ENSURE SAFE DRIVING - Pamasoftimages.fasep.it/TECH_TALKS_WHEEL_ALIGNMENT.pdf · of Wheel Alignment....

1DETERMIN PROBLEMS IN TIME

LENGHTEN THE LIFE OF THE TIRE

The inspection of the suspension is a critical part of the operation of Wheel Alignment. This gives the mechanic a good opportuni-ty to identify worn parts that could alter the structure but also an opportunity to identify, even with a simple glance, small pro-blems before they become “big” and “expensive.”

IMPROVE FUEL ECONOMY AND VEHICLE PERFORMANCEGasoline consumption decreases when the running resistance de-creases. A proper alignment ensures a correct parallelism of the wheels, which helps to minimize tire wear and rolling resistance. This, together with a properly inflated tire ensures maximum efficiency and lower fuel consumption.

IMPROVE DRIVING COMFORTYour vehicle “pulls” to one side, the steering wheel vibrates, you have to constantly act on the steering to maintain the correct upri-ght direction? These and other problems are generally solved by proper wheel alignment.

TRAVELLING BESTA proper alignment allows the suspension to do its job as intended by the designers. When all components of the suspension system are in the right position, the bumps in the road are absorbed ef-ficiently, so the car is more stable road holding and trip more comfortable.

It has happened to almost everyone to install a new set of tires at the same time and be with one or two worn tires before the others. In today’s vehicles, this happens either on the front and rear tires. The main reason for this tire wear is just a bad wheel alignment adjustment.

ENSURE SAFE DRIVINGA periodic check of wheel alignment guarantees a car in perfect running condition, with excellent road holding, giving also the opportunity to identify in time worn or defective parts that may affect the safety of driving.

Adjusting wheel alignmentextends the life of the tire.

Checking wheel alignment:saving beforeit’s too late.

More powerto the groundand lower fuelconsumption.

Wheel alignment set:comfortable ride, less stress.

Adjust wheel alignment: travel well.

Inspection done: safe driving.

To focus selling services rather than just tires, we publish a small handbook on the reasons for carrying out professional wheel alignment. We recommend to print and attach visibly in the store.

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to check (and sell) wheel alignment6 good reasons

Page available as poster cm70x100 on www.fasep.it

WHEEL ALIGNMENT

CONTENTS

Do you really need to measure SetBack?Step Guide to the choice page 4

Toe measurementHow Toe is measured on the FASEP wheel alignment system. page 8

Electronic turntablesExpensive option or key part of the aligner? page 10

Is FASEP a 6-sensors or an 8-sensors type?Wrong question: FASEP is more accurate and faster than any 6/8 sensors system. page 12

PSD or CCD sensors?What is the difference between PSD (FASEP system) and CCD sensor technology. page 15

3-Point-SyncroSelf-centering 3-point Syncro clampers. page 16

Contact clampsBe ready in a minute! page 16

FASEP measuring systemComparison with other measuring systems. page 19

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Theory and Practice of Wheel Alignment. For true experts.

What is Set-Back?SetBack is the angle between two wheels that are on the same axle. In the picture, the front right wheel is apparently “shifted ahead”. Measuring SetBack should mean answer to the question “whi-ch wheel is shifted from the original position?, and how much is that shift”? The value might be indica-ted as a distance (A) or as an angle (B) on the axis perpendicular to the axis of travel.

How Set-back affect the behavior of a vehi-cle (Picture 1)SetBack does not really change the behavior of the vehicle on the road. 4 parallel wheels still tra-vel straightforward, whatever their position. There could be other reasons for a car pulling: for exam-ple a different Caster between the right and the left wheel. Further on this later.

How Setback affect the behavior of a vehicle (Picture 2)The SetBack, also, does not influence the car good going on turns (the so called “rudder effect”). Actually, during the turns, the left and right wheels steer with different angles and on different centers and they are always one before the other with respect to the traveling direction (the wheel inside travels ahead with respect to the external). The picture 2 shows how the internal wheel travels ahead of the external by an angle B bigger then any possible SetBack angle. The internal wheel, when on turns, can be ahead of the other by several centimeters (or degrees, if we talk about angles).Obviously, the design of the suspensions takes this facts into account as they affect suspension performances.We can clearly see that the few millimeters (or tenths of degree) of the SetBack (if present) are much smaller then the “shift ahead” of the internal wheel (by various centimeters) thus, proportionally, the SetBack (if pre-sent) influence on the car behavior is negligible.

Just a “selling issue” ?If SetBack does not influence the car good going on the road or on turns, we wonder how measuring the SetBack could be useful.We may think, then, that it could be a “selling issue”.Let’s not go into marketing or patent issues, let’s continue talking on the technical side let’s answer the question: “what is SetBack useful for”?If SetBack does not help to find out the car behavior problems (specific wheel alignment measures may

Do you really need to measure SetBack?Step Guideto the choice

Picture 1How Set-back affect the behavior of a vehicle

Picture 2How Setback affect the behavior of a vehicle

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explain those problems!), we may hear someone saying that SetBack is useful to check frame problems and detect collisions.We then would like to change the question from “what is measuring SetBack useful for?” into “what is SetBack caused by?”

