Case Studies

Porsche 911, 912 and 914 – Steering Tie Rod Upgrade Kit – Conversion To Turbo Tie Rods

First off, if you don’t know much about steering tie rods, the basic definition is that it connects the steering rack (in this case, a gear-driven box that translates turning the steering wheel into side-to-side motion to turn the front wheels known as a “rack and pinion”) to the wheel hub assembly (brakes, rotors, wheel, tire, etc.). It “ties” the track to the wheels.

The steering rack is up in the car’s underside, and the wheel hubs both turn and go up and down. So you need something that “ties” it together but can also handle all this movement. So it becomes a very fancy thing that needs two joints to be able to handle the movement. It could be a solid, straight bar if it didn’t have to move up and down and change the angle of motion. But it does. So we have two joints on it to do its job and manage the angles.

Original Porsche Design
On basically all Porsche 911, 912, and 914 models from 1969 through 1989, the tie rods look like the one shown below in the “Old vs New” photo. The exceptions may be cars already serviced and updated. The old tie rod has a normal ball joint at the wheel side (the “tie rod end”) like the new one. But at the other end, the old tie rod has an angled hinge-type joint with rubber bushings. On the outer end, which attaches to the wheel spindle, is the traditional tie-rod end with a ball and socket-type joint on the suspension upright end.

Why Update Needed
However, on the steering rack end, the inner tie rod is a strange-looking joint that houses a rubber bushing. Porsche designed this to help quell steering wheel vibration on their sports cars and installed this rubber bushing rather than the now traditional ball and socket type joint. Given the design and materials of the late 1960s, this rubber bushing was probably not too bad when it was brand new, but over time it wears down, and you lose a lot of steering feel and directness with this nasty old rubber. Again, every air-cooled Porsche used this tie rod style for two decades. That is, every air-cooled Porsche except one.

Then The Porche 930 Happened

It was in 1976, Porsche introduced the 911 Carrera Turbo (type 930) with a 3-liter engine and a turbocharger providing additional shove. It was a phenomenal car, a world-beating car even, an insanely fast car in its day. Because the Turbo was a bit of a handful to drive, Porsche wanted to make sure there was not any steering bind or even momentary delay in the response of the front wheels to the driver’s steering inputs. As a result, they removed the standard tie rod and replaced it with a metal-on-metal ball and socket-type joint at the steering rack.

Since then, Porsche enthusiasts have figured out that the two styles of tie rods are interchangeable and have installed several thousand sets of Turbo Tie Rods on non-turbo Porsches. Which is exactly what we do here. The kit shown below is the Porsche 930 kit, which we retrofit to the early 911s, 912, and 914 we care for.

Next Steps – Proper Alignment
After the tie rod update, a proper four-wheel tracking alignment must be carried out.
Our workshop uses the Mercedes Benz of alignment machines, the Hunter Hawkeye Elite, recommended by most of the major European auto manufacturers.
There are four key measures to each alignment: caster, camber, toe, and thrust angle, and we’ll explain those below.

This suspension angle shows how the tire angles away from 0 degrees vertical when viewed from either the front or rear of the vehicle. Expressed in degrees, negative camber means the top of the tire tilts toward the vehicle’s center, while positive camber means the top tilts away from the center. A visual cue for a camber problem is excessive tire wear on the inner or outermost ribs.

This angle shows the forward or backward slope of a line drawn through the upper and lower steering pivot points when viewed directly from the side of the vehicle. Also expressed in degrees, caster is measured by comparing a line running through the steering system’s upper and lower pivot points (usually the upper and lower ball joints of an A-arm or wishbone suspension design or the lower ball joint and the strut tower mount of a McPherson strut design) to a line drawn perpendicular to the ground. Caster is said to be positive if the line slopes toward the vehicle’s rear at the top, and negative if the line slopes toward the front. A visual cue for a caster problem is serious tire scrub laterally across the tread face.

Identifies the direction in which tires are pointed relative to the vehicle’s centerline when viewed from above. Toe can be expressed in either degrees or fractions of an inch. When looking down upon a vehicle, “toe-in” is when the leading edge of the tire is pointed toward the vehicle’s centerline. Conversely, “toe-out” refers to a tire face that points away from the vehicle centerline. The toe setting is typically used to help compensate for the suspension bushings’ compliance to enhance tire wear. Service Tip – The toe alignment also can be used to adjust vehicle handling; for vehicles that “wander,” the toe can be set slightly more toed in for directional stability. 

Thrust Angle
Consider an imaginary line drawn perpendicular to the rear axle’s centerline. This measure, expressed in degrees, compares the direction in which the rear axle is aimed at the vehicle’s centerline. The thrust angle also confirms if the rear axle is parallel to its front axle and that the wheelbase on both sides of the vehicle is the same. If the thrust angle is incorrect on a vehicle with a solid rear axle, it often requires a trip to the frame straightening shop to correctly reposition the rear axle.

Tech Note
There are various reasons for any of these alignment measures to be incorrect. At the same time, adjustment angles can be adjusted by a skilled technician to correct for inherent vehicle problems, correct for unusual tire wear, or to improve the performance and feel of a vehicle.

Alignment Specifications
All vehicle manufacturers have set specific alignment specifications for each vehicle. These are the “preferred” angles for camber, caster, and toe (with the preferred thrust angle always being 0 degrees). OEMs also provide the acceptable “minimum” and “maximum” angles for each specification and are usually within plus or minus one degree of the preferred angle.

Vehicles With Steering Angle Sensor
Sometimes, an additional labor operation must be performed to calibrate the steering angle sensor. The Steering Angle Sensor is what tells the onboard system if the steering wheel is pointing straight, left, or right and by how many degrees. Suppose the steering angle sensor data does not match with the rest of the vehicle data. In that case, the traction control system will likely trigger a plausibility error because the car doesn’t match what the steering angle sensor tells it. As mentioned, this is a separate labor operation from a standard four-wheel alignment and will be billed separately.

How We Can Help You
The Service Team here at Atlantic Motorcar is well experienced in this issue and others; with over 35 years of European auto specialization, serving clients from the areas of New England, we are familiar with the needs of the special service of your auto.

As Maine’s leading European auto specialists, we provide expert-quality services at a fair rate than nearby dealerships and specialty shops. If you’re experiencing any of the above-mentioned symptoms in your auto, please call us immediately; we can usually see your car the same day! At Atlantic Motorcar, we’ve developed some very specific procedures and tooling, combined with our expert technicians, to make this otherwise onerous repair a snap.

Questions or if we can help with service on your Audi, BMW, Mercedes, Sprinter, Honda, Infiniti, Lexus, Mini Cooper, Porsche, Volvo, and VW, please contact us. Our team of Service Specialists is here to help, for even the newest autos! (207) 882-9969.

Knowing, not just “doing,” that’s the Atlantic Motorcar Center way.

The Atlantic Motorcar Center Service Team

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