EPS Control Arm upgrade - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Any opinions on this control arm concept? This seems to be a weak point in the stock suspension. Frustrating when you've gone through all time/expense and the part doesn't hold up.

It makes sense to me I think I will look into it further. Do you have any idea what they are selling for?

What would be the downside? Stiffer ride maybe?

This is a very complicated technical argument. Degrees of freedom are important in mechanical systems. The spherical bearing eliminates force coupling (due to the spherical design being unable to counter moments) and is lighter, versus the beefier replacement which appears to be cylindrical, couples forces, and acts as a spring. Which is "better?". The devil is in the details. Bigger / resisting force is not necessarily better. This gets into the nit picky engineering details of the suspension design and strikes to why a spherical (and relatively expensive / complex) design was chosen here instead of a simpler cylindrical design. Ride comfort perhaps? In a box? Perhaps. I really don't know. I'm sure there are folks involved with racing that can clarify.

These EPS control arms can be bought @ < ****************************************.com > and < www.design911.com > in England for ~90 UK pounds. I've used both Design 911 and EPS suspension parts with good results - made in (I think) Czechoslovakia. Note that these control arms only fit the front suspension of the Boxster, not the rear. EPS also manufacture the roller bearing IMS retrofit, the subject of another (heated) thread, but I better not mention that......

^ front only? That seems like it would produce a mixed result. Stiff front end and possibly more heavy lifting by the rear that is already a weak point.

The real question is are you looking to soften your steering feel and ride or get a more precise steering. His opinions are wrong and flawed. The bushing will soften ride and decrease steering precision. Why has Tarett, RSS, and Elephant all removed bushings from their control arms and links. Why have they gone to billet ball bushing. To increase tightness in suspension and steering. Bushing compress, and any compression changes the wheel geometry changing steering characteristics chamber and tow. His video is base on opinion and not any mechanical theory , and his opinion is mostly wrong. The Ball rides in the radial cup and when it is contained in a rigid bore and compressed as designed from both end, the surface area is larger due to being a radius. Once the end compression is remove and the radial bushing is out of the bore the appearance is that the pressure is only on a narrow linear band in the center. This is wrong and only happen if the bushing is worn out. Second opinion that is wrong. As it is swiveling somehow there is a reduction of contact area and or performance. The ball and radial bushing are designed to operate at an angle, and has no need to return or be maintained in any location. As a design it maintains the same rigidity and force per square inch no matter what angle it is operated, within the design arc. So if the design arc is +- 10 degrees everywhere within that 20 Degrees the contact surface remains the same and force is dissipated the same. His third opinion that is wrong. As the angle of operation on the straight bushing is moved from perpendicular the surface area is maintained. In reality a portion of the bushing is placed under traction and a portion under compression. So as the arm is raised off perpendicular the top half the bushing become loaded. The lower front side is unloaded, and the lower rear side goes under traction. This reverse as the arm is lowered. In reality this causing premature wear and a lack of rigidity. The rigid ball joint with the Teflon bushing is more solid and although it can be prone to eventual looseness due to wear on the contact area, the contact area is on a radius which is manufactured to match the surface of the ball. The surface area of a radius is longer than a flat bushing. So in reality it reduce the force per square inch and therefore can be loaded more without flex, since the force is exerted over a larger surface area. Second positive point is the rigid ball bushing while not allowing lateral motion, also prevent components of axial movement as well. Hat style urethane bushing allow a slight flex both ways softening the feel of the road. Compression of even a few Thousands of an inch changes the tire contact patch (Chamber) and angles (Tow). Urethane flat bushing compress immediately as force is added. The higher the force the more the bushing can flex. Which is really good if you would like a softer road feel. If precise steering is what you crave, your better off getting a more solid ball bushing with a more durable cup.

Not trying to hi jack this thread but, What are your thoughts on these? PORSCHE 986 987 BOXSTER & BOXSTER S 97-12 ADJUSTABLE FRONT TENSION RODS #6435 - Top Speed Auto Accessories, Inc.

Its all compromises, with the factory style it will hold alignment better and be more precise, at the cost of durability. With the urethane it may be more durable and quiet, at the cost of precision.

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This is more like factory but no mention as to whether the rod end is plastic encased, all metal, or otherwise. But with this design it will most likely wear as fast or faster than the factory style. Plus side is if you can source the rod end it can be easily replaced. It does look heavier than stock though. more unsprung weight

Quotes source post: 443340

I run the same manufacturers on the rear. The ball link on the rear is a sealed steel uni-ball link.