What is Setback caused by?The answers can be limited to 4 cases:

- the car maker- a collision- a different regulation of right and left caster- the wheel alignment measuring system itself

The last case may appear senseless, yet we have to ask: given a car with real SetBack zero, could we read a SetBack measured different from zero? Later we will try to explain why the answer is yes.

SetBack by design (Picture 3)Are you sure that cars have a perfect “rectangular” shape, as everybody imagine?

It is enough to measure the Left Wheelbase (PS) and the Right Wheelbase (PD) with a common meter-gauge to understand how much they are different in reality, even in a new car, simply because of the car maker design.There are a lot of examples and a lot of technical reasons.The most known case is the “torsion-bar spring” (not to be confused with anti-roll bar!) that we find on the front axle of Alfa75, Renault 5, Mitsubishi Pajero, Daihatsu Feroza or on the rear axle of Renault 4, Twingo, Clio.Generally, we can say SetBack is caused by design choices regarding the su-spension type (torsion-bar spring) or the transmission type (typical of the front traction with transversal motor).In these cases, it is possible to find really different dynamic behaviors, because of a difference between PS and PD of various centimeters (comparable to the difference of advancement of the internal wheel with respect to the external one; look at the picture).Once we “revealed” a simply forgot truth (PS differing from PD by design by few centimeters), we would like to ask:“if the car maker designs purposely a SetBack between wheels on the same axle, why there is no specification for the SetBack value from the Car Maker to see if the SetBack value is right or not?”and then“why there is not any adjustment directly on SetBack, as it is designed by the car maker itself?”We still continue to make you wonder: are you sure that you have to adjust or keep “under control” the SetBack, and that the car maker would leave a such important thing being wrong?

SetBack to detect a collision? (Picture 4)This is maybe the the most used argument by the “sales-men of SetBack”: “SetBack can show if the chassis or the suspensions have some problems!”

Let’s imagine that the car under examination does not have a SetBack by design, so that the “original” SetBack should be zero, we measure the SetBack and, when it is found different from zero, we should get some help about the chassis status.Of course, nobody is going to buy a wheel aligner to measure SetBack in order to fix a chassis bent because of the collision.It would be a lot better using a car-bench built right for that scope. But we may be interested to detect if our customer hit against the walkways or if he got hit and damaged the suspension’s elements.Let’s suppose then, for example, that the alignment indicates a SetBack of few milli-meters/degrees between right and left wheel.We now wonder which wheel is wrong. Unluckily it is not possible to measure the variation of the wheels from the original position, we can only measure the varia-tion between the right and the left one. So detecting which wheel is wrong looks rather difficult.Some Wheel Aligners do indicate which wheel is shifted. Actually, by admission of some manufacturers, they follow the rule that the left wheel is statistically more “protected” and the right wheel is the one hitting on the walkways: therefore they assume the left wheel position correct, and then indicate the SetBack po-sitive or negative for the right wheel.I think it is a quite weird rule.

Picture 3SetBack by design

Picture 4SetBack to detect a collision?

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To answer to the initial question regarding a possible collision that might alter the suspension status, we prefer to consider more exact and measurable values. Inclination, caster and toe are important indicators of the good status of the suspension, also to find some gross blunder caused by a collision.

Anyway, looking at the suspension plays before going for the alignment might do a much better job then a “top-alignment-system” that simply guess which wheel is wrong.

SetBack or just a Caster problem? (Picture 5)It is a weird thing to treat sinusitis with a medicine for the headache. But, on the opposite, we know that a sinusitis cure can represent the solution for the headache. Simply: to solve a problem, you better look for the causes of that problem, not just for the symptoms. This is the case of SetBack caused by a different caster between right and left wheel. If we want to take care of an headache (I mean the SetBack) it is possible we fail, but if we treat the real illness (a different Caster), the collateral effects (SetBack) may disappear.

In fact, depending on the suspension type, a cross-caster (difference between left and right) can cause a SetBack.

With reference to the suspension scheme shown in the picture, where the caster regulation is on the lower joint, directly connected to the wheel, while the upper joint does not move, it is easy to understand that a ca-ster regulation causes a SetBack different from zero because it changes the wheelbase. Of course, the Caster is the cause of SetBack and not the opposite. In the case of SetBack different from zero, it is better to check if Caster need to be adjusted before looking for collisions, etc. It would be like to take care of the headache instead of considering the real cause.

Obviously the Caster is one of the fundamental measures of alignment, which you can do with all FASEP aligners.

Set Back caused by the Clamping System. The Tyre changer Test. (Picture 6)Before we wondered if a car with real SetBack zero may result with a SetBack different from zero? We said the answer is yes.

As a matter of fact, the sensor which reveals SetBack is linked to the wheel with a clamper.

Generally the clamper is subject to Run-out, which is compensate by electronically. In this case all is ok. The value of SetBack will be shown by the computer scre-en and in this situation we refer to the three cases we explained before.

