worf928

Given the opportunity and desire to refresh a 928 and to get back as-much-as-possible the 'new car feel' how important are the giant blocks of rubber on top of the coilovers?

I would think that they are very important to the proper cushoning and isolation of vibration. And I think that after 20 to 30 years of exposure that their material properties would have degraded.

How long should we expect them to last? What are signs that they need to be replaced? Has anyone ever replaced them? And if so, what was the effect?


928 343 047 08 for the front



928 333 043 01 and 928 333 465 01 for the rear.



Thoughts? Opinions? Evidence? Anecdotes?

Mrmerlin

I have inspected them but never replaced any,
they are in a protected area and away from sunlight.
I would venture a guess that you would never know the difference between driving a car with old shock towers VS new

worf928

Same here. I've never found any that were "hard." I have seen a bit of dry-rot cracking but nothing bad.

True. But they are exposed to oxygen and heat cycling neither of which are 'friends' to rubber.

This is the $1100+ question.

GregBBRD

The rears are farther away from the heat and get so bad that it is impossible to not have the rear end clunk with any new shock absorber.

While I used to replace these on a regular basis, the last time I tried to get some, they were NLA.

I've never replaced any front ones.

Tony

i guess one would think that replacing them should make a difference.? I mean they are old..and whatever the formula of the rubber is, it is going to suffer over time.

Is there a thread out there with a list of "rubber" suspension related components? It would be nice to do it all at once if one could.

Tom in Austin

I changed mine when I put in new rears, and held on to the old ones in case somebody wanted them someday. They look like new, no outward signs of any wear.

Now that they're NLA if anyone's looking for a pair of these, I'll offer the pair for $45 delivered in the 48-states.

Michael Benno

When I replaced my suspension this summer I ordered all those rubber bits aticipating they would be worn, hard, and cracked.

All the parts were and still are available:

928 333 043 01 $75
928 333 465 01 $31
928 343 047 08 $268.

I ended up returning all three of these items as all of my existing parts were in perfect condition.

worf928

Yeah, they are all now (still or possibly again) available.


How many miles on your S4? And did it spend a lot of time outside? Or was it mostly-garaged and protected from freeze-thaw cycles?

worf928

Any discernible change in ride?

Michael Benno

My S4 has 142K miles on it and it was a NorCal/Oregon/Washington car. The interior is in fairly good condition and doesn't look like it spent much time out in the sun.

The rubber was in such good condition that I assumed it was replaced at sometime before but I could not find any reference in my repair history.

The car rides fantastic now and all I changed was the struts and arm bushings.

Adk46

I’m very interested in this thread. I’ve noted the frequent “replace all the rubber bits” advice given on this forum, but have also noted that many big suspension bits of rubber are not often replaced. It’s difficult to judge the current NVH of a 30-year-old car against what it might have been new.

Oops, jargon: NVH = noise vibration harshness.

Michael Benno

Here is what my bushings looked like when I pulled them, before I did any cleaning. notice the clean copper grease looks fresh. I think it's pretty easy to evaluate what deteriorated rubber looks like. It's hard, its cracked, it's wrinkled and will rub off in crumbs if old.

chart928s4

FWIW mine were in even better shape than Michael's. They looked virtually new once I cleaned off the old grease. But I would like to know the ride effect if any also.

worf928

Difficult but not impossible. Over the years I've had the opportunity to test drive several 'kept-in-a-bottle' 928s. There is a big difference in NVH between these examples and the run-of-the-mill 928 that's been exposed to 'normality' for 20-30 years.

Figuring out the marginal utility in NVH reduction for replacing any particular aged part is difficult. Hence this thread.

Mrmerlin

Dave for others reading this some notes on what I have found,

the parts that I do replace on every shock now are the white washer and the piston shock bumper.

NOTE every shock set I order also includes these as most are partially destroyed if not totally gone.

The new Black Boges have white washers included with them, but ask when placing the order.

NOTE Its also prudent to inspect the plastic dust boots on the shocks before ordering,
as its common to find them also cracked or ready for replacement mostly the front boots.

NOTE the new shocks that are being produced are made with thinner piston rods,
this goes for Boge and Bilstien so the shock bumpers that would be a friction fit on the originals now sit on the white washer.
The mounting area diameter for the strut towers is still the same size.

NOTE before the car gets jacked up for chassis inspection take a ride height measurement.