 
     |
| Does flipping over the strut top mounting plate change the Fiero's rear height? (Page 1/6) |
|
Patrick
|
NOV 21, 02:17 AM
|
|
I'm curious what people will say... Does flipping over the strut top mounting plate alter the Fiero's rear riding height at all?
I have my own opinion, but I'll save it for later after some of you have expressed your views.
Below are an extra pair of struts from an '88. The "factory" setup is on the right. They are both fully extended, and the red line clearly shows the difference in total length. (Just for clarification, the top and bottom rubber pads have been also been removed from the spring in the strut assembly on the left, but that has no bearing on the difference in the length of full extension.)
Would a Fiero sit at exactly the same height in the back with a set of struts set up either way, and if not, why not?
|
|
|
Rickady88GT
|
NOV 21, 02:28 AM
|
|
| quote | Originally posted by Patrick:
I'm curious what people will say... Does flipping over the strut top mounting plate alter the Fiero's rear riding height at all?
I have my own opinion, but I'll save it for later after some of you have expressed your views.
Below are an extra pair of struts from an '88. The "factory" setup is on the right. They are both fully extended, and the red line clearly shows the difference in total length. (Just for clarification, the top and bottom rubber pads have been also been removed from the spring in the strut assembly on the left, but that has no bearing on the difference in the length of full extension.)
Would a Fiero sit at exactly the same height in the back with a set of struts set up either way, and if not, why not?
|
|
This is how I run my 88 and yes it does lower it a little. I also have the front springs from an 88 in the rear and the front springs from an 87 in the front of my 88. So all four springs in my 88 are front springs. I did have to cut the 87 springs to fit in front of the 88.
With the cut stock 88 springs, I would bottom out the shocks, now with the stiffer setup I have not bottomed out yet.[This message has been edited by Rickady88GT (edited 11-21-2013).]
|
|
|
|
fieroguru
|
NOV 21, 06:27 AM
|
|
There should not be any change in ride height. The hat that is flipped sits between the bottom of the strut tower and the top of the spring perch and is about 1/8" thick at this point. So when you flip it, the distance between the bottom of the strut tower and the top of the spring perch does not change (still 1/8" thick). The spring's compression as it sits on the upper and lower spring perches is what determines ride height, so since the upper spring perch placement hasn't changed, ride height should not change either.
In the picture what has changed is the pre-load of the spring on the strut. Since the spring will further compress as it supports the vehicle weight, this pre-load difference does not have a significant impact on ride height as long as the pre-load does not exceed the weight it will support at ride height.
What does change is the range of motion for the strut. Since the hat has the bushing end for the strut to attach to, and the hat normally protrudes down into the spring area, the end of the polish strut shaft is about 1 1/2" below the bottom of the strut tower. When you flip the hat, the bushing protrusion now sticks out the top side of the strut tower, and the top of the machined strut shaft is within 1/2" of the bottom of the strut tower. This means that the strut will bottom out with the wheel compressed 1" further towards the strut tower, and will hang off the strut at at full droop 1" closer to the strut tower as well.[This message has been edited by fieroguru (edited 11-21-2013).]
|
|
|
|
2.5
|
NOV 21, 08:56 AM
|
|
| quote | Originally posted by fieroguru:
What does change is the range of motion for the strut. Since the hat has the bushing end for the strut to attach to, and the hat normally protrudes down into the spring area, .. |
|
It would be a slightly firmer ride, right?
|
|
|
|
Rickady88GT
|
NOV 21, 11:13 AM
|
|
| quote | Originally posted by fieroguru:
There should not be any change in ride height. The hat that is flipped sits between the bottom of the strut tower and the top of the spring perch and is about 1/8" thick at this point. So when you flip it, the distance between the bottom of the strut tower and the top of the spring perch does not change (still 1/8" thick). The spring's compression as it sits on the upper and lower spring perches is what determines ride height, so since the upper spring perch placement hasn't changed, ride height should not change either.
In the picture what has changed is the pre-load of the spring on the strut. Since the spring will further compress as it supports the vehicle weight, this pre-load difference does not have a significant impact on ride height as long as the pre-load does not exceed the weight it will support at ride height.
What does change is the range of motion for the strut. Since the hat has the bushing end for the strut to attach to, and the hat normally protrudes down into the spring area, the end of the polish strut shaft is about 1 1/2" below the bottom of the strut tower. When you flip the hat, the bushing protrusion now sticks out the top side of the strut tower, and the top of the machined strut shaft is within 1/2" of the bottom of the strut tower. This means that the strut will bottom out with the wheel compressed 1" further towards the strut tower, and will hang off the strut at at full droop 1" closer to the strut tower as well.
|
|
I disagree with you on this. 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.
The shock travel length does not change, and the threaded end of the shock shaft has a shoulder that rests inside of the hat mount so it does not matter what orientation the hat sit in. The difference that lowers the car is where the shock hat flange is in relation to the end of the shock shaft. The closer that flange is to the shock body, the lower the car will be. That is clearly evident in the pic, the red line depicts the strut tower of the car. The shock shaft and nut sit higher above the strut tower by the same distance that the car is lowered.
I know that it does not lower the car by much but it does lower the car about .5. I have done this and took measurements at the wheel arch before and after the hat flip and it did change.
As you said it also preloads the spring tighter at the same time.[This message has been edited by Rickady88GT (edited 11-21-2013).]
|
|
|
theogre
|
NOV 21, 11:26 AM
|
|
Check clearance when lid is closed...
