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[alank46]

I have a problem.  At between 20mph and 40mph the car oscillates from side to side, it feels like an oval wheel or a bent wheel, but I've checked all the wheels/tyres and they are round and true.  It feels just as though somebody is rocking the car from side to side, its a gentle rocking, not harsh, but of quite large magnitude.  I can feel it mildly through the steering wheel but mainly it rocks me sitting in my seat.  Above 40 it disappears, braking is fine with no pulling or vibration and the symptom gets less the longer the journey.  I've had the car up in the air and can feel no looseness in any of the wheels or suspension components, tyres are round and true with no bulges, rear tyres are fairly new and wearing flat, the fronts are near the end of their life but still well legal although they are slightly more worn on both edges than the middle, but not excessively so.
Its got me beat, any suggestions as to what I've missed?

[Andy B]

out of balance rear wheels?  though I'd expect that to be more like a vibration through the car 

[feeutfo]

Is the wobble in time with wheel speed? Ie does it increase frequency in time with revolutions of the wheels ?


Is the wobble always present at that speed range without fail? Or sometimes does it at that speed sometimes not?

[alank46]

Yes, the wobble is in time with wheel speed.  It isn't always there, perhaps 80% of the time between 20 and 40, and getting more as time goes by. 

[feeutfo]

Ok, slightly conflicting answers, but it sounds like failed wishbone bushes are most likely. Specifically the front bushes, but could be both.

In severe cases where there is free play they allow the wishbone/control arm to flap. Like a tank slapper on a bike. Feels gyroscopic and the front of the car wobbles with the steering wheel.

A quick sharp jab on the brakes can set it off almost instantly, or a bump on one side of the road that only hits one wheel, are most reliable tests to set it off but it can occur at any time. ...and at any speed btw, but lower speeds seem more common.

Some tests to confirm, put a foot on top of the wheel and push it for and aft, if the wheel moves easily with more than say 5 mill of play, knackered bushes.

Or, jack it up at the front, both sides on stands, get under there with a bar and a torch and lever the wishbones in the gap between the wishbone end and the subframe.
There should be play, but need a great deal of force to move them. If they slop about, as sounds likely, buggered bushes.

A valid mot, does not mean the bushes are sound.


If by some odd chance the rear bush is ok via a visual check writhe wheel off then a cheaper and easier option could be to fit poly, available for the front only.

Hth.

[ffcgary1]

Could also be weak shocks, does it make you feel a bit seasick?

[alank46]

Chris
Thanks for that info, I will look at that and report back, as I haven't found anything else wrong I think you may well be right.

Gary
Ride is well controlled at speed so do not think its shocks, but worth checking all the same.

[car5car]

idler arm?

[feeutfo]

Ime when shocks fail, they loose damping, which means they bounce off the road at the slightest provocation. The slightest bump, or even out of balance wheel can start the wheel pogoing on the inside unloaded side of the car if its in a corner.

Not sure that fits the symptoms in this case tbh.

[ffcgary1]

When they start to fail, through experiance, it will feel like your driving on a sponge and make you feel quite unwell, but i know what your saying but normally they have to be very bad to do that.

[alank46]

I've had the car up in the air and checked the rear bushes on the front wishbone with my pry bar.  There is a fair bit of play, but I'm not sure how much is too much, and the rubber looks sound.  Anyway I filled the voids in the bushes with polyurathane sealant/adhesive as much as possible without dismantling anything and then tried the car.  Its 90% better so it looks like it is the bushes causing the problem.  Where do I get poly bushes from, the other bush and the ball joint seem okay so I do not really want to change the whole arm.
Also thank you to all those who offered solutions to my problem.

[ffcgary1]

Being that they are rubber will mean that there is some movement, but they should not be flopy, you should need to use a little bit of force to move good bushes, try super pro or even ebay omega poly bushes and you will find some there, now i am off to poly my jeeps upper and loewer axl arms, oh the joy of it all is just too much to cope with.
Ps it is nearly always the front bush that needs poly bushing.
Gary.

[feeutfo]

Poly for the front wishbone bush are made by powerflex. But you need to buy them from one of thier dealers. these can be fitted with the wishbone still on the car,
Provided means are available to cut or burn out the old rubber bush, thin jigsaw through the outer bush Collar. It's then a 5min job to fit the poly and bolt it back up.

There is no poly solution for the rearward wb bush, that we know of. If that's failed the arm needs to come off. But you sound like your in luck.

[alank46]

I'm getting too old for all this working on cars.  It is of course the FRONT horizontal bushes that I have checked and found have play, not the rears.  Bit of a senior moment there, I'm off to have a lay down now.

[feeutfo]

I'm getting too old for all this working on cars.  It is of course the FRONT horizontal bushes that I have checked and found have play, not the rears.  Bit of a senior moment there, I'm off to have a lay down now.

if your up this way....

....otherwise, dont let a garage charge you more than an hour. TOPS!