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| Does flipping over the strut top mounting plate change the Fiero's rear height? (Page 2/6) |
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Rickady88GT
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NOV 21, 12:45 PM
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| quote | Originally posted by fieroguru:
The hat flip in an of itself should not change the ride height because...
it can be flipped without changing the upper spring perches relative position to the strut tower.
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The point I am trying to make is that flipping the hat does change the relative position of the spring perch and mounting flange. The top mounting point (the three stud flange) and the bottom mounting point (knuckle) are closer together after the flip by about .5.
I understand that spring rate and other factors will affect ride height, so depending on springs used results will very. But all things equal, if you simply removed the strut from your car and flipped the hat then reinstall, your ride height will change.
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Patrick
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NOV 21, 03:41 PM
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This is exactly the discussion I was hoping would be generated. Thanks for keeping it civil, guys!
I'll refrain from giving my opinion until we perhaps hear a little more from other people.
This is almost as good as the plane on the conveyor belt.  [This message has been edited by Patrick (edited 11-21-2013).]
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Rickady88GT
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NOV 21, 04:35 PM
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| quote | Originally posted by Patrick:
This is exactly the discussion I was hoping would be generated. Thanks for keeping it civil, guys!
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Well it is for now but if people don't start seeing it my way...LOL
| quote | Originally posted by Patrick:
I'll refrain from giving my opinion until we perhaps hear a lilttle more from other people.
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So you must want me to stand down? LOL 
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Patrick
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NOV 21, 04:43 PM
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| quote | Originally posted by Rickady88GT:
So you must want me to stand down? LOL
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No no no, keep at it. 
I'm just hoping to hear opinions from other people as well.
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Will
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NOV 21, 04:52 PM
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| quote | Originally posted by Rickady88GT:
The spring perch does change location. It is placed lower/further down the shock shaft. That is why the shock shaft sticks up further above the hat.
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The spring perch does NOT change location. The perch is the same distance above the camber bolts as it was. The camber bolts are the same distance above the ground as they were. The same weight will compress the spring to the same compressed length. The thickness of material between the top of the spring and the bottom of the strut tower is the same. Therefore, the distance from the ground to the bottom of the strut tower is the same.
The strut will be more extended with the flipped plate than it was with the plate in the stock orientation, allowing for greater jounce travel before hitting the bump stop. This is advantageous to a lowered car. However, as Ogre pointed out, the top of the strut may hit the underside of the decklid.
I don't think the bushing fits through the hole in the strut tower... wouldn't you have to holesaw the strut tower to fit it through?[This message has been edited by Will (edited 11-21-2013).]
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Rickady88GT
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NOV 21, 05:01 PM
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| quote | Originally posted by Will:
The spring perch does NOT change location. The perch is the same distance above the camber bolts as it was. The camber bolts are the same distance above the ground as they were.
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Could you draw this up for me please? Or edit the pic to show exactly what you said?
I believe that the pic shows the flange does change position in relation to the camber bolt. Maybe I just misunderstand what you said?
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lateFormula
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NOV 21, 05:13 PM
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| quote | Originally posted by Rickady88GT:
I believe that the pic shows the flange does change position in relation to the camber bolt. Maybe I just misunderstand what you said?
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In the pictures at the top of the thread it appears that the spring perch is closer to the camber bolts. BUT the spring+strut on the left side of the picture is pre-loaded considerably more than the strut on the right side.
If the springs do not change, and the weight of the vehicle supported by the springs does not change, then flipping the mounting plate will not affect the ride height. In this suspension example the spring's resistance to the weight they are holding up is what sets the ride height.[This message has been edited by lateFormula (edited 11-21-2013).]
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Tha Driver
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NOV 21, 05:52 PM
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| quote | Originally posted by Rickady88GT:
The spring perch does change location. It is placed lower/further down the shock shaft. That is why the shock shaft sticks up further above the hat.
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This is wrong. With the weight of the car (using the same spring), the top spring perch does not change position relative to to the strut HOUSING - which is where the bottom spring perch is. The shock SHAFT is free floating, so it doesn't matter how it might be changed. The only way it will change ride height, is if the preload is greater than the weight of the car.
~ Paul
aka "Tha Driver"
Custom Fiberglass Parts
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fieroguru
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NOV 21, 06:15 PM
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Here is a visual... The roll of tape is the bottom side of the strut tower (so everything is upside down). I think we all agree that the strut tower doesn't move, and so measuring from my bench to a fixed location on the spring perch in the stock position and flipped position will help show if there is something involved in the flipping process that would move the perch from the strut tower (roll of tape).
Here is the hat and spring perch in the stock location with the protruding portion of the hat within the spring area:
All I did for this picture is flip the hat (protrusion goes above the strut tower) and put the spring perch back on top of it. No change from the previous position:
As you can see there is no relative movement, so flipping the hat didn't move the spring perch, so it should not change ride height.
The hat is not perfectly flat on the original top side, there is about 3/16" of a protrusion as seen in the picture below. The 88 strut tower is a multi-layer construction with the bottom side having a much larger hole and the top panel is tapered. This means that this slight protrusion does not keep the hat from bolting flat to the strut tower (like my roll of tape simulation).
Now, I do believe you saw a ride height change when you did the swap, so I am trying to look for reasons that could be. For starters I believe everyone is approaching this question under the assumption of stock rear springs or aftermarket lowering springs that actually use the stock upper spring seat for support. I believe you are approaching this question based on your particular car with 88 front springs mounted in the rear that may or may not be using the stock spring perch.
Expanding on the rear spring assembly some, there is a large bump stop washer that rests directly against the hat. This washer is too big to pass through the 88 front spring, but too small in diameter to fully support it either.
In stock form is sticks out like so with the following dimension to the bench (just a fixed reference point).
When you flip the hat and put it back together, this bump stop washer moves towards the strut tower surface about 3/4":
Now I don't know how exactly you mounted the 88 front springs in the rear, but if you used this washer surface to support them, then that is why you are seeing a change that you would not see if using stock type/diameter springs.
For starters you used front springs in the rear. What I don't know is how you went about centering them as the springs are much smaller in diameter and don't fit the perch well. Also if you[This message has been edited by fieroguru (edited 11-21-2013).]
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85sliverGT
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NOV 22, 08:10 AM
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| quote | Originally posted by Will:
I don't think the bushing fits through the hole in the strut tower... wouldn't you have to holesaw the strut tower to fit it through?
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Fits without modification on my 88
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