dear all,

Due to numerous inquiries about wheel alignment on Porsche sports and racing cars, here are a few lines on the subject:

Wheel alignment on Porsche sports cars and racing cars

A Porsche 991 GT3 RS to adjust the axles for track use

One thing in advance:
In our company no "track adjustments" are carried out for 40 euros!

We carry out professional axle and chassis adjustments in relation to the vehicle and the relevant components of the axle kinetics of your Porsche sports car or racing car. All important parameters are included in the measurement of the axle geometry. Errors in the technical environment of the axle kinematics are thus excluded from the outset.

What does that mean for the work on your Porsche?

Before we measure and adjust the axle geometry, the following parameters are checked on your Porsche and, if necessary, adjusted and corrected, but we also replace defective components in advance.

The preparatory work for the axle geometry measurement is as follows:

- Check tires and air pressures.
- Checking the axle joints, axle carrier, tie rods and joints.
- Checking the steering center plane, the steering deflection to the right and left.
- Checking the spring domes and the #piston play of the shock absorbers.
- Checking the wheel bearings and their adjustment or bearing clearances.
- Checking the setting of the axle weights on our axle load scale.
- Checking the screws on all carriers, handlebars, stabilizers etc.
- Checking the rim runout, concentricity, radial runout, wheels and tires.
- Checking the steering stops on the steering gear

Only when all of the above parameters have been met and the components have been found to be "good"
let's start with the actual #wheel alignment and the #chassis adjustment of your Porsche.

On the following picture you can see the #rear axle of a Porsche #996 #Cup.


What should your vehicle be able to do after the axle adjustment?

Before each setting, we ask our customers whether they want to move the car in #normal street use, in mixed use, or in pure sport use at sporting events.

We then select the axle parameters accordingly, taking the tire brand into account, and recommend them to our customers.

Before #professional sports use, we prepare the Porsche racing vehicles in such a way that the weights of the drivers are included in the #measurement of the axle kinetics in order to optimally adjust the vehicles to the relevant driver and his weight.

All actual and #set values ​​are recorded by an #input measurement and readjusted or set if necessary.
All parameters are documented by us in a comprehensible manner for the customer before and after the #axis adjustment.

We check the following parameters and make adjustments if necessary:

1.) The front axle

Track ( #individual and total track, related to the geometric #axis ),
Camber (when driving straight ahead or zero track),
Wheel offset, related to the left front wheel,
Caster, spread and toe difference angle (determined together in a #turning routine).
2. ) The #rear axle

Track (individual and #total track, related to the vehicle's longitudinal center plane, formerly called the axis of symmetry),
driving axle angle,
fall
3. ) The axle geometry in relation to the body

rear wheel offset
wheelbase difference
offset right
lateral offset left
gauge difference
offset

These additional #measured values ​​named under point 3 are determined for control purposes. They can only be corrected to a limited extent by #adjustment work, because the #damage caused by violence is usually the cause here. To eliminate this, straightening work on the frame or the body is often necessary if the values ​​deviate too much from the permissible tolerances.

Basically:
If actual values ​​are determined outside of the tolerance, damaged parts must be replaced or adjustment work must be carried out.

If the values ​​are incorrect, the #rear axle is always adjusted first and then the front axle.

You have to know that the toe of the #rear axle has an immense influence on the toe of the front axle.

Basically, the following order applies here:
First the trail, then the fall, then the track.

Because the named values ​​influence each other,
has in practice this order in the setting
tried and tested by us for decades.


BACKGROUND KNOWLEDGE ABOUT LOWERING AND INSTALLATION OF WIDE TIRES

By simply lowering the body without further changes, the steering roll radius also changes.

An uncontrolled change in the roll radius has negative properties for the driving behavior.

This change is at the expense of the negative scrub radius.
In addition to brakes pulling on one side, a positive steering roll radius also means that the vehicle is pulling heavily on one side

Consequence.
Changed suspension strut positions change the spread angle, it increases and thus has a positive influence on the roll radius, which in turn has an effect on your changed braking behavior.
In addition, the wheel load on the wheel bearing is increased, which promotes wear on the wheel bearing.
By simply lowering the chassis, the #fall also changes to #negative. This also influences the roll radius and, as already described above, also affects the braking behavior. In addition, this also results in a change in lane, which can have the known effects on tire wear, one-sided pulling of the vehicle, faster turning in with toe-in and poorer straight-line stability with toe-out.
The wheelbase is also changed by chassis installations and conversions. This favors driving comfort with a long wheelbase. A larger wheelbase reduces the pitching motion of the vehicle and swaying on bumpy roads.
The caster changes to the positive after installation. This has a positive effect on the steering's restoring forces; it is raised more on the outside of the curve. The camber is therefore more negative on the outside of the curve, which noticeably increases the supporting forces.
The wider tires result in better traction when starting and greater cornering security, which is canceled out by the harder chassis.
In summary, it can therefore be stated that when installing a lowering chassis, all wheel control variables are strongly influenced:

Toe, camber, spread, caster, roll radius. It is essential to make adjustments to the axis kinetics afterwards in order to generate a positive effect!

The simple installation of harder springs is to be expected with considerable disadvantages for driving behavior. The problem is that not all axle parameters can be set on some Porsche vehicles.

As a result, structural changes would result in incorrect positions that can no longer be corrected. Just mounting a harder chassis has a significant negative impact on handling and road holding in general. This results in poorer grip when cornering, on uneven roads, loss of traction when starting and a noticeably increased risk of aquaplaning in the rain.

We have been working with the following formula for decades: "As soft as possible, as hard as necessary".

This applies equally to racing operations, as well as to the sports driver at track days!

As always with questions:
Just contact me.

Many greetings
Jurgen Albert