Axle Alignment 2
The advice, in the case of axle alignment, not to rely totally only on the pure measurement values, but also to consider the visual examination, your impression and theapplication of a sound knowledge of the various
suspension types to find the error, should be the procedure used in all vehicle-areas.
Nevertheless, problems with the suspension have the effect of permanently disturbing the driving pleasure. Apart from that, they are difficult to pin-point using testing devices, searching for the error by computer
seldom brings the required results, over and above this, the problem is difficult to check by, e.g., test driving the vehicle. Therefore, it is wise to protect the suspension by adopting a considerate driving manner and not
to provoke trouble by mounting add-ons from uncertain sources.
Sometimes the preparation for testing is more complex than actual implementation. Of course, directly before the aligning, the vehicle springs should not be expanded. Should respective work have been carried out,
please do a thorough test drive. By the way, in the following text we are assuming problems, which cannot be solved by a standard axle alignment.
Then, we have a very good look at the tyres. We check the air-pressure and the road-contact surface. Here you can read up on the problems which can appear and how they are to be interpreted. Very often overlooked,
is the comparing of the measurements of the individual tyres and rims, inluding the apparently unimportant depth of the rim-bowl. If there is any suspicion at all, that the rims are not standard, check the stud-hole
pattern and the centering.
Now you can examine the suspension itself. This includes the guides, their structural joints and the rubber mountings. At this point there should be a tyre-lever at hand, to be able to apply enough force to change the
position of a mounting. Any play at all here, is absolutely not permitted. In there steering, or the wheel bearings, a very small amount of play, or none at all is permitted.
In this situation the shock absorbers can only be visually checked, whereby, a very small amount of oil-loss can be tolerated. Should the vehicle be in the correct position for the aligning, the use of weights is very
important. Ideally, they are to be placed in such a way as to simulate the normal use of the vehicle, in doing so, the problem(s) are noticed sooner. In this case, it is helpful to ask the customer how the vehicle is
The operating instructions of the tester describe the remaining preparation work. Of course, we assume that the testing surface is level and horizontal. Should the testing device suggest, before we start, a
compensation by rolling the vehicle forwards or backwards, this should be done just as conscientiously as the reading out of the values later. Also, in this respect, modern testing devices will not tolerate slovenliness.
The display showing the track can be used to check the center position of the steering wheel. Any repairing here, e.g., by laymen, is prevented by the fact that one often has no idea how the airbag works. Should the
track- and camber values be correct, and if the tyre-wear pattern also shows no abnormalities, the problem can be more easily localised. If the values are not conform, either the settings can be changed, or, if they're
not available, the respective part can be replaced.
In the event that no problem has appeared up to now, the caster and the splaying of the wheel position when cornering, are to be checked on the test bench. Should this be the reason why the customer is not
satisfied, in the case of a front-wheel drive vehicle, one should not forget the influence that a possible defect in the drive shafts can have. As always, one must ask the customer if the problem appears when
accelerating. Whereby, with rear-wheel drive, the influence of the (distinctly) higher caster is more important.
We are not only searching for values which are outside of the tolerances, we also compare the two sides with each other. Greater differences can, e.g., cause the vehicle to tend to pull to one side. By the way, one
should, after questioning the customer, be sure that the problem described has nothing to do with the braking system, otherwise at this point, quite different testing must also be carried out.
While we're on the subject, it is always advisable to ask about possible accident damage and the (perhaps clumsily) carried out repair work. Since without an accident having occurred, e.g., the splay can actually not
fall outside the tolerance. Now we are right in the middle of the steering system and, above all, the (possibly varying) re-centering forces. At the latest, the measuring ends with the steering offset radius and we find
ourselves exclusively in the constructive area. Apart from from the rim-depth and the possible widening of the track, assuming there is no accident damage, we don't have a great deal of influence here.
Should values have been changed during the alignment, then, at least parts of the measuring must be repeated and not only the particular measurement values of the parts concerned. Thus, it is certain that the track
will change, if work has been done on the camber. Despite all these meticulous tests, there can still be error sources. What about, if the rear- and the front axle are not in alignment? Basically, all the measurements
taken up to now, could still be inside of the respective tolerances.
Be critical, particularly then, if you suspect (concealed) accident damage. Take your measurements on all four wheels instead of on just two. Take into consideration that zero-positions have possibly, not been
adhered to. What's the point of, e.g., a light adjustment, without having a zero-position? In this case, the blame can lie with a non-functional electronic steering intervention. Sometimes, the only thing that helps, is a
pause for thought … 09/10