nvm

 

MINI rear struts are subjected to high side loads, restricting the strut shaft neck from pivoting creates bending stress upon the shaft, and subjects the piston to lateral stress, for which it was not designed to tolerate; it's a recipe for stiction. Softer is better for this application.

 

I might need to get some of these, the ride is horrible in my 2002, even with 40k miles on it. So the ride hight is more consistent, smoother or more predictable?

 

nvm

 

Increased side load will become apparent in time.

The upper mount is not the appropriate location for a spacer to alter ride height due to spring choice, sacked springs, and/or body trim contact from tire & wheel dimensions. Under the lower spring coil is the place for shims.

 

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Why would there be any side loading up there? That's right under the nut, isn't it? Seems to me that's a good place to have a stiff bushing....the shaft of the shock is still free to move about, only the end is pinned, it can still pivot tho can't it?

I don't see a downside here unless it increases NVH....

 

It is the springs that have sagged if the car is bottoming out, the poly bushing is acting as a shim in this case by not compressing. Yes I have first hand experience.

The trailing arm is attached forward of the lower shock mount, the top mount is attached forward of the lower mount, as the lower mount location rises, the top of the strut shaft must tilt, there is a metal spacer withing the upper mount bushing that is bolted against a washer collar and the upper spring perch creating a fairly rigid connection to the shaft. The ID shape of the washer/collar and OD neck of the OEM strut shaft (not Bilstein's BTW, which is square, and will be rigid), will allow a minor amount of give, but not enough to compensate for an upper spring hat that cannot move in its intended range of motion. There is a reason why the rear OEM spring hat has a radius edge, and the contact surface is less than the bushing's, that is so it can roll into the upper bushing for less resistance. The washer under the top strut nut is dished to allow less resistance to side movements also. When the shaft is not allowed to tilt feely, this increases side load on the shaft neck, the shaft against internals, its seals, and the piston within. These forces exist with the OEM strut as well, and they increase when the car is lowered, ideally this effect should be minimized. A coilover spring hat with inadequate clearance, a spring hat that is too wide, or a poly bushing that does not allow sufficient compression on the hat's edge, are movement inhibiting examples.

Note the conflicting report from the OP, we're told it does not inhibit movement, but we are shown the lack of compressibiliy in a photo.

 

Question: In order to replace/install these bushings, is it necessary to decompress and remove the spring from the strut assembly?

 

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Thanks.

 

R53Warrior -

k-huevo is correct with his answer. I have personal experience with snapping a shock in half due to the side load caused by the top hat not articulating when the suspension compresses. I noticed no issues while driving under the condition until the shock finally snapped.

The suspension doesn't move in a linear fashion when compressing due to the geometry of the rear trailing arm in relation to the upper mount.

Looking at your suspension from the back of your car at full droop it looks like this

[] / \ []

as the suspension travels upwards, the relation of the two straightens out

[] l l []

Where the shock passes through the top hat is now side loaded because it has nowhere to go.

If you look at other designs that ditch the factory top hat you'll notice that they go with something that is more along the lines of a heim joint / spherical bushing

 

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I am surprised that you work for a MINI dealer and are not more informed on the mechanics of the MINI.

Keith is right on about the bushing, but then I guess you will find out soon enough.

And I am really surprised on the language in your signature pic...........

 

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Thanks for the explanation, khuevo!

Seems R53 warrior picked up his posts and just went home.....