Flipping that can make the strut to hit the trunk lid, etc.------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)
|
|
|
|
zkhennings
|
NOV 21, 11:39 AM
|
|
| quote | Originally posted by Rickady88GT:
I disagree with you on this.
The shock travel length does not change, and the threaded end of the shock shaft has a shoulder that rests inside of the hat mount so it does not matter what orientation the hat sit in. The difference that lowers the car is where the shock hat flange is in relation to the end of the shock shaft. The closer that flange is to the shock body, the lower the car will be. That is clearly evident in the pic, the red line depicts the strut tower of the car. The shock shaft and nut sit higher above the strut tower by the same distance that the car is lowered.
I know that it does not lower the car by much but it does lower the car about .5. I have done this and took measurements at the wheel arch before and after the hat flip and it did change.
As you said it also preloads the spring tighter at the same time.
|
|
I fully agree with guru.
Does not change ride height and it does change suspension travel. Unloaded length is shorter but that is it. Distance spring compresses is f/k= x where f is weight of car and k is spring constant. It is simple physics. Neither of these things change, nor does the surface the spring sits against (It is really sitting on bottom of strut tower and that height doesn't change) Suspension travel changes because the bushing is not taking up the top hat to shock body distance. Install both those struts and it will be obvious the ride height is the same and the suspension travel is greater on the upside down top hat.
|
|
|
|
Rickady88GT
|
NOV 21, 12:02 PM
|
|
| quote | Originally posted by zkhennings:
nor does the surface the spring sits against (It is really sitting on bottom of strut tower and that height doesn't change) Suspension travel changes because the bushing is not taking up the top hat to shock body distance.
|
|
I am not sure how to explain it in any other words, the distance between the bottom of the shock/strut where it mounts to the knuckle and the uppermost surface of the spring perch mount ( the flange with the three studs in it) is about .5 shorter after the flip. That will directly relate to a .5 drop in ride height. I do not disagree with what happens with the spring between those two points.
The end result is basically the opposite of adding spacers between that three stud flange and the strut tower. In the hat flip you change the location of the flange, to a shorter overall length. That will lower the car.
|
|
|
|
fieroguru
|
NOV 21, 12:20 PM
|
|
| quote | Originally posted by Rickady88GT:
I disagree with you on this. 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.
The shock travel length does not change, and the threaded end of the shock shaft has a shoulder that rests inside of the hat mount so it does not matter what orientation the hat sit in. The difference that lowers the car is where the shock hat flange is in relation to the end of the shock shaft. The closer that flange is to the shock body, the lower the car will be. That is clearly evident in the pic, the red line depicts the strut tower of the car. The shock shaft and nut sit higher above the strut tower by the same distance that the car is lowered.
I know that it does not lower the car by much but it does lower the car about .5. I have done this and took measurements at the wheel arch before and after the hat flip and it did change.
As you said it also preloads the spring tighter at the same time.
|
|
The amount of available strut travel is what it is and remains unchanged, but where ride height places the strut in its range of travel does change. Say the strut has 5" of total travel in stock form and the stock ride height has 2 1/2" of available travel in compression and rebound. Lower the car 1" by changing the springs, now the strut has 1 1/2" of travel in compression and 3 1/2" in rebound. Depending on stiffness of the springs, you now have a much greater chance of bottoming out the strut on compression. By flipping the hat, you move the top of the strut shaft up (relative to the strut tower) by about 1" and re-center the range of motion for the strut so you have 2 1/2" of travel in compression and 2 1/2" in rebound... just like stock, but with the 1" lowered stance. The hat flip mod allows better use of the available range of motion for the strut in a lowered application.
If you look at the spring perch placement on the strut with it out of the car, then yes it did move, for that frame of reference.
Now look at it from an as installed and at the ride height perspective, which is a function of supported weight, spring rate & length, and distance from the upper and lower spring perches. The upper spring perch remains about 1/8" below the fixed placement of the strut tower, so its placement relative to the chassis remains unchanged. The lower spring perch remains in the same place on the strut, and the spring length/spring rate didn't change - so the distance between the upper and lower spring perch should remain the same with the suspension loaded at ride height. If you don't perform any mods to relocate the placements of the spring perches, then the only way for ride height to change is if the distance between the two perches changes, and that distance is determined by the spring length, spring rate, and weight of the vehicle.
For most springs used in Fieros and typical fiero weight, preload on the assembled strut should not have any impact on the ride height, it just allows the use of a softer spring (which needs more compression to support the weight) while keeping the strut within the middle of its range of motion at ride height. You can test this by just removing the nut at the top of the strut shaft (which eliminates the preload on the spring caused by the strut) and see if the car will raise up by doing so. I have done this before and it doesn't change the ride height.
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. Now during the process of performing the flip, there are a several of other actions that could result in the car riding higher after the work like: the springs not being properly seated in the upper/lower seats, replacing the rubber spring isolators at the top and bottom of the spring with new/stiffer/thicker material, or replacing an old degassed strut with one with a full charge that takes some additional force to keep compressed.
Clearance to the decklid does need to be checked. On Fastback 88's the hat filp mod clears just fine, but all others are suspect. It clears on my 88 Notchie, but my struts are 1” further inboard than stock.
|
|
|
|
zkhennings
|
NOV 21, 12:38 PM
|
|
|
Yup does not clear on my 85 Notchie decklid with no relocation of struts when I tried this.
|
|
|
|