Possible tracking related vibration or not?

[jackwall5]

Hi folks,

[One of these days, I learn enough from here to both stop asking too many questions and perhaps help other with theirs]

CAR: W203 C220 CDI [2000] left hand drive.

This has just started to happen. As ever, some excellent reading here which has been very helpful.

Driving straight, no vibrations. All is well.

At slow speed not surprisingly, nothing untoward.

1) When at about 80 mph and only when turning to the left to follow the road I get a vibration coming through the steering. The vibration comes just as I turn off center. Straighten up and vibration goes away.

2) When I brake in a straight line from speed I get a serious vibration through the steering when I scrub the speed quickly. Take my foot off the brake and vibration does away.

Both the above sound like they're coming from the front right hand side wheel ..... if when inside a car, it's possible to pin point any noise.

My thinking at the mo is ....

1) worn bushing / play in the control arm on that side or tracking. [Car is older and I've never had the tracking checked since the car was new to me]

2) sounds like disk warp but this would not explain 1) to me. [Again car is old so disk may well need changing]

Of course, I could have both problems.

Other info of note.

* Right Rear spring is broken [at the 3 inch point at the bottom ....
* BAS warning light as come on a couple of times in the last couple of weeks but the malfunction clears itself when I turn off the ignition and restart the car.

Reading the forum here has offered lots of great info though 1) above was not really mentioned, hence my thread.

I looking for a bit a confidence about my thinking before I roll up my sleeves. Many thanks all.

Safe Driving

 

[djb]

Hi folks,

[One of these days, I learn enough from here to both stop asking too many questions and perhaps help other with theirs]

CAR: W203 C220 CDI [2000] left hand drive.

This has just started to happen. As ever, some excellent reading here which has been very helpful.

Driving straight, no vibrations. All is well.

At slow speed not surprisingly, nothing untoward.

1) When at about 80 mph and only when turning to the left to follow the road I get a vibration coming through the steering. The vibration comes just as I turn off center. Straighten up and vibration goes away.

would this occur if the wheel bearing has sufficient slack for the defective disc in 2 to lean on the pads?

2) When I brake in a straight line from speed I get a serious vibration through the steering when I scrub the speed quickly. Take my foot off the brake and vibration does away.

Both the above sound like they're coming from the front right hand side wheel ..... if when inside a car, it's possible to pin point any noise.

My thinking at the mo is ....

1) worn bushing / play in the control arm on that side or tracking. [Car is older and I've never had the tracking checked since the car was new to me]

2) sounds like disk warp but this would not explain 1) to me. [Again car is old so disk may well need changing]

Of course, I could have both problems.

Other info of note.

* Right Rear spring is broken [at the 3 inch point at the bottom ....


* BAS warning light as come on a couple of times in the last couple of weeks but the malfunction clears itself when I turn off the ignition and restart the car.

ABS lights come on with wheel bearing slack, others will comment on BAS & the same

Reading the forum here has offered lots of great info though 1) above was not really mentioned, hence my thread.

I looking for a bit a confidence about my thinking before I roll up my sleeves. Many thanks all.

Safe Driving

Sounds as if new discs & pads & o/s wheel bearing or adjustment are required.

 

[television]

90% of your problems are a warped front disc, since you only ever replace in pairs, it does not matter which one.

These have to be changed, and I would take it from there

 

[Number_Cruncher]

I tend to think that djb is on the right track.

 

[turbopete]

as above from me too. change the front discs and pads, adjust the wheelbearing and take it from there

 

[roofless]

i would check for worn thrust arm bushes too

 

[The Rock]

Rightly or wrongly I'd start with bushes. I don't know which one so I'd seek help from a technician by way of a road test.

As you say, I can't see warped discs causing [1]

Rock

 

[television]

Rightly or wrongly I'd start with bushes. I don't know which one so I'd seek help from a technician by way of a road test.

As you say, I can't see warped discs causing [1]

Rock

A bush or bearing cannot in its own right cause a wheel to shake, the brake disk has to be out of true or the tyre out of balance to start it off in the first place. a worn bush or bearing will allow it to shake more, but cannot start it off in the first place

 

[Number_Cruncher]

>>but cannot start it off in the first place

Sorry for being pedantic, but, actually, it can. The mechanism which allows this is the groscopic behaviour of the spinning wheel, where an angular velocity in one non-spinning axis result in a torque about the orthogonal non-spinning axis, which results in an angular motion, etc, etc, etc.

If the wheel were not spinning, I would agree that slack in the suspension couldn't start a vibration.

 

[television]

>>but cannot start it off in the first place

Sorry for being pedantic, but, actually, it can. The mechanism which allows this is the groscopic behaviour of the spinning wheel, where an angular velocity in one non-spinning axis result in a torque about the orthogonal non-spinning axis, which results in an angular motion, etc, etc, etc.

If the wheel were not spinning, I would agree that slack in the suspension couldn't start a vibration.

Sorry you are not right, a gyroscope perfectly balanced will run in any axis. A subject that I was taught much about when balancing flywheels and crankshafts.

