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?
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).]
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).]
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, ..
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).]
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)
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.
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.
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.
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.
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.
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 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).]
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.
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?
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?
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).]
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.
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"
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).]
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?
The photo shows that, but the shorter one just had to be compressed more to be assembled. That's a function of having less rebound travel and more jounce travel than stock. Install them and put weight on them and the two will have exactly the same ride height.
OK, I was wrong. The flip Does Not lower the car. After looking at what was said in this thread I now understand where I was misunderstanding. I can be a little hard headed but with enough persuasion I can be reached. Thanks for the clarification on the matter Without changing the lower spring perch on the strut OR the strut tower in the car ( basically the top of the spring rests under it ) moving the hat does not affect ride height.
This thread would have been MUCH better if I were right, but sense I am the one that is wrong, it is just OK
Hey Rick, don't feel bad. I suspect a lot of people believed what you initially thought... that's why I wanted this discussion!
Over the years I had seen it mentioned numerous times that people had flipped over the top plate for the struts and I wondered why. As as been pointed out in this thread, it doesn't make any difference in how the rear of a Fiero sits. However...
When shorter rear springs are installed, flipping the top plate over helps to put a pre-load on the springs which keeps them in place. When I cut the rear springs in my '84, it was a nuisance every time I jacked the back of the car up as the rear springs would come off their perches in the struts. When I flipped over the top plates, this reconfigured the strut assemblies and the rear springs were now held in place. However...
What I was unprepared for was the fact that the decklid would no longer close. With the "knob" of the top plate sticking up, the end of the strut now hit the decklid. I'm sure someone has mentioned this previously over the years, but I don't recall ever reading it here (prior to this thread). Interestingly enough, Pontiac put a partial "hole" exactly where this contact is made, and by drilling out another layer of material (with a hole saw), the hole is then deep enough to allow the decklid to fully close. The drilled out hole is pictured below. You can easily tell when you've drilled out the necessary layer. Just don't drill any further!
Here are three shots of the top of my 84's struts. You can see how the "knob" sticks through.
Compare that last shot with the end of the strut on my '88 Formula that hasn't had the top plate flipped over. If you have a good eye you'll notice that if the top plate was flipped over, the "knob" would hit the flat edge of the grill. A little trimming of this area would be required.
One factor which no one has touched upon is whether or not the action of the strut itself is affected by flipping over the top plate. At any given compressed height, the strut would be extended differently by at least an inch depending on which way the top plate had been installed. As I understand it, some struts (maybe all?) contain valves which have a variable rate depending on how far the struts are compressed. Monroe calls this "position sensitive damping". Is anyone brave enough to post an opinion on that?
[This message has been edited by Patrick (edited 11-23-2013).]
Originally posted by Patrick: One factor which no one has touched upon is whether or not the action of the strut itself is affected by flipping over the top plate. At any given compressed height, the strut would be extended differently by at least an inch depending on which way the top plate had been installed. As I understand it, some struts (maybe all?) contain valves which have a variable rate depending on how far the struts are compressed. Monroe calls this "position sensitive damping". Is anyone brave enough to post an opinion on that?
If the strut is sitting at a certain point at stock ride height, and the car is lowered, the strut will then sit at a lower point in its travel. Flipping the plate would bring the strut back up to a higher point in its travel. If you lowered the car by the amount the static position of the strut shaft changes when the plate is flipped, then the strut would be at its design "zero" position with the car lowered around it.
Originally posted by RCR: I thought this was done to gain the extra strut travel on lowered cars, so the strut has more travel before bottoming out.
Yes, the only reason to do this mod is to gain more strut range of motion in compression on a lowered fiero. No other need to do it
quote
Originally posted by RCR: But, doesn't this allow the strut rod to go through the hood if/when the rubber fails?
No, the large washer at the bottom and the concave washer up top keep the strut shaft locked in the hat. The rubber just keeps it from moving side to side/front to back.
Originally posted by fieroguru: Yes, the only reason to do this mod is to gain more strut range of motion in compression on a lowered fiero. No other need to do it Plus can affect strut's "road feel." Example Some shock/strut designs use/used slots cut into cylinder walls to make a "sweet spot" in the middle of travel. That slotted section gets a softer ride and Lower cars could mess up that.
No, the large washer at the bottom and the concave washer up top keep the strut shaft locked in the hat. The rubber just keeps it from moving side to side/front to back. Is true only when rubber is bad.
Rust etc can make weld/metal on outside of bushing to fail and could cause above damage.
Get new hats for this reason, especially lowered cars and states that use high road salt in winters. New hats available thru Monroe etc.
If the strut is sitting at a certain point at stock ride height, and the car is lowered, the strut will then sit at a lower point in its travel. Flipping the plate would bring the strut back up to a higher point in its travel. If you lowered the car by the amount the static position of the strut shaft changes when the plate is flipped, then the strut would be at its design "zero" position with the car lowered around it.