Recently, by the way, we may find in the market some clamps “run-out free” which help to avoid the run-out procedure to save time and preserve the original su-spension balance. According to the manufacturers these clampers do not need any run-out.

However, to check if the clamper (or the seller) tells the truth, it is possible to make the TYRE CHANGER TEST.

Keep a wheel with a good tire rim, possibly new, place it on a tyre changer turntable and lock it. Then take the clamper and attach it to the rim following the manu-facturer procedure. Now rotate the tyre changer turn-table and with the reference of a fixed point (your eyes cannot be sufficient) check the clamper oscillation in the point where sensors is attached,. Obviously we want to see that the clamper shaft rotates in the center perfectly. But we may be surprised!

There is a simple explanation: some clampers are de-signed to avoid run-out for angle offset (clamper and wheel stay parallel) but they do not maintain the ef-

fective center of rotation (clamper and wheel axis do not coincide). As a result, without run-out compensa-tion, some values are right (toe, camber and caster), and the alignment is correct, while some other values, such as SetBack, will result wrong.

Looking at the picture beside: the blue lines (vertical) indicate that wheel and clamper are both parallels, the red lines show that clamper axis is not the same on the center of wheel axis. Without making a run-out procedure, computer will indicate a SetBack that in reality doesn’t exist. The reason of this is the design of system, and it leads to the conclusion that with the “long arm” it’s necessary to do run-out if we want to see a real SetBack. Otherwise the Setback indicated might depend on the clamper and not from car.

Picture 5SetBack or just a Caster problem?

Picture 6Set Back caused by the Clamping System.

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The FASEP System, without SetBack, without SetBack problems (Pictures 7-8)So we now have a better idea of what is SetBack and where it comes from:

1. SetBack, as a change from car constructive conditions, does not really influence the car going on the road.

2. SetBack can be introduced by the car makers.

3. Car makers do not set tolerances or adjustments for SetBack.

4. it is not possible to identify the wheel in wrong position only referring to SetBack value.

5. SetBack can be a consequence of other Alignment measures.

6. SetBack can be introduced by the same Measuring/Clamping System.

Everybody can draw conclusions.Our conclusion is that SetBack is a fake measure, that does not help in any way going a better job.

That is why FASEP has designed a measuring system, avoiding SetBack measure and implications, with a lot of advantages.

The advantages are:- run-out not necessary in the majority of cases, thanks to clamper design and absence of sensor “long arm”.

- compact and easily-handled sensors.

- less necessity to level the sensors than in “long arm” sensors (in the case of “long arm” sensors, if they are not correctly leveled, Toe and Setback assume wrong values.)

- easy use of the sensors also in case of spoilers, big wheels or little wheels, lowered suspensions, etc.

Without SetBack. Only the FASEP System?Approaching the wheel alignment measures “along the car”, instead of “across the car” (I mean with front long arms that allow to do a transversal measure), is not a FASEP exclusive point of view. Other manufactu-rers did it the same way, measuring toe “along the car” instead of “across” and obviously on such systems there is not a Setback measure. Among others, we can mention:

- Policontrol (made in Switzerland, for control lines) now used by Bosch - Nussbaum aligners.- Powercontrol (made in U.S.A., for car manufacturer’s assembling lines)- B-Dyna (made in Japan, for control lines)- G-Swat (made in Japan, for control lines)

Picture 8FASEP measuring system, without SetBack

Picture 7FASEP measuring system, without SetBack

FASEP measuring system: without SetBack.

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Latest added to the “along the car” approach:

- John Bean 3D (Balco, Sun and Hofmann are the same machine)- Hunter 3D- Bosch aligner introduced in Automechanika 2002.

ConclusionsI am that when looking for buying a new Wheel Alignment system, maybe an expensive one, every cu-stomer was advised that buying a system without SetBack measure was a big mistake because SetBack measure was to be considered fundamental for a proper adjustment of wheel alignment.

And we are also sure that many of these costumers thought it was a true statement and possibly few of them based their buying decision on this particular fact.

Soon, when they will start looking for a new Alignment, they may hear that there are new great technolo-gies, 3D,etc., but there will be not SetBack.

So, was SetBack really useful? Finally, we would like to ask a question to the owners of a “long arm” aligners:

when you really wanted to make a good alignment job, in your experience, was Setback a critical issue you had to take care of? We should be glad to discuss the case under a technical point of view.

Toe measurementHow Toe is measured on the FASEP wheel alignment system.

rectangle shape chassistoe at 0°

In other words, in what direction are you aligning your car? Few customers are wondering about the “magic” way FASEP alignment system measures toe without any cross toe measuring arm.The fact is indeed quite simple when you think to the way an angle can be measured on a plane: you can measure it referring to x-axis (horizontal, or across the car) or y-axis (vertical, or along the car).So now please give us few seconds to explain how FASEP (and actually many other manufacturers) mea-sures toe on a car.In the end, what you are supposed to do is to align the car to its travel direction; something you may not have done so far.

