8 cylinder front engine iconic vehicle
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By worf
#66223
Front coilover mounts ("concave washer" 928 343 047 08)

Left: '90 130k miles. Right: new

Old one's "smooshed" by about 5mm.

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By worf
#66426
maddog2020 wrote: Sat Mar 13, 2021 8:49 pm you gotta give Porsche credit. they may collapse but how many fail? even at the track. these things are built like tanks. Most of these cars are 30-40 years old now. Most of them are older than their owners.
Yup. Lot's of other cars need shock/strut mounts replaced frequently. The 928's just see to soldier on forever.
maddog2020 wrote: Sun Mar 14, 2021 5:41 pm @ nearly $500 per side...... lots of people may wait until they are cracking. I bet replacing them probably improves the ride quite a bit.
We shall see. But, not any time real soon. This one's still got a long way to go before first drive.
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By worf
#66530
Crumpler wrote: Mon Mar 15, 2021 11:01 am Besides the 928 Motorsports rigmarole.
The ones that are a solid hunk of aluminum? Those ones?

So... yaw’ll know that on the 991/981/718 the struts (not coilovers) mount metal to metal with the chassis? And that the chassis tower mounts have a tendency to break off from the rest of the inner fender when used in ‘racing conditions’ (or even sometimes from hitting a really deep pothole?)

When the wheel hub goes up and down the coilover (or Mac Strut on the new ones) bottom moves up and down. I’m not talking about the axis of shock push rod travel. The angle of the coilover with respect to the top changes: it flexes at the chassis mount. It’s a simple trig problem to calculate the angle change.

Anyway: I would never, ever want a metal-to-metal mount for the chassis and coilover on a 928. You need something that will flex between the coilover and chassis tower mount or... bang!
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By maddog2020
#66599
and the older the mount the stiffer they get. I'm going to bet the steering feels much smoother when going over bumps. I may have to order a set because I've replaced everything else... can't have one old part canceling out all the new ones. besides I'm still waiting on my spindles....
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By worf
#66606
GT4:
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By worf
#66629
FlatSix wrote: Mon Mar 15, 2021 8:52 pm WTF????

Are they pulling an Alfa and buying surplus Soviet steel?
As you can imagine, there is a lot of debate. Failures seem to be rare but still enough that it's a "thing." Not RMS or IMS level. Yet.

From reading some (certainly not all) of the long threads on this failure mode on the various boards, my *personal* opinion is that the failure is linked to folks that lower the ride height and/or more common for cars that come from the factory with low ride height (e.g. GT4, cars with SPASM, folks that slam their P-cars to the ground with lowering springs.) So, you get more chance of completely compressing the strut on a big hit AND the slight change in initial control arm geometry doubles the angle change of the strut relative to the mount when the wheel and hub assembly has to "rise" into the wheel well. So: significantly more bending stress on the chassis tower mount.

The ClubSport GT4s have an extra tie bar that ties the top of the strut to the fire wall so that when(!?) the failure occurs on the track the car is still controllable. AND there's a Porsche Motorsport part and procedure for replacing the mount in the inner chassis.
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By maddog2020
#66630
worf wrote: Sat Mar 13, 2021 8:36 pm Front coilover mounts ("concave washer" 928 343 047 08)

Left: '90 130k miles. Right: new

Old one's "smooshed" by about 5mm.

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Can you get a more accurate measurement since your ruler is not lined up? my 928 has spent most of its life on jackstands... so I wanted to measure how bad off they are... they are still 31 years old
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By worf
#66631
maddog2020 wrote: Mon Mar 15, 2021 5:21 pm I may have to order a set because I've replaced everything else... can't have one old part canceling out all the new ones.
That ended up being the 'theory' on this resto. With Mark's Weissach pivot bushing replacements available and a set for this one already installed, those front tops were the only original piece of rubber left.
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By worf
#66632
maddog2020 wrote: Mon Mar 15, 2021 9:16 pm Can you get a more accurate measurement since your ruler is not lined up? my 928 has spent most of its life on jackstands... so I wanted to measure how bad off they are... they are still 31 years old
That was to be a comparative measurement. But, yeah, I was thinking yesterday that I should measure both more accurately so that I can take measurements of 928s that roll into the shop.

So, I'll do that. Tomorrow.
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By maddog2020
#66635
it would be interesting to see a cross section if you care to cut one in half. In looking at the profile I'm wondering if the new ones were made differently some aspects look really out of proportion, and while shrinkage might be part of it, It wouldn't be the 1st time Porsche changed the "formula" for new parts. Not to mention the average 928 home mechanic probably has better measuring tools than Porsche did back when these were designed.
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By worf
#66643
maddog2020 wrote: Mon Mar 15, 2021 9:37 pm it would be interesting to see a cross section if you care to cut one in half.
I plan to cut an old one up. Not real soon. But, I ain't cuttin' a new one up 'less you send me one :nono:

maddog2020 wrote: Mon Mar 15, 2021 9:37 pm In looking at the profile I'm wondering if the new ones were made differently some aspects look really out of proportion,
What do you see that seems out of proportion? I stared at them for a few minutes. The studs in the new seem different.

maddog2020 wrote: Mon Mar 15, 2021 9:37 pm and while shrinkage might be part of it, It wouldn't be the 1st time Porsche changed the "formula" for new parts.
These came from Germany. Based upon discoloration and deterioration of the bag, dust, and the number of stickers, I'm betting on NOS.

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By worf
#67085
Bag with stickers is long gone.

Old smooshed mount is 74mm at the point where the spring terminates. This is the easiest place to measure with the mount installed.

New mount is 5-6mm taller.
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By worf
#67091
maddog2020 wrote: Wed Mar 17, 2021 10:11 pm between this collapsing and springs aging this might be why some cars are on the bottom of the adjustment threads trying to get cars level. great find~!
'tis an easy measurement to do. Can do it with everything installed. I did it, but couldn't take a picture of me doing it.

So, we could gather data from the fleet: model year, mileage, top mount height...

Get enough data points and we might get an age/mileage/height surface plot.
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By checkmate1996
#67203
I just happen to be doing my shocks after finding out one of my front konis was hosed. This is very timely information. Thanks for sharing...
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By checkmate1996
#67415
1985 - 97000 miles - Sat for a long 15 years - Driver 71.63mm Passenger 74.44mm. Worse than your measurements but no budget to replace at this time so I have to go with it. Overall, they LOOK ok but clearly that's all they got going for them... :bigcry: :cussing:
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By worf
#67420
checkmate1996 wrote: Fri Mar 19, 2021 3:20 pm 1985 - 97000 miles - Sat for a long 15 years - Driver 71.63mm Passenger 74.44mm. Worse than your measurements but no budget to replace at this time so I have to go with it. Overall, they LOOK ok but clearly that's all they got going for them... :bigcry: :cussing:
Don’t :bigcry: over it just yet. What we don’t know is how much new mounts settle in the first bit.

But, of course, we do suspect that new rubber is ‘more-rubbery’ that 30- to 40-year-old rubber.
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By The Fat Man
#67555
Sheet.
One more thing to worry about selling a kidney to replace when I take the front shocks apart. Again.
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By Gary Knox
#89150
Anyone installed the new ones and driven the car at least a short distance to see how much the new upper mounts compress?

By the way, Delaware Porsche has them on their web site for ~$270 each. https://www.delawareporscheparts.com/oe ... dhcw%3D%3D
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By worf
#89178
Gary Knox wrote: Fri Jul 02, 2021 9:54 am By the way, Delaware Porsche has them on their web site for ~$270 each.
Yeah, that’s about what one should expect. The rear mounts are/were cheaper IIRC.

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