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View Full Version : what causes old cars to vibrate at high speeds?



Adamantium
22nd April 2004, 09:38
Having thought it over, I think I am happiest to hang on to the golf gti.

With this in mind I would like to cure one thing which annoys me about it, and that is the vibration I can feel at certain resonance speeds.

I have felt it before in older less solid cars, but didnt expect it from a vw.

I can only conclude it is down to age. Metros seem to do it regardless, but other golfs I have had have not suffered this.

I am wondering if people know the solution.

I am guessing that the only part which would specifically wear which could create this kind of thing are the bushings in the suspension and steering which may have perished or simply just worn out with age.

Wiould replacing the entire lot at the front with say powerflex bushes (cheaper than originals) be likely to stop the resonance?

dnb
22nd April 2004, 11:22
Alloys with flat spots in them from age and being bounced over potholes & kerbs for 10 to 15 years...

The wheel balancer can probably give the appearance of a properly balanced wheel, but it may not be round!! (My old Peugeot suffered from this, but I didn't understand anything about cars then - only that you had to change the oil & plugs.)

I agree that the bushes will be worn too.

Adamantium
22nd April 2004, 11:29
the car is a P reg with 120k on it.

it runs perfectly and I am otherwise very happy with it.

the rims appear also to be in excellent condition, and aren't low profiles (15s) that would be taking large knocks.

Good advice though.

I don't see the issue though with non round alloys, surely if the balance is there, they won't impart any vibration (unless you are going over bumps or round bends where the gyroscopic effect will make the other moments of inertia more prevalent).

This vibration occurs on straight flat motorways.

David_Wallis
22nd April 2004, 11:47
its the armco youve driven into whilst being asleep :D

Bushes..
TCA's
Lower Balljoints.
Suspension
Wheel Bearings.
Steering Rack.
Arbs

Check them for a start..

Dont put powerflex on, just OEM or aftermarket parts.

David

dnb
22nd April 2004, 11:51
I would have thought the same as you regarding the balance. But then I also thought that they are balanced at relatively low speeds and only to an accuracy of something like 5 grams.

I found a fairly major flat spot on the back of one rim on the Pug shortly before I sold it. I didn't have the wheel repaired, as it balanced up OK, and I knew I was selling it in the next week or two but I always wondered about it. I would hope that the tyres would have enough "tolerance" to take out any minor inaccuracies in wheels, but when does something like this start to be "major"?

Another thing that caused the Pug to shake on the motorway was that it would get one wheel in the ruts caused by HGVs in the left hand lane and the other wheel just not sitting in the other rut. (Hope this makes sense) The result was that the car would "bounce" in and out of the ruts. If you moved over into the middle lane, the problem reduced substantially.

For some reason, this isn't anywhere near as bad in the Scoob. Maybe because I drive faster and spend less time in the lane? Or maybe the Scoob suspension isn't quite as worn out, or the tyres/track etc are sufficiently wide to sit fully in the ruts.

Adamantium
22nd April 2004, 13:05
trouble is I dont know hwo effective these checks will be when the car isnt moving at speed.

Is it really giong to be noticable?

Floyd
24th April 2004, 19:47
That's the problem with problems like that on older cars. How much do you spend on them with diminishing returns?

Some cars are OK until they develop some annoying feature (clutch judder, brake judder, wheel vibrations or squeeky alternator belts). You start to fix it and somehow the problem never fully goes away. You put more and more money in to the car and new problems crop up or the old ones return.

In the end you get so pissed off that you sell it and wish you'd not spent so much on it.

Not a cheary thought but I think most have been through this scenario.

F

stevieturbo
24th April 2004, 20:09
Pretty much all cars I drive are quite old, and Ive never experienced any such vibrations ??

What sort of wheels are on the car, and more importantly do they have the spigot rings to locate them onto the hubs?

Ive seen cars fitted with alloys, where the wheel bore was larger than the hub spigot without spigot rings fitted, and it can give a very strange vibration through the car, yet nothing is felt through the steeering.

Adamantium
26th April 2004, 10:43
car is totally standard.

i wanted to keep it that way.

It was fleet car and I have receipts showing its proper maintenance regardless of cost.

Alloys are still standard and in good condition. I recently changed the tires and had all wheels properly balanced.

johnfelstead
26th April 2004, 19:12
but are they round? balancing doesnt tell you that.

