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European Car Magazine - GTV6 Project

 

 

Part 6 - Camber modifications & notes on alignment geometry

European Car Magazine - August 1995

Author - Paul Mitchell
Photos by the author and Peter Wu

 

You've performed all the suspension modifications on your GTV-6 or Milano that you thought were possible - new shocks, lower ride height, higher rate rear springs, larger diameter sway bars, performance bushings and a good alignment.  The handling is superb, but you find that the front tires are wearing unevenly.  The inside of each tire is wearing more than the outside.  There are no other signs of uneven wear; the car tracks straight, there's just this bald strip on the inside of your front tires. Upon returning to the alignment shop, you're informed that the wear is caused by excessive camber, several degrees of it, the result of low lowering your car.  
 
On the cars spun-off of the 116 Alfetta chassis-the GTV-6 and Milano, Alfa Romeo provided for camber adjustment, a first for Alfa for some time: Through the simple method of adding or subtracting shims from the lower A-arm at the subframe, a range of adjustment of several degrees is available.  Sounds like just what you need at this point.   Unfortunately, now that you've lowered your car, you've changed the geometry slightly - just enough to not allow you to dial out the negative camber.  

Now at this point many assumed that there was nothing that could be done to remedy the situation and allow them to enjoy their newfound performance to the fullest.  Few things are as discouraging as knowing that when it's time to replace your front tires, they will have 70% of the tread remaining on the outer half and be almost to the cord on the inside edge.  To further torture you, the front tires will certainly need replacement more often than the rear tires under these conditions.  It's difficulties such as these that can cast doubt as to the wisdom of the decision to modify your car, thereby ruining an otherwise enjoyable experience. 

Luckily, the solution was always right under your nose - under your car, actually. After a thorough examination of the front suspension, you'll find two spacers between each lower A-arm and the subframe. It is at  these spacers where the adjustment shims are placed to correct the camber when at stock ride height.  You don’t need a degree in engineering (though this shouldn't be deemed an excuse not to get one) to see that by reducing the thickness of the spacers, you can recover the lost camber adjustability.  

This modification was brought to our attention by the proprietor of Omega Motorsports, Rex Chalmers.  After patiently listening to our complaints of tire wear (and complain we did, as we have also another car; a 3.0 Milano suffering from this problem), he suggested this as the solution. 

After going home and getting up the nerve to undertake minor surgery on the front suspension and assembling the proper tools, we found that the job was far easier than it first seemed.  The only special tool required is the lower ball joint separator; # ST 60, available through AR Ricambi for approximately $38.  The rest of the tools are just simple hand tools that you'll find listed in the Tech Procedures.  The entire procedure should require no more than three hours to complete.  Afterward, the car will require a front alignment to set the correct camber, and this should be the last one you’ll need for a while. 

Having completed the modification, I can say that our tire wear is now normal and that the procedure was well worth the effort.  Should you choose to have the procedure done by a garage, the labor expense will easily be offset by the extended tire wear you'll receive after this modification. 
 
 

Required Tools

 

  • 13,14,17,19, 21 mm-Box open wrenches
  • 13, 14, 17, 19, 2 1 mm-Sockets and ratchet with extensions
  • Ball joint removal tool #ST 60, available through AR Ricambi
  • Hacksaw with several flne blades
  • Vise
  • File
  • Floor jack with jack stands
  • A ruler with graduations in inches

 
 

Alignment Specs - Alfa GTV-6, Milano

 

  • Toe-in-0.04 inches in
  • Camber-1/4 degree negative
  • Caster-3 degrees

     

This is a picture of the spacer - marked for trimming 5/16" from the small end.   

