[Zirconocene]

Has anyone ever cut one of these in half to see the gooey insides?

How much technology is going on with these? If I stare at PET, it sure looks like there is some amount of carrying load put through into this part. Is it really dependent on the bonded rubber to manage the stresses from the shock load? Are there known cases of the rubber just breaking away and putting all of the load from the front suspension on the spring? Does the bump stop do some of the work here, at other than full compression (don't see how, but...)?

I'm just trying to understand why these parts are so expensive, separate from scarcity (which, I don't know, maybe) and Porsche tax. As a counterexample, parts for modern Mustangs look to have a bit more engineering going on for the analogous part, so I'm really trying to learn what's going on.

Thanks for any insight or pictures.

Cheers

[worf]

Has anyone ever cut one of these in half to see the gooey insides?

I have not. Not that curious so far. I have replaced them on several 928s that were getting the "full monty" suspension treatment.

There are pictures of new and old mounts on this forum:

Front Coilover Mounts - Or, that's where my ride height went!

How much technology is going on with these?

None as far as I know. They're just hunks of bonded rubber and steel I think.

If I stare at PET, it sure looks like there is some amount of carrying load put through into this part.

Well, they get roughly 1/4 of the total weight of the car through compression loading. Add some dynamic compression loading from movement.

They get a tiny bit of bending force from suspension movement. But, very little due to the double-A-arm design; unlike Macpherson Strut suspensions for all other Porsches.

Is it really dependent on the bonded rubber to manage the stresses from the shock load?

I would appear so. Someone can slice one in half to see for sure.

Are there known cases of the rubber just breaking away and putting all of the load from the front suspension on the spring?

I am aware of exactly zero.

Does the bump stop do some of the work here, at other than full compression (don't see how, but...)?

No.

I'm just trying to understand why these parts are so expensive, separate from scarcity (which, I don't know, maybe) and Porsche tax. As a counterexample, parts for modern Mustangs look to have a bit more engineering going on for the analogous part, so I'm really trying to learn what's going on.

I assume that they are so expensive because NOS is depleted and PAG has transferred the part to their Porsche Classic Division.

As a counterexample, parts for modern Mustangs look to have a bit more engineering going on for the analogous part, so I'm really trying to learn what's going on.

Do "modern Mustangs" use a double-wishbone front end with true coil-overs? Or do they use a Macpherson Strut design? There is a huge difference between the two since in a Mac Strut design the strut is also camber control and therefor can't have rubber at the top.

[N_Jay]

. . . .
I'm just trying to understand why these parts are so expensive, separate from scarcity (which, I don't know, maybe) and Porsche tax. As a counterexample, parts for modern Mustangs look to have a bit more engineering going on for the analogous part, so I'm really trying to learn what's going on.

. . . .

I am sure part is "Porsche Tax" but a lot of the cost of any small part is related to the quantity produced.

I am sure "Mustang" parts are produced in the hundreds of thousands and 928 parts in the hundreds to thousands.

[Zirconocene]

Excellent reply, thank you.

Also, point taken about modern Mustangs and the differences between the double A arm and McPherson types but I think that also sort of reinforces the point, McPherson suspensions require a little bit more from the top mount, engineering-wise. Maybe, I have to think about it some more.

Anyway, I've been thinking about this because I've been wondering how one might go about making a rebuildable part for the 928. I know that there are parts available now but I'm paranoid about the future, and have no faith in Porsche Classis's ability to keep costs reasonable for such small, small volume parts. Plus, I just like thinking about these things.

Cheers

[h2pmr]

i have a spare one, will cut it in half and take some pictures, give me a couple of days.
cheers
Phil

[h2pmr]

as Dave says its just bonded solid rubber with a steel plate in the middle
cheers
Phil

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[Zirconocene]

@h2pmr : That is awesome, thank you!