worf928

For the record, I no longer settle 928 suspensions with under 20-mph operation over a very short distance (which was far less than 2 miles, more like 800 yards.) I found that the method does not reliably cause all 928s to settle after my roads around here were repaved. I have a more reliable method that doesn't require a 928 to move under its own power or even more than a few feet.

Somewhere between
- it is safe to drive from the work bay to the alignment rack with the rear lower control arm bolts backed-off two turns
and:
- it is unsafe to drive on a highway at 55 mph with the rear lower control arm bolts backed-off two turns
exists fundamental truth in the form of a fuzzy gray line.

The factory pull down method for settling the suspension only works on slip plates.

Most folks don't have an alignment rack with slips plates.

So, I guess the only way to be safe is to have your 928 flat-bedded to an alignment shop, hand them printouts of the ride height specs, pull down procedure, torque specs for the LCA bolts, and alignment specs and then go sit in the waiting room.

It logically follows that it is clearly impossible to assemble the 928's rear suspension correctly under any circumstances: Since nothing can be preloaded before applying final torque no method exists to assemble the rear suspension in such a way that the various joints are fastened in their settled positions.

FredR

Eric,

You make statements inferring that if anybody does something different to what you perceive to be acceptable then by definition they do not know what they are doing. That some of us have the ability to fathom out what is safe and what is not may well be beyond your comprehension but that is exactly how some of us operate. The entire point of this list is to share knowledge and debate the relative merits.

The WSM procedure is what it is -quite clear and intended to be done by pull down procedure no need to debate that. I fathomed that out some 16 years ago when I started playing around with enhanced alignment settings. Unfortunately there was no capability here to follow the procedure so I came up with my own approach which pretty much aligns with what Dave is saying [great minds really do think alike]. I also bounced it around my more knowledgeable 928 friends and to a man they agreed with what I was intending to do.

Some folks tighten the thing with the car up in the air then wonder why it takes forever to settle- durrgh! The front bearing is tightened as normal, The torque value for the rear bearing is 88ft lbs the front bearing is 50 ft lbs- ever wondered why they are different? Fact is most of the loads on the rear bearing are absorbed within the captive semi circle and as long as the bearing cap is in position it will absorb all the forces imposed on it irrespective of whether the cap is at full torque or partial torque and if one were daft enough to jump the car into the air it would take no more than finger tightness to hold it in position.

It was my assessment that most of the torque on the rear bush bolts is required to compress the rubber such that it cannot rotate within the bearing cap. The shear load is taken by the bearing geometry and the spigots the cap locks into. Thus if rotation of the rubber within the bearing is not a problem then it takes very little in the way of bolt stress to hold everything in place. So to allow the thing to "Settle" I fasten the bolts with my socket set wrench and a 19mm 1/2 inch socket. With the short radius arm and me lying on the floor trying to reach the bolts I reckon I can only get about 25 ft lbs with the thing. That is not going to hold the rubber static and more to the point it is not going to come loose. First time I did it I was somewhat nervy and checked it frequently but the reality is there was nothing working to loosen it.

Would Porsche ever tell you to do this? - not a chance. On the other hand nowhere do they tell you not to drive the car in anything less than fully torqued spec. Bottom line - find a place who can do the job lot and be done with it or take responsibility and approach it this way. I limit my speeds to around 50 mph max, no limit on brake force and no limit on cornering. I take speed bumps sensibly and I know the roads I am driving on do not have any potholes- thus I take responsibility for my actions and am secure in the knowledge that I have done this many times over- tried and tested.

On the other hand if you have never done so then you have no basis to know whether it works [or not] or whether there is any real world danger involved in doing so and for sure I would not want to rely on the average chap who turns spanners to make such an assessment- all he needs to know is the procedure and to follow it.

Whether folks agree with this approach means little to me. One of, if not the most important passive safety feature on the entire car is arguably the neutral scrub radius on the front geometry - I make a big deal about following this- you disagree with me. Nothing wrong with this- only one of us can be right though.

dr bob

You guys will of course laugh at my compromise procedure. Full torque when the car is on the floor after the work. Go drive and settle the suspension. Loosen the clamps with the car still on the floor. Tighten the clamps with the car still on the floor.