   

Tech Procedures

  • Begin by placing the front of the car on jack stands and remove the road wheels. 
  • Loosen and remove the bolts retaining the sway-bar links and remove the links.  Slacken and remove the bolts securing the shocks to the lower A-arms and free the bottom of the shocks.  It is not necessary to completely remove the shocks from the car, only the bottom must be loose.
  • Remove the cotter pin and loosen the nut securing the lower ball joint to the lower A-arm.  Using the ball joint removal tool, free the A-arm from the ball joint.  Using the floor jack placed under the A-arm, lift the A-arm to clear the ball joint shank.  The A-arm is now free of the other suspension components and has no pre-load. 
  • Using two 19mm box open wrenches, loosen the bolts securing the A-arms to the subftame and remove the nuts.  Pull the a-arm outward,, allowing the two a-arm bolts to clear the subframe.  The spacers may now be removed from the bolts.  Care should be taken to ensure that the A-arms do not slip off the torsion bars.  A prudent move would be to mark the indices and the corresponding splines with paint or a marker.
  • Take the four spacers and measure 5/16 in. in at the small end of each spacer taking care to ensure that the mark made is an even 5/16 in. around the circumference of each spacer.  Place a spacer in the vise and begin to cut along the mark made.  Be careful to cut straight, though a perfectly smooth cut is not absolutely necessary.  An alternative is to take the spacers to a machine shop and have them cut the 5/16 in. off with a lathe.
  • Once the spacers have been cut, finish the cut edge with the file.  Replace each spacer on the A-arm bolts and reassemble the front suspension.  Reassembly is the reverse of assembly.  Should the A-arm contact the subframe due to the reduced spacer thickness, an alignment shim of 1/32 in. may be inserted until you reach the alignment shop.
  • Once the suspension is reassembled and the road wheels replaced, the car should be aligned  immediately.

 
 
 
 

Notes on Suspension

Judging by the questions in the Tech Letters we've received, apparently our readers have been giving great thought to what's been previously written regarding suspensions and their modification. Hopefully this will help put to rest some misconceptions and illuminate the difficult process of setting up a performance suspension.  

A debate still rages over what the preferred suspension "hot set-up."  One camp believes that increasing spring rates 1.5 to 2 times the stock rates and substantially increasing the dampening rates of the shocks is the correct method for controlling body roll.  The other group insists that the preferred way to control body roll is with stock or close to stock spring rates and dampening rates, and substantially larger Sway bars.  Both methods usually involve lowering the car to some degree, and we'll discuss that later 

Keep in mind that the purpose of having a suspension is to keep the tires in contact with the road surface when that surface is less than smooth.  Most engineers involved in racing will agree that the first setup - the one composed of essentially stiffer springs and shocks - is basically a step backward in design and will markedly affect the handling negatively in real-world driving.  As we all know, the real world is full of bumps and potholes, figurative and  literal. When encountering these bumps and such at high speed while cornering, a too stiff suspension can cause the tire affected to lose contact, with possibly disastrous results. 

The other system to control body roll - relying primarily on sway bars - allows the suspension the compliance to follow the irregularities in the road. This is crucial in cars with MacPherson-strut suspensions, and less so on cars with well-designed un-equal length A-arm front suspensions. 
This allows substantially higher cornering forces to be generated over rough surfaces, and significantly    increases  safety.  Remember, the sole purpose of a sway bar is to limit body roll, and within certain limits it will not affect suspension geometry.  Sway bars should be sized to provide neutral handling.  The spring rates should be stiff enough to prevent the suspension front bottoming out, but no higher, and the  dampening resistance must prevent spring oscillations over irregularities, but again should be no higher. 

The one potentially significant drawback to sway bars will not become a factor if the sway-bars are properly designed and employed.  If the bars chosen by a hypothetical, misinformed owner are so large (more is better, right?), the advantages of independent suspension are lost.  In this Situation, when only one wheel encounters a bump, the force compressing the suspension at that wheel will be transferred by this 
overly stiff sway bar to the wheel on the opposite side-in essence turning your previously well-designed suspension into a live axle. If the sway bar size had been increased within reason, this problem would never 
have been encountered.  Obviously, there are limits to bar size.  The stiffness of a bar is increased by the fourth power of the increase of diameter (a bar with a diameter of 1 5/16 In. is almost three times stiffer 
than a 1.0 in. bar), so it doesn't take much of an increase to make a difference.  

When considering lowering a car, the goal most of us are trying to achieve is simply a lower center of gravity.  Unfortunately, often you can end up changing the geometry of the suspension to the degree that you introduce new problems that are far more difficult to remedy than correcting body roll with a reduced center of gravity.  I won't go into roll center geometry theory here, but some cars are so designed that their roll center is close to the margin already, and any change in ride height will be detrimental.  Correcting this requires major suspension surgery, so it follows that the best method for avoiding this situation is to calculate the roll center of your car before it's lowered.  Then only lower to a point within the range of proper roll center geometry, leaving a margin for maintaining correct geometry under full jounce.   As with all modifications, planning, and moderation are called for. 

