So my 86.5 928S has a habit of bottoming out on hard right turns if there is a bump or incline in the way, and going bang when hitting uneven surfaces. Unless I leave a driveway very slowly I will hear the front spoiler gently scraping against the pavement.

1) Is this normal? Maybe it is on a lower car like the 928S
2) Do I need new shocks? Maybe.
3) What kind of a shop can switch shocks on a 928S?
Can this be done by:
Local auto parts place (NTB)
Local mechanic
Porsche mechanic
Only Mr. Merlin level people

I'm going to be taking the 928S out of daily driver service for awhile now that I have the 944S repaired, so I have some time to work on things.

 

Until you measure the ride heights and tell us those, it's pretty tough to tell you much.

 

Seems your front end is sitting too low and you need to investigate why. As GB says ride height data really needed.

You may have a broken spring, the car may be setup incorrectly, with age the springs sag and seemingly the front more than the rear etc etc.

Needless to say when the front end is too low your a/c compressor, your alternator and your engine are under threat of mechanical damage. Bash plates highly recommended especially on examples that sit lower than stock whether by design or neglect.

 

Link below.

 

What GB and Fred said, check the ride height vs factory settings. My car was very low when purchased and I needed to be very careful with curbs, driveways, speed bumps. It looked cool (front down rear high), but was very annoying to drive (my avatar pic is a"before" new shocks picture). It was sitting way below factory height due to sagging springs and bad shocks (both original to my 1988). Replaced the springs and shocks all the way around, and I installed bash plates for cheap insurance (you can't see them unless you are under the car). Now the ride is better and it handles better. I'm still paranoid about speed bumps/driveways cause its still a very low slung car, but its a non issue now. My local indie did the work (ex Porsche/Rolls Royce wrench). He installed OEM springs and shocks (I think Boges). The front end looked really high when I got the car back from the shop, but after a few days of driving the front suspension settled to the correct height.
Brian

 

The biggest problem we are running into, almost on a daily basis, are lower control arms with the front rubber bushing de-attaching from either the control arm or the aluminum outer shell. It is literally everything Mary can do to keep enough of these items (we use rebuilt arms from 928 International) in our inventory. We might install 4-5 sets in one week!

These bushings are a huge percentage of the front spring rate.....something that all the 928 "gurus" and most dedicated "track" guys fail to recognize. When one installs a new arm, a full size human can barely deflect the arm....up or down.

SERIOUS percentage of the spring rate!

And if anyone tells you to remove the stock bushings and install a poly bushing (without a serious change in the front spring rate) they are absolutely complete idiots....just ignore them.

New shocks, ride height, corner balance, alignment.....is like taking money and tossing it up into the wind, if the lower control arms have bad bushings.

First step: Visually check the front and rear bushings. If there are any chunks missing, they are junk. If the driver's side is swollen from the leaking power steering fluid, they are junk. If they look intact and pass all the visual tests, you can remove the front tie downs and pry down on the arms. If the front bushing rotates by hand, they are junk.

And......don't be stupid. You can't just replace one. Since they are a major part of the spring rate, they must be replaced in matched pairs to get the same spring rate from one side of the car to the other.

 

Ok, very helpful. I'll measure the distance tonight or tomorrow evening depending, I'll also take a picture under there for good measure. I believe I do have a pair of crash skids, if they are mounted right in front of the suspension mount and look like two half shells then that's what has been hitting. From what I could see there was no impact marks against the alternator bracket, AC compressor bracket or the oil pan (all of which would be bad) The skids do show impacts.

 

Well, getting under there on the driveway is a bitch on wheels. Also my driveway is sloped, but I did the measurements perpindicular with the ground so there is that.

Both sides read about 5.5 inches which is 130mm. So it's about 50mm low, or about an inch and a half.




The bushings did not look oil soaked, but I'd have to put it on the ramps to get a really good look.




I assume there is a special Porsche certified tool to check the ride height. I should also check my tire pressure, but I doubt that could lift it 50mm.

This is what I think is hitting. The alternator and other items down there appear ok.

 

Could you use something as simple as a paint stir stick or something? Cut it in half and but one piece against the proper measure location and set the other half on the ground and by-pass them, put a pencil mark across both pieces remove them and get your measurement.

 

I took a piece of aluminium welding rod, you could use a metal hanger, and cut sections at 2 mm increments, not unlike a feeler gauge.
Works well, I add 1mm if it's in the middle.

 

That's absurdly low. The shock bump stops are hitting and there is so little shock travel that the brand/condition of the shocks is moot.....they are barely moving. All of the rubber in the control arms will have twisted so far that as soon as it is raised, the rubber bushings will quickly break.

I won't lower a street car below 150 mm, without some serious customer face to my face conversation, which starts with: "You need to tell me, in detail, why you need the car to be this low and why you want it to drive as badly as it will."

BTW, the bump steer becomes so absurd, tie rods must be modified, after about 160 mm. By 130 mm, wherever you set the front toe doesn't even matter.

 

Greg does not need my endorsement, but that is in fact extremely low. My car was at 140 and dragged on any driveway. It hasn't scraped anything since I brought it up to factory height (~175mm)

Tip 1: Make sure you are measuring to the designated flat machined measuring spot front and rear.

Tip 2: People have all kinds of tools to measure the height. For example, Rob Edwards has a set of straws cut to several lengths. I just used a telescoping magnet pickup tool - worked great and already had it in the toolchest.

 

I'll try a better tool, but it did seem consistent from side to side and it's *low*. How can I raise it back up?

C

 

I did something similar with wood BBQ meat skewers and then taped little post-it-note flags on each one with its measurement.

 

Search is your friend. There are lots of threads describing the process. Short version: There are threaded aluminum sleeves on the shocks. The large nut threaded on the sleeve supports the lower part of the spring. With a C spanner, turn the nut so it moves upward. It is wicked annoying but low tech and doable by anyone.