The ideal case: a rectangle shaped chassis, toe=0° (Picture 1)The dashed line is the geometric centerline of the vehicle.Toe of the left front wheel is the angle between the wheel middle line (red) and the x-axis or the y-axis.In the case of a car ideally rectangle shaped, with all wheels at 0° toe, it is very clear how the real toe of the wheel (red line) and the toe measured on the sensor (light blue line) are giving the same value, that is 0°.

Figura 1Rectangle shape chassis, toe = 0°

Picture 2Rectangle shape chassis, toe ≠ 0°

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A little more complicated: rectangle shaped chassis, toe is not null (Picture 2)In this conditions, if wheel is with toe-in by 1°, it is easy to see that the sensor measuring toe along the car (y-axis) that is with respect to the sensor placed in the rear left wheel (light blue lines), is also giivng a reading of 1°.

Trapezoid shaped chassis, toe not null (Picture 3).In this picture, the chassis is no longer rectangle shaped, and become a generic trapezoid shaped chassis.In this case, we designed a front track smaller then rear track (usually it is opposite situation).The difference between front and rear wheels tracks is evidenced by the green lines.Displacement of the left rear wheel with respect to the green line (or, with respect to the ideal position of the rear wheel if the chassis was rectangle shaped) is called semi-track difference.The value of toe at the left front wheel against the centerline (yellow) is still 1° (red line) but angle “Beta” (light blue lines) measured by the front left sensor (in relation with rear left sensor) is not 1° because the rear left sensor is displaced to the right with respect to position in figure 2.However angle “Alfa”, given by the displacement of the rear wheel can be easily determined by measuring the (semi) track difference.Alfa + Beta make then the correct result of toe angle for the left front wheel.

Measuring toe “along the car” (or referring to y-axis). Only the FASEP System?Approaching the wheel alignment measures “along the car”, instead of “across the car” (I mean with front long arms that allow to do a transversal measure), is not a FA-SEP exclusive point of view.Other manufacturers are now doing the same way, reco-gnizing that measuring along the y-axis gives consistent advantages in measurement process and accuracy, not to mention the fact that a car is traveling exactly in the direction of the y-axis and there is where we want it to be aligned.

Among others, we can mention:- Policontrol (made in Switzerland, for control lines)- Powercontrol (made in U.S.A., for motoring assembling lines)- B-Dyna (made in Japan, for control lines)- G-Swat (made in Japan, for control lines)

Latest added to the “y-axis” approach:- John Bean 3D (Balco, Sun and Hofmann are the same machine)- Hunter 3D- Bosch aligner introduced in Automechanika 2002.

ConclusionsThe way I described things here is obviously following very simple cases and conditions of the car.More complicated cases can easily be described just in the same way, but taking in mind that Thrust Angle becomes important.However the main point to understand here is that an angle can be measured always with reference to a given direction.Traditional aligners do measure toe from one side the other on a car, what we defined the direction of x-axis, in other word left-to-right.

FASEP, since many years, and very recent aligners (3d generation) are instead using a different approach, getting the same reading referring to the y-axis, or , more simply, front-to-rear.Of course the way to measure the angle does not change the angle.But in all measuring systems you have always to take tolerance and accuracy into your consideration.The question is that your car is traveling along the y-axis, front-to-rear.So you are supposed to do this exactly: align the car to such direction. As simple as that.Now, wouldn’t it be better to place your measuring system in such direction instead of left-to-right, in order to align your car exactly where it has to be aligned, that is the travel direction?

rectangle shape chassistoe not null

trapezoid shaped chassis toe not null

Fasep measuring system use from long time a different approach, measuring long y axis, from the frontto the rear of the car.

Picture 3Trapezoid shaped chassis, toe not null

Semi track difference

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Electronic turntablesExpensive option or key part of the aligner?

Turntables are often offered as an option for wheel aligners, as if they might be used rarely or as if they might not be ne-cessary for an accurate wheel alignment job.FASEP offers electronic turntables on all computerized aligners as a standard fe-ature. Why?Few minutes to understand if buying a wheel alignment without electronic turntables is a good choice “as the job is good anyway” or if, instead, you are cut-ting out an important part of the equip-ment and you end up doing “half a job”.

Which alignment angles are measured with electronic turntables?Electronic Turntables are used to measure the following angles:1. Steering angle2. Toe-out-on-turns (typically at 20 degrees)3. Max steering angle (or Lock angle)

Why you need to measure steering-related angles?Steering angle. it is needed for the following purposes:1. to measure Caster angle (typically measured with a stee-

ring angle at +/- 20 degrees)2. to measure SAI (also known as King Pin) (typically measu-

red with a steering angle at +/- 20 degrees)3. to ensure accurate re-alignment of wheels after measu-

ring Caster and SAI

Toe-out-on-turns at 20 degrees. it is needed for the fol-lowing purposes: 1. to measure the difference in steering

angle between left and right wheel when one wheel is turned (typically at 20 degrees).Max steering angle. it is needed for the following purposes:1. to measure maximum steering angle left and right for each wheel (it is typically an angle between 30 and 40 degrees)2. to measure exact centering of steering gear box

