Strut mounts...do they compress over time?

[Scubaboo]

Here is a pic of a strut assembly for a 2010 Outback that shows the strut mount installed on it.

 

Does the lower part of the mount, which is also the upper spring perch, compress upwards over time?

 

[Scubaboo]

Here is the exact same model of shock mount as in the OP, here installed on a Forester.  It's well used and *looks* substaintially lower.  It could be the angle though?

[silverton]

It's rubber so probably.

[Scubaboo]

^That's what I was thinking?  I'm not sure if the spring perch is part of the rubber-suspended area or not.

[DrD123]

The spring seat (rubber part that sits inside the "cup" part of the upper mount) will creep a little, but as it creeps the additional "space" is taken up by the spring (the spring is always under compression when the strut is assembled) - if you take apart a rear strut assembly, the rubber seat will have a permanent impression of the spring in it, whereas the new one doesn't (it compresses when the spring is installed, and eventually takes on a permanent set in that position)

the upper mount is more or less all metal as far as the vertical part goes (with the exception of the seat - the seat is part 20375 in the diagram) - the distance to measure (to see if there is a change) is the face the spring mounts/presses against and the mounting surface of the strut (where it mounts to the frame) or the point where the strut shaft bottoms out on the mount - the cup part is likely going to be a little different when comparing parts from different manufacturers.

[Scubaboo]

Well, just confirmed they do.

I went out and got a new mount and compared it with the old.

[DrD123]

that's interesting - I didn't realize that the middle part was rubber (I remember drilling out the rear mounts when I installed Koni's, but the only rubber I remembered was the spring seat and I thought maybe a little around the hole the strut goes through.