Paul@Zen
26th April 2004, 19:29
what causes old cars to vibrate at high speeds?Pat's backside?

V-Bird
27th April 2004, 14:50
Adam, this is actually 'old car drone' it is a natural consequence of unitary construction, over time the panels attached to the monocoque develop sympathetic resonances, the way to negate the effects are to change the way in which the frequencies are propogated through out the car.

Not easy...

I think the best way is to 'paint' the underside of the car with bitumen type paint.

This at least changes a substantial part of the unitary and may just be enough, if not then it is the following in the this order..

Bonnet. [glued additional damping avoiding just a mat, singular locus points.]

Door. [same]

Roof. [same]

David_Wallis
27th April 2004, 14:57
so, in english, underseal has fallen off and you need a square of sound proofing on the bonnet, door (which one?) and the roof. :D

Cord
27th April 2004, 15:07
Ha ha ha PMSL nice one David,

Only mycroft could come up with all that bullsh1t instead of just saying "its an old car with wobbly bits, slap some gunk on it until it stops"

Adamantium
27th April 2004, 15:09
the vibrations is purely in the steering wheel, not in the body as such.

The pannels dont rattle at all and the dash doesn't vibrate.

It literally is like unbalanced wheels, but is only between 90 and 95mph (on my private estate), the rest of the time there is no noticable vibration in the steering.

The bodywork and interior trim is as solid as if it were brand new.

dnb
27th April 2004, 15:10
Fill all the gaps up with expanding foam?

Paul@Zen
27th April 2004, 15:12
unbalanced brake discs

when were they last replaced?

V-Bird
27th April 2004, 15:14
DW, thanx for providing an idiots translation, really appreciate that... :D

But sadly too simple, the underseal may be entirely intact and a square of sound proofing is not what I said, the idea is to change the frequency, not lessen its amplitude as eventually the intrinsic frequency will overcome this and the car return to its' noisey ways...

A simple pad will mean that instead of the panel vibrating at 120hz [the most irritating frequency] it instead will find another frequency, just as loud, just different... for the moment.

Frequncy damping [true] is about banding.

So if the Golf has a swage line in the door, then an additional strip along its' length is probably the best manner to effect this, it is important to take the damping right into the 'corners' of the door returns.

V-Bird
27th April 2004, 15:17
Originally posted by Pavlo:
unbalanced brake discs
How does that happen?

Paul@Zen
27th April 2004, 15:20
because the brake discs are balanced from the factory in the unworn state, with those small clip in weight things. After 1000's of miles of wear they may not be balanced as they were, in the same way that tyres can become unbalanced as they wear.

Paul

V-Bird
27th April 2004, 15:22
Originally posted by Adam M:
the vibrations is purely in the steering wheel, not in the body as such.

The pannels dont rattle at all and the dash doesn't vibrate.

It literally is like unbalanced wheels, but is only between 90 and 95mph (on my private estate), the rest of the time there is no noticable vibration in the steering.

The bodywork and interior trim is as solid as if it were brand new. This is quite often the manner in which whole body vibration will make itself apparent, the use of a colapsable steering column mean that the only outlet for the compound frequecy of the structure to be released.

Put an additional damper on the steering shaft [grip the wheel tight] and then the whole car is noisier, you have to deal with the compounded effect.

V-Bird
27th April 2004, 15:25
Originally posted by Pavlo:
because the brake discs are balanced from the factory in the unworn state, with those small clip in weight things. After 1000's of miles of wear they may not be balanced as they were, in the same way that tyres can become unbalanced as they wear.

Paul No, discs are balanced [occasionally] by machining, in use the rotational scrubbing actually improves their balance.

David_Wallis
27th April 2004, 15:27
Your welcome V-Bird.

PSML now.

David

Cord
27th April 2004, 15:29
Originally posted by V-Bird:
This is quite often the manner in which whole body vibration will make itself apparent,Ok that makes sense


the use of a colapsable steering column mean that the only outlet for the compound frequecy of the structure to be released.And a translation into english would be???

Paul@Zen
27th April 2004, 15:30
v-bird,

you are incorrect

Adamantium
27th April 2004, 15:35
v bird, I understand what you mean and will try the extra damper next time I find a suitable road on my estate.