How can you measure such angle without electronic turntables??As a matter of fact, in the past, Caster and SAI readings were done using a graduated scale on mechanical turntables: a “manual” reading was done.Caster and SAI, however, are the only angles that can be measured in such a way, that is with an accuracy of +/- 1 degree for the steering, even being more accurate is of course better.All other measurements (Toe-out-on-turns, lock angle) can only be measured with a good accuracy (as a matter of fact FASEP electronic turntables measure angles with an accuracy of +/- 0,1 degrees).Question is then :”how to measure Caster and SAI automatically without electronic turntables?”Until few years ago, answer was “impossible, you need electronic turntables”.Nevertheless, recently, most of wheel aligners are offering the possibility to measure Caster swing using toe sensors. This cut the costs of electronic turntables and let caster swing to be automatic.But.. when you cut costs, you may also cut something else..

Advantages and disadvantages of measuring steering angle with Toe sensors.The advantage of doing Caster swing using an existing sensor (the toe sensor) is logical. No need of a ad-ding anything new (the electronic turntables), no extra costs.

Advantages stop here.

Disadvantages show “how blanket is short”:

1. Caster swing measured at smaller angle then manufacturer’s specification: toe sensors have a li-mited operating range, typically +/-5 degrees, at best +/- 10 degrees. For this reason, Caster swing is done at +/- 10 degrees instead of +/- 20 degrees as it is required by car’s manufacturers. This increase inaccuracy of caster reading.

2. other measures are not possible: for the same reason that toe sensor’s range is limited to +/- 10 de-grees, all other measures (toe-out, lock angle) are not possible. To measure such angle, you must have electronic turntables.

Toe-out on turns at 20 degrees

20° 20°-x

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3. a big mistake in steering angle reading: toe sensors introduce a big mistake in reading the steering angle. See below this in details.

Inaccuracy and mistakes introduced measuring steering angle with toe sensor.Inaccurate Caster Swing: The first problem comes from the fact that you are measuring Caster swing at +/- 10 degrees whereas it should be measured at +/- 20. Measuring at 10 degrees (and usually the limit is +/- 7 degrees) means clearly that you double (or triple, at 7 degree) measurement inaccuracy, that is the error made in measuring the Caster and SAI angles.Measuring shift instead of rotation: The second problem is due to the fact that toe sensors are not “at the center of the wheel, or, to be more precise, at the center of the steering axis. On the opposite, toe sen-sors are quite far from the steering axis, typically 30-40cm (10in or more). This means that, when steering, toe sensor not only turns but also shift laterally. Picture on side side show this fact clearly. When steering, the wheel (thus the sensor) not only turns, but also shifts (shift is to the right, in the example) The red sector is the portion of angle due to the lateral shift, that the toe sensors anyway measures as a rotation. To be more clear: just look at the turntables when turning the whe-el. The plate not only rotates but also shifts laterally (that is why the turntables must also be free laterally!).Inaccurate steering angle:The sensor cannot separate the shift (left or right) by the rotation, therefore shift is taken as a steering angle by the toe sensors.This leads to an error of 1 to 2 degrees. Thus, measu-ring 10 degrees steering with toe sensors might be as inaccurate as +/- 2 degrees. The bigger the steering an-gle (10 instead of 7), the bigger the error. The shorter the car, the bigger the error.Measuring pure rotation with turntables:The problem described above happens only when using the sensors to measure steering angles.If you use electronic turntables, instead, no problem at all.Electronic turntables, actually, only measure the pure rotation, as they follow every movements of the wheel, including lateral shift.

How important is to measure steering angles (and do it well).The reason given to save a lot of money and allow a “small” error to go into the measurements is listed be-low:

1. Caster is not such an important measure2. Caster is not measured most of the times3. Caster swing does not need a high precision4. Steering angles are a “mechanic” job, not a tyre shop job.

These things might be part of the customer’s way of thinking, at the time of buying an expensive piece of equipment, where electronic turntables might be an expensive option.

Let me tell you this.1. tyre service is a “sudden demand” type of business. When season starts and cars start coming into the

shop, time is critical: you must run as the next customer is waiting. Wheel alignment check is usually added as a final check after changing tires, and it follow the same rule: quick!

2. wheel alignment end to be offered “included” in the price of tires. This is a wrong way of doing your job: you are not only selling tires, you are selling your expertise!

3. a wheel aligner is set to work for many years: looking at an immediate saving and letting your job to be a little more inaccurate, will let you be inaccurate for years. While what you need is “be fast and accurate”.

So now what? 1. customer satisfaction. Customer is happy about your job, right after changing his/her tires, not only if tires handle properly on the road (which is obvious as they are new, and in this respect there is probably no much difference between you and another tyre shop) but rather if car is globally handling properly, with no left or right pull and a straight steering wheel. To ensure this little two things, Caster measure is a key point.