I agree 100% with what you've posted Will, but you didn't actually state how this possibly affects the performance and/or "feel" of the strut.
I think Ogre's on the right track below...
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Originally posted by theogre:
...can affect strut's "road feel." Example Some shock/strut designs use/used slots cut into cylinder walls to make a "sweet spot" in the middle of travel. That slotted section gets a softer ride and Lower cars could mess up that.
So stated another way... If the suspension is lowered with cut and/or shorter springs, the strut might have a stiffer feel to it due to where the now more compressed strut sits at rest.
In conclusion, it would appear then that struts with variable rate damping can retain their smooth riding "sweet spot" on a lowered car if the strut top mounting plate is flipped over and the strut is extended a bit. I imagine the same should occur with front shocks if a spacer is used between the bottom shock mount and the lower control arm. (That would also help prevent the front shocks from bottoming out as discussed HERE.)
[This message has been edited by Patrick (edited 05-21-2014).]
Originally posted by Steven Snyder: Does any shock available for a Fiero even have position-sensitive damping? I seriously doubt it...
Yes.
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MONROE Sensa-Trac SHOCKS & STRUTS: Unique Groove Tube - PSD Precision tapered grooves in the pressure tube perform like an additional stage of valving for optimum ride tuning.
Source: Monroe Web site and Monroe's Technical Support Shock Absorbers
Maybe some others uses this plan and Monroe makes them for other brands, like NAPA...
Edit to add Gabriel's "G-Force technology" for 84-87 front and rear, 88 rear only
[This message has been edited by theogre (edited 07-21-2014).]
Mind if I revisit this one? In the pic at the top of the post, I would say that the strut with the flipped hat would lower the ride height. That's what the picture clearly shows. The distance from the upper mount to the knuckle is less, hence a shorter "installed" length. The only other variable I see would be that the flipped hat would cause more spring preload when assembled. Would that extra preload negate the lower ride height of the flipped hat?
The photo can be misleading, because your car doesn't drive around with the springs uncompressed.
The weight of the car will compress the spring to a certain height. The preload from the spring perch doesn't affect the spring rate of the spring. So the spring will still compress to the same height, no matter which orientation you install the spring perch.
So for example, let's say your rear springs compress to 8" with the weight of the car on them (this is just a rough guess). With the weight off them, maybe it's 11". And maybe flipping the strut hats changes it to 10.5". That's OK, because the springs will still compress to 8" with the weight of the car on them.
The actual benefit from the spring perch flip is to get the strut piston back in the "sweet spot" after lowering the suspension.
[This message has been edited by Blacktree (edited 06-15-2016).]
Not at all... but as Blacktree has pointed out, physics haven't changed in the last three years.
I'm actually glad you resurrected this thread. I suspected back when I started the thread that there was much confusion regarding this issue. The resulting discussion demonstrated there was... and apparently, there still is!
[This message has been edited by Patrick (edited 06-16-2016).]
...my '88 Formula that hasn't had the top plate flipped over. If you have a good eye you'll notice that if the top plate was flipped over, the "knob" would hit the flat edge of the grill. A little trimming of this area would be required.
And just for the heck of it, that image can now be compared to this one taken 2 1/2 years later... with the top plate flipped. Notice how the grill has had to be trimmed.
And now for the question we've all been waiting for! Did the ride height change at all or remain the same? In other words, did the increased preload compensate for the shorter installed height? I understand the original purpose, to move the strut piston closer to the "sweet spot" in the travel. ------------------ 1984 Indy Fiero
[This message has been edited by ag9123 (edited 06-17-2016).]
And now for the question we've all been waiting for! Did the ride height change at all or remain the same?
Yes, the ride height changed... because rear lowering springs were also installed.
quote
Originally posted by ag9123:
...did the increased preload compensate for the shorter installed height?
As has been previously mentioned (in a variety of ways), the "increased preload" on the springs has no bearing once the struts are installed. The weight of the car compresses the springs well beyond that "preload" position. So for example (and I'm picking numbers out of the air here), if the weight of the car compresses 15" springs down to 10", it doesn't matter if the top mounting plates were restricting/compressing the length of the springs to 14" or 13" or 12". That "preload" on the springs of the uninstalled struts is completely overcome (and nullified) once the weight of the car has compressed the springs more than what the top mounting plates alone were doing.
[This message has been edited by Patrick (edited 06-17-2016).]
When flipping the strut plate, the bottom surface of the bumpstop moves up as well.
Does this create the potential for the tire to hit/rub the plastic wheelwell liner, or perhaps other issues? 84-87 toe-link hitting the frame rail? My Fiero is covered in snow; can't look now.