You think that dynamat could be the solution to my problems.

Interesting.

Paul,

can you qualify your refutal of what Iain said please? It need not get into a slanging match, am hoping that can be put behind us and two clever people can have a reasoned discussion.

Paul@Zen
27th April 2004, 15:39
Adam,

I'm assuming your gti uses vented brake discs? They are not uniform in mass due to venting. Small metal wire clips are inserted from the inside to balance up the disc. If the venting isn't perfectly aligned and uniform within the disc, any wear will change the balance of the disc.

Paul

V-Bird
27th April 2004, 16:09
Originally posted by David_Wallis:
Your welcome V-Bird.

PSML now.

David It's good to laugh.

V-Bird
27th April 2004, 16:15
Originally posted by Cord:
</font><blockquote>quote:</font><hr /> the use of a colapsable steering column mean that the only outlet for the compound frequecy of the structure to be released.And a translation into english would be??? </font>[/QUOTE]On old cars you may find the ashtray or something will buzz it sits there annoying the life out of you, the reason is that the frequency was transmitted thru the surrounding materials and finally finds something that will move easily, easy movement means that the energy has a something to work on, the Ashtray may have been just right for either the frequency or the waveform that was imparted to it, in either case the energy was disippated this way, on some cars you stop the ashtray from vibrating and the door mirrors 'tingle' that is because the energy has not disippated without creating noise.

Now just substitute the ashtray for the steering column and perhaps you see what I mean?

[ 27. April 2004, 05:22 PM: Message edited by: V-Bird ]

V-Bird
27th April 2004, 16:21
Originally posted by Pavlo:
Adam,

I'm assuming your gti uses vented brake discs? They are not uniform in mass due to venting. Small metal wire clips are inserted from the inside to balance up the disc. If the venting isn't perfectly aligned and uniform within the disc, any wear will change the balance of the disc.

Paul I have never come across these 'add-ons'... I don't say they dont exist, just never seen them on any car I have either owned or worked on, I have seen the vents machined out and even the edge of the disc with the tell-tale crescent moon cut out...

I would like to see thes clips.

Cord
27th April 2004, 16:24
So it should have said "the use of a collapsable steering column mean[s] that [it is] the only outlet for the frequency of the compound structure to be released [from]" ?

Sorry just struggled with the english not the technical content.

V-Bird
27th April 2004, 16:29
Yep, I tend to have the answers in my head instantly and typing takes me ages, by the time I have re-iterated it in my head a hundred times it does tend to have some bits missing, a quick mind does not fit in well with any keyboard.

Cord
27th April 2004, 16:32
Try "right click" then copy and paste.

V-Bird
27th April 2004, 16:35
From where?

johnfelstead
27th April 2004, 17:34
Originally posted by V-Bird:

Now just substitute the ashtray for the steering column and perhaps you see what I mean? It's gonna handle like a bitch if you do that. :D

V-Bird
27th April 2004, 17:47
True, you'd have to lean over to the central console to steer, removing one buttock from the seat, thereby severely curtailing the messages from one of the biggest driver aids...

The irony is, real racers 'listen' with their ahse, bar-room racers talk thru it... :D

Adamantium
27th April 2004, 18:05
very interesting, so just to reiterate, which panels of the car first and how much sound deadening are we talking about?

will dynamat do?

from memory there isnt a lot of available space under the bonnet due to the existing insulation.

paul,

the front brakes are indeed vented disks. the rears may be too but I havent looked i a while.

gaving said that I think th brakes are fairly new.

surely if it were a balance issue would the problem be proportional to the road speed?

johnfelstead
27th April 2004, 18:23
Originally posted by V-Bird:
The irony is, real racers 'listen' with their ahse, bar-room racers talk thru it... :D PMSL i'll have to remember that one, classic truth. :D

johnfelstead
27th April 2004, 18:26
Adam, surely the easiest option is to either slow down or speed up, it's hardly a critical speed range. It's an old shed, dont throw your money away on yet another car. ;)

V-Bird
27th April 2004, 19:21
Originally posted by johnfelstead:
</font><blockquote>quote:</font><hr />Originally posted by V-Bird:
The irony is, real racers 'listen' with their ahse, bar-room racers talk thru it... :D PMSL i'll have to remember that one, classic truth. :D </font>[/QUOTE]Quote me any time you like, lots do.