Effective steering angle Mistake

sensor rotates and shift

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2. rapid alignment check. Rapid alignment check, mostly on the front axle alone, is due to haste, and it only let you see if tyre wear is ok and, provided you have a 4-wheel alignment, let you see if steering wheel will be straight. In few more minutes, measuring Caster would also let you see if the car is pulling on one side. Why not looking at Caster, while car is on the alignment rack, and make sure your customer will be happy about your job?3. importance of Caster. from statistics made possible by computerized wheel aligners, we calculated that only 4% of tyre shop measure caster. I must assume 96% do not understand how important Caster is.As you may know, Caster influence “return of straight steering wheel” after turns and influence the straight direction of a car in motion. When a car “pulls”, most of the times Caster is the problem.4. Precision in measuring Caster. car pulls if there is a difference in left and right Caster value. Accuracy of measure is therefore important as we need to know the difference between left and right. If you have a left measure and a right measure with a 0.5 degree tolerance, tolerance on difference between left and right is double. +/- 1 degree accuracy is not acceptable when measuring cross-caster.5. “mechanic” job? in today’s market, mechanic and tyre shop are set to mix. Mechanic shop are selling tires, tyre shops are becoming “quick service” selling brake pads, exhaust, etc.Measuring steering parameters of a car help to identify problems before it is too late, before they become expensive. Measuring steering related angles make sure your customer will find his/her car in perfect con-ditions after changing to new tires, from A to Z.

Conclusions: Question is always the same: a well done job pays always more then a half-done job.Are you sure your customer did not realize you were not accurate as he/she expected?

We are often asked this question. It might be just the wrong question.FASEP is a unique 4-wheels alignment system. More accurate and faster then any 6/8 sensors system.To make it simple, pretty much like 3D systems, FASEP alignment measure angles “along” the car, instead of measuring “across” the car.

1.The easy case (Picture 1)Let’s make a simple example with a simple measuring system.In the picture on the left, wheel alignment system is a simple 2-wheel alignment.In the picture you can see a simple case: wheels have 0 degrees toe (red), that is the wheels are “straight”, and the value measured by the system is also 0 (light blue) for both left and right wheel.

2. A little more complicated: wheels are “shifted” (Picture 2).If wheels are shifted (that is left wheel is not aligned horizontally with the right wheel) problems start coming.Let’s consider the picture.Wheels are still “straight”, that is both have 0 degrees toe (red), but sensors are measuring 1 degrees toe (light blue) with symmetric sign left and right (+/-).Real Total Toe is = 0+0 = 0 (red).Measured Total Toe = (+1) + (-1) = 0 (light blue).In other words: Total Toe is measured correct (0) so that tyre wear will be correct.Instead, by the measuring system depicted, Single Toe (left and right) is measured wrong (+/- 1 degree instead of 0) so that steering wheel will not be “straight”.

Conclusion: measuring toe “across” the car can lead to wrong measurement when you have set-back.

Is FASEP a 6-sensors or an 8-sensors type?It might be just the wrong question. FASEP is a unique 4-wheels alignment system. More accurate and faster then any 6/8 sensors system.

Picture 1The easy case

Picture 2A little more complicated: wheels are “shifted”

The shift between wheels is evidenced by letter A in the picture. It is normally referred to as “set back”. Please keep in mind that left and right wheel might be shifted due to several reasons (difference in caster adjustment, manufacturer’s design, collision, apparent shift *).

* apparent shift is the shift due to the wheel aligner’s measuring/ clamping system and not to the actual wheel position.

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FASEP measuring system:

along the car moving direction.

3. The easy case, measured with the FASEP system (Picture 3).Let’s see the example 1. again with FASEP system.FASEP system measures “along” the car.So reference is taken “front-to-rear” and not “left-to-right”. To make it easy, rear wheel angles are yet not considered, but the rear wheels are simply taken as a reference.

In the picture 3 you can see: • wheels have 0 degrees toe (red) that is the wheels are “straight”• value measured by the system is also 0 (light blue) for both left and right wheel.

4. Wheel are “shifted”, and measured with the FASEP system (Picture 4).Let’s now shift the left and right front wheels, just like in example 2. Wheels are still “straight”, that is both have 0 degrees toe (red). FASEP sensors, however, measuring “along” the car, are still measuring 0 degrees toe (light blue). No error.

Conclusions: With FASEP, Total Toe and Single Toe are measured correctly, even in case the wheels are shifted. This is the first point to see how FASEP can be more accurate then 6/8 sensors systems.

5. A more complete overview (Picture 5).Let’s now consider a more complete case.To make it simple, wheel are still “straight”, that is all wheels have 0 degree toe.In the picture, an 8-sensors system is shown and angles measurements are shown in light blue (to consider a 6-sensors system just remove the green line marked with B).

With an 8-sensors system, customers are often convinced that they can get also:- wheel base left (E) and right (F)- setback = E-F = (see also point A in figure 2)- front track (C)- rear track (D)- offset = front track (C) - rear track (D)

For Setback please remember consideration made in point 2: Setback MUST be measured in someway when you have an “across-the-car” type of wheel alignment system just like a 6 or 8 sensors type, to avoid wrong measurements (for partial toe). See also a more specific article: Do you really need to measure SetBack ?