When you loosen the clamp bolts, the inner end of the control arm wants to go down with the clamp. Bounce on the car a little to relieve any remaining twist in the bushing. Torque to spec. Two full turns on the bolts is plenty to loosen to let things relieve themselves. I could probably find a way to push up just a little on the inner end of the control arm, and have the bushing completely free.

GregBBRD

I leave everything that pivots on a rubber bushing loose and pull down both ends of the car, before tightening. Sway bar drop links (especially important on the rear), shock mounting rubbers, rear upper dog bones. Literally everything. The difference in how the cars "feel" is amazing, when the rubber bushings are not preloaded in one direction, but in a neutral position at rest. Make sure that the fuel tank is, at least, 3/4 full.

David is correct, you really need slip plates to do this (which you can make from some light weight sheet metal and some grease between two of the sheet metal pieces.
....An $80,000 Hunter alignment rack is a handy tool, too.
I'm not sure how I ever "lived" without one, while I'm not sure how I'll ever use it enough to pay for it!
Typical tool dilemma.

worf928

I assume the sarcasm of the second half of my post was not lost.

I also tighten all of the pivot points in their neutral positions. Of course, one must do this with load on the suspension.

Yup. This --^ is what I do. I have eight pieces. Four for each wheel. Each set has two 3/16" holes drilled through to accept a pin to keep the wheels from 'spitting' out the top plate when rolling on to them. The top two, for the front wheels, feature rounded corners.

A level floor is required. Don't attempt on a four post lift or alignment rack...

FredR

Bob,

It is not a question of "laughing" but a "wry smile" might be appropriate.

The notion that unbolting the rear cap relieves spring tension in the rubber simply does not hold to my way of thinking. I dare say it holds to a small extent but nothing of relevance is how I view it. Springs have a memory and they try to set themselves around that memory. The problem with rubber is that the memory "changes" with unrestrained load. So, we jack the car up, remove chassis weight from the system and the springs expand to full extension. The stresses redistribute within the body of the rubber and that becomes the new memory position. We finish the job, deck the car but the new "revised memory" is fighting this and will continue to do so thus why it does not return to the previous height.

My perception is that to recover the previous memory the system has to be worked and thus the pull down procedure and why it has to be done with the cap removed. This way the memory will reset far quicker when the compressive load is applied. My approach is following what the WSM says but taking a different route path. That it is counter intuitive is what it is and why as a point of principle I advised what I do as a point of information- beyond that it is up to the individual owner to decide whether he wants to do the same or not- thus the post script of your signature line! Try doing this with the cap in full tension and it is no wonder it takes a long time.

Now, to be clear, the only time I adopt the procedure with the rear caps not fully tensioned is when I have a need to go to the alignment shop and do not want to drive around for a several hours as has been the case a few times. Just driving from home to the shop in this fashion is about enough to achieve the task. All that being said where this really matters is when new or refurbished arms are installed. When the bolts are tightened the rubber takes a permanent set and I reckon it is critical such set be taken with the arm in the settled position. I have yet to attempt such but I can see this in my near future. This makes me think it may be best to fit the arm without the coilover, jack the arm into the horizontal position and then tighten the bracket. This assumes that as in my situation, there is no prospect of following the WSM procedure.

It is quite a conundrum and it seems to get even worse if one is rebuilding the entire suspension system. Avoiding pre-loading of the front and rear drop links must be nigh on impossible with the stock setup. One would think that when they went to adjustable coilovers they should also have modified the drop links to be adjustable. Thus why if one is going to lower the car some I reckon that Louie's rear links and the Devek bar are important because one can do such with these items. So, in summary, the rear lower arm, the front lower and front upper arms can be set in situ as can the front and rear drop links with the aftermarket kit. As for the upper rear dog bones nothing I can do about that but I reckon they are not that critical.