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MG MGF Technical - Camber
|I've recently had my F's tracking checked by my dealer. I'd noticed that the steering wheel was slightly off-centre to the right, and this was exaggerated during hard acceleration when I had to turn the wheel more to the right to maintain a straight line. The car's come back with no change to these characteristics. I have the before & after tracking settings which are all within limits, including thrust angle (0 deg, 0 min), except right rear camber which is just under minus 2 degrees (same before and after) when range is -1deg30 to -0deg30. I realise camber is affected by ride height and I've noticed that when parked there is sometimes a discrepancy between front and rear height on the right (front higher by up to 20mm) whereas on the left the front usually equals rear. I wonder if there is a fault with the rear right hydragas unit which is both causing the incorrect camber and the above handling characteristics. Or is the handling trait I describe normal when driving on the left on roads which generally slope down slightly to the gutter? Any thoughts welcome.|
|Sounds as though the thrust axis (the direction in which the driven wheels push the car) is off some how.|
Get the dealership to check the subframe alignment.
Is the car new or do you know if it has ever been involved in an accident?
Camber is unlikely to cause these problems- toe angles would however...
|Thanks for your thoughts Rob. I bought the car new a year ago and it hasn't had any accidents since then - and I hope none before! The car's been back a few times to get the suspension height adjusted (either too high or too low) and had the tracking done once before, after which it seemed to handle fine (but with height at 340mm rather uncomfortable in London - is this a record for the lowest set by a main dealer?!). As I said, the thrust angle shown on the tracking printout now is 0deg0' - does this mean the subframe alignment is OK?|
|>I'd noticed that the steering wheel was slightly off-centre to the right, and this was exaggerated during hard acceleration when I had to turn the wheel more to the right to maintain a straight line.|
-30 Minutes camber difference isn't that dramatic (IMO)
Mark, you mentioned about direction change under hard acceleration. How is it under smooth acceleration and decelleration in a high gear ?
Did the dealer check the ball joints of the front lower wishbone and also on any play in the rear adjustable lower wishbone ?
Those are prone to fail, even at some young cars.
Also any failure at the steering rack joints can be the reason. There is a modified spare part availiable to cure such problems in special cases. (More analysis required)
|Any uneven tyre wear may cause the steering wheel to become off-set and I would have thought could effect how the handling feels. I know my front tyres and unevenly worn and the steering feel on my car is not that hot ATM.|
|Hmm, if the car isn't handling correctly, then I would have to doubt the last set of tracking figures. It is possible that through operator error, the laser alignment modules may not have been mounted on the wheels correctly.|
I think what I'd do is to get the tracking geometry checked again. If everything really IS okay, then get the sub frame alignment checked- which is not something that can usually be checked properly on a laser tracking rig. The dealership should have the necessary information for them to do this.
Perplexing problem. :o/
|>Hmm, if the car isn't handling correctly, then I would have to doubt the last set of tracking figures. |
Of course. Also related to Pauls hint. If the tyre wear is the reason for a steering wheel offset, than at first the tracking was out ;-)
>It is possible that through operator error, the laser alignment modules may not have been mounted on the wheels correctly.
Here are som probably failures.
- laser modules must be centered on the rim by turning them in three different agles and fixing the module at an average point. Provides failure correction of uneven rims.
- If the steering lock was done wrong, than steering wheel will also stand cambered after the alignement got done.
Anyway, Mark, check the front wheels for any play. Lift the car at each side and rattle at the wheels. If there is play, than a ball joint of the lower wishbone is worn.
Found the same failure yesterday at Nikolajs MGF when he visited me for an analysis of nearly the same problem. (Rob, you know whom I mean).
In Marks case my thoughts go still in the direction of a worn rear lower wishbone ball joint.
>>>I'd noticed that the steering wheel was slightly off-centre to the right, and this was exaggerated during hard acceleration when I had to turn the wheel more to the right to maintain a straight line.
I had the same thing (except in the other direction), and it *was* solved by my re-track. One rear had been toe-in and the other way way toe-out. This, I assume, was trying to drive the back of the car off the road. Are you sure your new tracking values are correct?
>>>I've noticed that when parked there is sometimes a discrepancy between front and rear height on the right (front higher by up to 20mm) whereas on the left the front usually equals rear.
As with all my comments, please consider my relative ignorance, but if the F and R on one side are the same but the F and R on the other are different, then doesn't that mean that either (1) the car is on uneven ground or (2) the car (subframe?) is actually 'warped' somehow? Surely the four wheels should be in the same plane when the car's on level ground?