For Wheelbase and Tracks measurements, just see below.

Picture 3The easy case, measured with the FASEP system

Picture 4Wheel are “shifted”, measured with the FASEP system.

Picture 5A more complete overview

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6. Same angles, different wheelbase (shorter car) - (Picture 6).Just see how it is absolutely impossible to get Wheelbase measured with a 6 or 8 -sensors system where ONLY angles are measured.

In picture 6, you have a shorter car, but still all angles have 0 degree, like in picture 5.So same angles, but a different wheelbase.

How can you measure wheelbase with an 8-sensors system with only angles measured?Just you cannot measure wheelbase. You can just estimate wheelbase, assuming that front or rear track is correct (is the one specified by the manufacturer).It is just a simple trigonometry calculation, but it is based on an assumption, not on a measure.

7. Wider tracks (larger car), same angles (Picture 7).Just see how it is absolutely impossible to get also Front and Rear Tracks measured with a 6 or 8 -sensors system where ONLY angles are measured.

In picture 7, you see a wider car, still all angles have 0 degree, like in picture 5. So same angles, but different front and rear tracks.

How can you measure tracks with an 8-sensors system with only angles measured?Just you cannot measure tracks.You can just estimate tracks, assuming wheelbase is correct (is the one specified by the manufacturer).Another assumption, not a measure.

So what? To measure wheelbase you assume tracks are correct. To measure tracks, you assume wheelbase is correct. Just too much. Did you pay for a measuring system or for an “assuming” system?

Conclusions: when you measure only angles, you have many different cars (longer/shorter or wider/narrower chassis) that can “fit” with the same angles. So you really can not know what are your car’s physical dimensions.

8. FASEP system: angles and distances to make exact measures (Picture 8).The FASEP system not only measure “along” the car, as explained in point 3 and 4.FASEP system is also based on two physical dimension (distances) of the car.Two REAL measures (front track G and rear track H) that, once entered in the computer, allow all calculations to be EXACT for that specific car, with no possibility of wrong results due to wrong assumptions that all cars are the same.

FASEP system is based on ANGLES (measured) and DISTANCES (G and H). Only one car can be the right solution.

Conclusion: everything is perfectly measured and identified. No wrong assumptions.

Figura 6Shorter car (than picture 5).

Picture 7Larger car (than picture 5).

Picture 8FASEP system: angles a+nd distances to make exact measures.

FASEP measuring

system: measures

always exact.

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End Users are usually obscure about what is behind a CCD-sensor or a PSD-sensor.This is a short guide to understand the two technologies.

1. What is a PSD?PSD (Position Sensing Detector) is an opto-e-lectronic device which converts an incident light spot into continuous position data. It provides outstanding resolution, fast response and excellent linearity, for a wide range of light in-tensities and simple operating circuits.The basic feature and advantage of a PSD device is that it gives continuous data readings.

2. What is a CCD?CCD (Charge-coupled device) is a sensor consi-sting of an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to one or other of its neighbors.The basic feature and disadvantage of CCD de-vice is that it is a matrix of On/Off sensors that are switched on and off by lights. 3. Why PSD is more accurate than CCD?Because CCD is a matrix of dots switched on and off, the resolution of CCD sensors depends on how many dots are located on the sensor. Typi-cally a linear CCD sensors has 1024 dots. Enhan-ced versions of CCD sensors have 2048 dots. Just imagine that modern digital cameras are using 2048x2048 = 4 millions pixels. 1024/2048 linear pixels correspond to a 10/11 bits digital resolution respectively.PSD is a continuous sensor, therefore the digi-tal resolution of a PSD depends not on the PSD itself (as it is “continuous” that is it has an infi-nite resolution) but on the digital system that “reads” the PSD.FASEP alignment sensors are equipped with a 16-bit digital conversion system, that gives a resolu-tion of 65536 points.This gives PSD sensors 32 to 64 times more ac-curacy then competitor’s products using CCDs.

4. Why PSD is faster then CCD?Because linear CCDs have a low resolution, ali-gnment sensors using CCDs have to be programmed to do multiple measures at every step to improve measurement accuracy and to lower measurement “noise”. To have the same accuracy of a PSD, CCD should perform no less then 32 measures and hence calculate the average measurement. Of course, it takes a lot of time to do 32 measurements in a sequence (even if we are dealing with milliseconds). Most designers would settle for 4 to 8 measurements to balance speed and accuracy. In these case you end up having slower speed from the sensors (4 to 8 times slower), and still less accuracy (8 to 16 times) then PSD.

5. So why CCD is preferred to PSD by most companies?Just consider these figures:- average cost of a PSD sensor = 50 USD - average cost of a CCD sensor = 8 USDAlso, PSD sensor need an expensive circuit design including Analog-to-Digital conversion.CCD on the other side is already “digitalized” so all it needs it is “speed” to make more measurements at the same time to improve accuracy

PSD orCCD sensors?

