I don't get is how you adust endfloat for such a tiny gap when the nut will only allow huge increments so the holes for the split pin line up?

Pete

[tonyp]

Castellated nuts ? (Your knuts m'Lord) ?

[peteyg]

Castellated nuts ? (Your knuts m'Lord) ?

Plain, salted or dry roasted?

[andydclements]

Don't forget the holes through the nuts & pin usually allow 1/12 of a turn adjustment ( 1 flat or half a flat adjustment), so on a 1.5mm pitch (i think it's circa 1.5mm from peak of thread to the next peak) that's approx 0.12mm.