 Of course, for the average owner, all of this may be moot.  Alfa Romeos are renowned for delivering outstanding cornering, while still exhibiting substantial body roll. They have been able to accomplish these seemingly mutually exclusive feats by having extremely well located rear axles (live axles, surprisingly) and a properly designed un-equal length A-arm front suspension.  So, for some, this debate holds no personal significance; they find the body roll entertaining. For myself, I prefer less body roll and so was drawn into the fray. 
 
 

Thoughts on alignment

Once your Alfas suspension as been improved through all of the modifications listed in this series, including the camber modification, you'll need a wheel alignment. To skip this last step is to throw all of your effort and money away.  You’ll continue to throw away money as your tires wear unevenly. What specifications do you align the suspension to?  Obviously the original factory specifications were for an unaltered car.  

The alignment, will not only affect the tire wear but will also have a significant effect on the feel of the car and the handling, particularly turn-in and transitional handling.  

These specifications were determined through use and testing and will fall within those that are generally accepted for performance street use.  If aligned to these specifications, tire wear will be within acceptable limits as long as the car's bushings are in good repair and there is no previous frame damage. 

First let's look at camber.  Some would have you believe that a negative camber setting of from 2 to 3 degrees is preferable for a performance car.  Not only, is tire wear going to be excessive, but a condition known as camber thrust occurs.  This will cause the tire to turn in the direction it's leaned, just as a bicycle will turn in the direction it's leaned.  To correct for this extreme camber, the toe setting must be adjusted to toe out, again causing another situation for excessive tire wear.  The camber should never be set over 1 degree for a street performance car, and the preferred setting is degree negative for the GTV6 with these 
modifications.  

Caster is another adjustment that has a significant impact on the feel and handling of the car, but usually has little influence on tire wear.  Most overlook the caster setting and its ability to fine tune their car's handling.  Caster can be used to increase or decrease the low-speed steering effort, high-speed stability (the willingness of the steering wheel to stav centered at speed) and turn-in characteristics.  More caster will increase steering effort and high-speed stability, and less caster will provide lighter turn-in effort and easier transition when cornering.  The caster can be adjusted to within a small degree to fine-tune your suspension to suit your driving style and the conditions of use-all of this while having essentially no effect 
on tire wear.  In consistent high-speed use, more caster would be beneficial, and use on tight canyon roads or autocross would call for less.  Of course, a compromise between the two is what most owners need, and 3 degrees of caster is what has been found to work well on our project GTV-6 under all conditions. 

Lastly, there's the toe setting, which can significantly affect both feel and tire wear. Generally, on rear-wheel-drive cars, the toe is set very slightly in to compensate for the tendency of the bushings to give, allowing the wheels to shift rearward and outward under the friction created by the vehicle moving forward over the road surface.  Setting the  toe-out slightly will result in quicker turn in and faster transitional handling, but will also result in increased tire wear.  With the GTV6, and its already quick turn-in, the toe should be set at 0.04 in to the inside.  Tire wear at this setting will be acceptable and the suspension design allows for very little longitudinal compliance within the bushings, so the amount of toe-in is minimal. 

When considering a shop to perform the alignment, care should be taken to ensure that the shop be capable of performing the Job properly.  Since it's most likely that you won't be receiving any parts back, you’ll just have to take the mechanics word that it's done right.  If it wasn't, you went know it until the tires start showing uneven wear – at which point it will be too late to recover, the lost tread wear.  All that can be done is re-align the car and hope it is done properly. 

Don't even bother trying to get the shop to pro-rate the tires for the tread lost between the alignments; they went do it.  Maybe I'm just cynical, but its been my experience that they will find every excuse not to pay  up.  The best course of action is to have it done right the first time.  Don’t be swayed by a shop's latest whiz-ban, laser liner alignment rack - the job can be just as accurately done by for -year-old equipment, which is what we used on our project car.  The most important thing is to have a technician you can trust to do the job right.  An easy way to gain piece of mind is to have him show you the readings on the equipment as each adjustment is made. 
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