What is the difference between PSD (Fasep

system) and CCD sensor technology?

PSD sensor

CCD sensor

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The FASEP 3-point Syncro clampers have always been object of admiration from both clients and com-petitors.Normally our clients are amazed by their quality of construction and their obvious capacity of precise centering. Even our competitors ask themselves how we can permit ourselves the luxury of such high-quality clampers (and certainly expensive to be built!) in front of a market where price-policy seems often more important than quality. It’s right, that all FASEP wheel alignment system, from the less to the most expensive, are equipped with the same type of clampers.Obviously the clampers are most important to permit a precise measurement of the wheel trim and to

avoid useless and sometimes harmful compensa-tions. As a matter of fact, the run-out compen-sation introduces different negative factors: the time needed for the compensation of the clam-pers and the inaccuracy introduced in the mea-surement are the most important problems of a successful wheel alignment.

The FASEP clampers have been designed to grant two fundamental functions:1. the self-centering of the clampers on the tire rim2. the orthogonal position (90degree) of the axle (where the sensor is fixed) and the wheel.Just to give you some dates, the orthogonal posi-tion (surely the most important date) is perfectly controlled during the production process: every self-centering clamper has to pass a test which allows max. 0,15 mm tolerance on orthogonality.Also, if at a first glance they seem to be the same as years ago, the FASEP clampers has made an impor-tant evolution in the meantime. The last re-design has been completed in 2003 and a new design is actually in preparation for a further improvement.

The clamper allows centering on wheels from 10” to 21”.Thanks to the fast-fit clutches, it’s possible to re-place the adapters easily and quickly in order to, for example: to pass quickly from an iron wheel to an alloy wheel. Also, the clamp is ready for the installation of universal clampers (to fit the clamp on the tyre, rather then on the rim).

3-Point-SyncroSelf-centering 3-point Syncro clampers

Self-centering clamperwith fast-fit

Centered and orthogonal

on the rim

WATCH IT N ACTION

Contact clampsBe ready in a minute!

The FASEP alignment clamps have always been object of admiration from both clients and com-petitors. With Contact Clamps, FASEP offers now a great advancement. Speed of operation and accu-racy of measurements can finally go together. As a matter of fact, Contact Clamps are based on the idea of “acceptable tolerance”, that is strictly con-nected with the FASEP sensors design. When you consider wheel alignment, in fact, a number of factors affects accuracy of measures and accuracy of adjustments. The sensors measuring precision, clamping design, clamping method, clamps accu-racy (or clamping compensation accuracy), ma-nufacturer’s tolerances, mechanical plays in car suspensions, tire pressure levels, operator’s pro-cedures and operator’s accuracy of adjustment: all these factors affect the final result. Keeping the eyes only on precision of measurements or clam-ping does not help to improve general accuracy

of wheel alignment adjustment accuracy. With FASEP system (FASEP sensors and Contact Clamps) the “ac-ceptable tolerance” introducing a small loss of accuracy let us obtain great benefits in speed and general accuracy of the job!!

contact clamp in position

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As a matter of fact, the run-out compensation introduces different negative factors: the time needed for the compensation of the clampers and the inaccuracy introduced in the measurement are the most impor-tant problems of a successful wheel alignment.

The FASEP Contact Clamps have been designed to grant the parallelism between the wheel plane and the Clamp plane.

The orthogonal position (90degree) of the axle (where the sensor is fixed) and the wheel is ensure by the contact on the tire wall.

Just to give you some dates, the orthogonal position (surely the most important date) is perfectly control-led during the production process: every self-centering clamper has to pass a test which allows max. 0,15 mm tolerance on orthogonal.

The Contact clamps allows centering on wheels from 10” to 26”.

Thanks to the fast-fit hanger and tire-wall contact cylinders, it’s possible to fit on any rim, steel, alloy or with plastic protection with no problem.

As a matter of fact the Contact Clamps design works fine thanks to the way FASEP sensors do the measurements.As FASEP sensors only need to measure ALONG THE CAR and NOT ACROSS THE CAR, the result of measurements with Contact Clamps is always GOOD ENOUGH!

View from top

final assembly

contact clamps fitted with Extensions for LCV / trucks with exposed hubs

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FASEP system:measure is always

right even if sensor is displaced

competitor’s system:measure NOT exact

if sensor is NOT centered

View from Top. Use with FASEP Sensors. (Right sensor displaced)Even if right assembly not perfectly centered, because FASEP sensors measure only ALONG THE CAR, it is still correctly parallel and therefore the FASEP sensors can correctly do the measurements.

View from Top. Use with Competition Sensors. (Right sensor displaced)Because Competition sensor need to measure ACROSS THE CAR, as the clamp is not perfectly centered, even if it it is still correctly parallel, therefore the Competition sensors can not correctly do the measurements!

FASEP sensor centered FASEP sesnor not centered

Competitor’s sensor centered Competitor’s sensor not centered

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