David_Wallis
27th April 2004, 19:53
did you check for run out when the brakes were done adam?

David

V-Bird
27th April 2004, 20:03
Or more likely how about tyre eccentricity, I would put that quite far up the list...

[Firestones were once notorious for this 'attribute']

Jack the front up, get a dial measure, secure it firmly to the floor and on a continuous band around the tyre and measure the max/min...

Adamantium
28th April 2004, 12:09
again, why would that only appear at 90 then leave by 100?

Paul@Zen
28th April 2004, 12:29
because although the vibration source may be slight, if the frequency causes some panel to resonate it will be frequency and speed dependant.

dnb
28th April 2004, 12:50
I suppose you could buy a small hammer and go round and put little dents in every panel. This should alter the resonance characteristics enough... ;)

Adamantium
28th April 2004, 13:47
nope, got those already, they probably caused it.

I am having trouble accepting that compomund resonance of body panels could cause this degree of resonance in the steering column. Isn't it isolated from everything but the steering rack?

V-Bird
28th April 2004, 15:39
Originally posted by Adam M:
I am having trouble accepting that compomund resonance of body panels could cause this degree of resonance in the steering column. Isn't it isolated from everything but the steering rack? No, it is the other way round, the principle being that in an accident it separates from the front wheels at a knuckle down its' length, thereby stopping it from skewering you in your seat, it should also deform toward the centre console on pre-airbag models, with an air bage it will be catch-locked into position.

johnfelstead
28th April 2004, 16:14
Originally posted by V-Bird:
Quote me any time you like, lots do. ewwwwwwwww. http://instagiber.net/smiliesdotcom/contrib/ed/before.gif

johnfelstead
28th April 2004, 16:16
swap your wheels back to front and see if that changes it.

V-Bird
28th April 2004, 16:39
Originally posted by johnfelstead:
</font><blockquote>quote:</font><hr />Originally posted by V-Bird:
Quote me any time you like, lots do. ewwwwwwwww. http://instagiber.net/smiliesdotcom/contrib/ed/before.gif </font>[/QUOTE]If that's a thank-you then 'you're welcome' :D

Adamantium
28th April 2004, 17:20
I thought about swapping the wheels round. Will I not notice a different kind of vibration when it comes from the rear wheels.

johnfelstead
28th April 2004, 18:11
LOL @ VBird

Adam, do it, then you will be able to answer your question. ;)

micared
28th April 2004, 23:21
Sorry to interrupt, but it's just possible that having the wheels balanced on the car will solve this. This, if done properly, will eradicate any imbalance that a car of this age is likely to have accumulated in driveshafts, hubs, brake discs, etc. Also, if it works, a cheap fix, the best kind!! :D Hope this is of some use.

Adamantium
29th April 2004, 07:14
will do it this weekend if I get the chance.

micared, I had heard of this a long time ago but didn't know what whas involved and suspected it was bollocks.

Can you confirm what they do to do this?

How can they detect imbalance if the wheel is on the car still?

micared
29th April 2004, 09:41
Hi Adam, I used to work for ( whisper it ) Ford before I could stand it no more and left for the sunny horizons of Toyota. The Ford dealership had an on car wheel balancer which , basically, involved the offending wheel/wheels being jacked up, and the balancer, which was, in essence, a 2 foot square box, containing an electronically driven motor, with a seat for the operator , pushed up against the wheel to be balanced. The contact point on the balancer was also a wheel , and this was simply pushed up against the bottom of the tyre, at an angle of 90 degrees . This box of tricks had a digi. readout and was very effective at curing the more troublesome balance probs. I had first hand experience of this on one of my own cars, found it to be a solution to a problem not too dissimilar to your own. Hope you get sorted with it , stuff like that drives me mad. smile.gif

Adamantium
29th April 2004, 09:53
where can I find such a balancer, not having a ford and all!

micared
29th April 2004, 11:15
Iirc, the last time I had this done was at A.T.S, after I stopped working for Ford. However, can't see why you need to own a Ford to have your wheels balanced at one of their dealers. Just a matter of finding out who still provides this service, it was so effective I can't believe it won't exist anymore. To be fair, it's been a while since I've needed to know, but you shouldn't have too much difficulty, any decent tyre supplier should have heard of the process, if they can't do it , they should know someone who can.