 

[Number_Cruncher]

Malcolm, I'm not talking about unbalanced wheels, it's nothing to do with that.

I'm talking about what happens when you disturb a gyroscope suddenly - you get a reaction in the other axis, which, if there's freedom to move, can form a feedback mechanism, and the vibration can continue.

So, nothing to do with unbalance, this vibration mechanism can happen when the principal axes of inertia are perfectly aligned with the rotation axis.

 

[television]

Malcolm, I'm not talking about unbalanced wheels, it's nothing to do with that.

I'm talking about what happens when you disturb a gyroscope suddenly - you get a reaction in the other axis, which, if there's freedom to move, can form a feedback mechanism, and the vibration can continue.

So, nothing to do with unbalance, this vibration mechanism can happen when the principal axes of inertia are perfectly aligned with the rotation axis.

I know that we are not talking about wheels, it was an example of the thousands of post that we have on this subject, in this case it is the disc out, as bumping can be felt through the pedal and car, and a bearing cannot do that

 

[geoffreyw]

1) Move to England
2) Do not travel over 70mph
3) Always turn right, you will get home eventually

Sorry having a silly moment

 

[television]

1) Move to England
2) Do not travel over 70mph
3) Always turn right, you will get home eventually

Sorry having a silly moment

Not at all,a good cheap fix

 

[Number_Cruncher]

Here's the point you made earlier.

>>A bush or bearing cannot in its own right cause a wheel to shake,

I disagree with it, and, I've talked about the physical mechanism which allows slop in a suspension, aided and abetted by gyroscopic coupling from the rotating wheel to allow a vibration to occur.

Can you point to some physics, or theory, or published data which supports your view?

 

[television]

I stand by what I said, this fits in with the thousands of post on this subject, had the OP posted just saying that he had vibration when he braked, it would have all come down to the warped out of true disc, one of the most common post on the forum

If you want to make it sound much more complicated than it is, that is your privilege

I am proud of my engineering days of when I used to cast my own bearings and did my own line boring, and the balancing of all components

 

[jackwall5]

Hi all,

firstly, many thanks for the replies here.

geoffreyw .... :lol: it's one option for sure!

Symptom 1) above was the only reason I opened this thread. Otherwise, other threads already cover this general topic well.

Hoping not to sound like a fence sitter here, I can see valuable argument in the two main points of focus.

As djb first suggested, later reinforced by others and then added to by myself with the extra work items, I plan to ....

1) Give all corners of this car a good eyeball.
2) Change both front and rear discs and pads [if padwear is near/past 50%]
This is likely needed anyway and won't break my bank and I think it's a sensible investment
3) Possibly change the wheel bearing if it seems necessary.
4) Retest and see if issue resolved
5) Do all bushes and bearing in the torsion and control arms include any replacements deemed necessary
6) Sort out the rear springs


It'll be a few weeks before I'll get the opportunity to do this but I commit to report back when I resolve it.

Many thanks

Safe Driving

 

[Number_Cruncher]

I am proud of my engineering days of when I used to cast my own bearings and did my own line boring, and the balancing of all components

Which is fair enough and extremely laudable, but, alas, not relevant to this discussion.

If you want to make it sound much more complicated than it is, that is your privilege

I'm actually simplifying rather than complicating, I haven't discussed parametric excitation, or the mechanism for energy to drive the oscillation.

I stand by what I said, this fits in with the thousands of post on this subject,

I'm not dicussing the problem posed by the OP, which was well dealt with by djb, and I'm not talking about thousands of other posts, only this;

A bush or bearing cannot in its own right cause a wheel to shake,

Which is not true.

had the OP posted just saying that he had vibration when he braked, it would have all come down to the warped out of true disc, one of the most common post on the forum

I agree, disc problems causing vibrations are very common, but, they aren't the only cause of vibration.

 

[The Rock]

A bush or bearing cannot in its own right cause a wheel to shake, the brake disk has to be out of true or the tyre out of balance to start it off in the first place. a worn bush or bearing will allow it to shake more, but cannot start it off in the first place

My money is on a combination of the lot. How's that for diplomacy?

I'd still have a good swing on all things rubber though.

Rock

 

[television]

Good luck to you in trying to make a simple job into something complicated just to show how clever you are.

Sadly what you say about all of the others parts do not add up to what has been the simple cure of just changing the disc.

If you are not discussing the OP faults then what are you on about, and I do not care on your view of my quote.

A bush or bearing cannot in its own right cause a wheel to shake.

Unless the bearing is shot, and if it was that bad it would have destructed long ago, but that is not the case on this post.

I dislike it when the fear of god is posted into a thread, when it is not necessary and not the case as shown in 99% of this type of post.

Also it has never been anything other than the disc when the steering wheel shakes when braking on the something like 100 disc sets that I have changed in my life.

You want an argument, go and have it on your own, or show me some post to back up what you are trying to say.

I am confident enough to say what I do on post here and elsewhere