Does that make sense, folks?
|>>(1) the car is on uneven ground or (2) the car (subframe?) is actually 'warped' somehow? <<|
(1) is certainly true, but (2) needn't be. The hydragas links (what we often refer to as knuckles) may be trimmed by adding height with shims. If this process has been performed incorrectly, then it is entirely possible to have completely different heights for each of the 4 wheels.
This actually isn't too much of a problem as it really doesn't effect the handling that much. Of course, it is as irritating as hell to look at once you know there is a difference! To get these kind of problems properly sorted, you need to have your car seen to by a suspension specialist- and certainly Techspeed prepared cars are beyond reproach. :o)
You mention that on one side the ride height is the same both front and back. The ride height should differ between the front and the back, the back being slightly higher than the front unless I'm mistaken. One of the guys (Dieter- what page do you have it on?) will be able to tell you the correct ride heights front and back.
|Sorry, Rob, am I still being thick here?|
Surely if the top of one wheel arch is higher above the (level) ground than the other *three*, then the body of the car must be twisted?
8-/ 8-/ 8-)
|You are certainly not being thick there David as you are ofcouse quite right: if one corner has a higher ride height, then the ride heights for each of the other corners will be upset to some greater or lesser degree. The problem is that we haven't got accurate figures of Mark's car's ride height for each individual wheel to make anymore of a conclusion. :o/ Fortunately, twisted car chassis is relatively uncommon, but this would be highlighted by a full chassis alignment check.|
IMO, far more likely is the shimming of the hydragas knuckles.
|>>>>To get these kind of problems properly sorted, you need to have your car seen to by a suspension specialist|
Er, yes, probably true, but really one would have hoped that a MGR dealer would *be* such a specialist. In a similar vein, I assumed that I'd have to pay B&G to sort out the tracking (etc.) on my new F, but really, when you think about it, that's a bit sad, isn't it!
|I'll correct myself, the front should be about 4/5mm higher than the back.|
Here is the page from Dieter's website with the height settings for a standard car,
|>>but really one would have hoped that a MGR dealer would *be* such a specialist. <<|
Fair comment, but I haven't found an MGR workshop that is prepared to spend the time to really sort these problems out. Having said that, I wouldn't want to pay labour rates at a main dealer, and would only ask there assistance if covered by the warranty...
David, you are quite right, MGFs should have a 'nose-up' attitude. Mine however is completely the other way round, as a number of other F's about. Don't ask me why though!
|Thanks to all of you that have commented on my car's problem. |
David B - the point you make about one wheel being at a different height from all the others has perplexed me for a considerable time as you would indeed think that this would not be possible if the chassis was OK. Looking in the archive mine is not the only F to suffer this, although I'm uncertain whether a common problem existed in the other cars. As the problem is variable rather than fixed (see below) I can only assume that there is a bit of flexibility in the chassis, as you might expect with an open-top car.
Typical susp height meausrements now are:
Front R 368
Rear R 345
Front L 368
Rear L 365
The R front/rear difference is accentuated if any extra load is put on the rear causing it to squat, e.g. reversing into a parking space and braking, or parking slightly uphill, or even normal parallel parking, yet the left stays remarkably constant. If, however, I drive the car over level ground and very gently come to a halt with minimal braking then the right side values are F358 and R355.
I suspect the right is then lower than the left because the dealer just measured the front height when the front/rear discrepancy was there - as you can see it would then be 368 front R and L. I also suspect the rear camber was out because of the low rear height. My theory about the handling problem is that the right rear suspension tends to squat when I accelerate, pushing the front right up and necessitating a steering correction to the right.
Well, it's only an idea - I'm no engineer and everything I've learned about the F's suspension is from this BBS. Certainly I think the dealer needs to check subframe alignment after your comments, Rob.
When I have time I'll be taking it back to the dealer for them to try and sort it out (still under warranty).
|I'd be interested to know what the eventual verdict is on this one.|
If it had been a horse it would for sure been shot !
Could it bee as simple as a missing spacer at the rear R ? Out at the wheel the resulting change is about 4,5 times any height change at the knuckel in the hydragas sphere....Spacer is around 5 mm , do not have any at hand to check at the moment but should turn up as 20 - 25 mm diff at that place.
PS. Do You know any old racer that have eq. for checking corner weight ? Would be very interesting to know figures !
Regards , Carl.
This thread was discussed between 19/05/2001 and 22/05/2001
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