Rear Upper Strut Mount (coilover q)

[Lance Cheney]

Hellow everyone. I'm in the process of putting on a set of IPT coilovers on my SHO (and finding problems with a few pieces of the kit, but that's another story).

I have a question on the rear mount. The stock rear mount is a big cup, with a painfully recessed strut mounting location, and the strut extends through the lower spindle about 4-5". The coilover kit duplicates that by putting a thick aluminum washer on top of the mounting plate and using longer bolts.

Is there a point to this setup, other than to 'look' like the OEM one? If I didn't use the spacer and then mounted the strut about the same amount higher in the knuckle, this would give me functionally the same results (once I readjusted the camber for the longer pivot length). It would make future swaps (spring or Koni insert) a lot easier too, as you don't have to pull the housing out of the knuckle as far.

Just wanted to make sure I wasn't missing something important. I'm pretty sure the struts will have some clearance at the top still; it would still be adjustable although the adjuster **** obviously won't fit on anymore.

At the very least, the spacer could be cut down.

-Lance

 

[Hack]

Interesting question. Unfortunately I do not have the answer, but I will being watching to see if anyone else does! thumb

I have yet to make the time to put mine in. Soon though, very soon......

 

[Lance Cheney]

I started taking mine apart tonight and found that the boot/strut cover has been collecting water -- probably 75cc worth of the stuff. The 1-year old Koni looks pretty nasty.

Anyway, the one thing I did notice is that I would have to move the sway bar attaching position, of course. That's easy enough to grind off and weld on farther down the tube. I also thought it through a bit more and figured out that the camber change from suspension movement would be less due to the longer pivot arm. I'm not sure if that is good or bad overall, as I'd normally be running 1.5 or more degrees of negative camber on the street, and probably 2.5+ on the track. The extra 2" (of 26 or so total) won't make much difference.

On a side note, the rear Konis seem to have very little compression damping, or at least the one I've got apart so far does. I put it upside down in a vice (supporting the shaft on the vice top, not clamping it, of course!) and can compress it full travel in all of about 1/4 second by applying most of my body weight to it. Seems a little weak to me. The tension side seems to be ok and does change with the adjusting ****. Any idea if this is normal? I'll compare it to the other side tomorrow but this makes me really want a double-adjustable setup if I'm going to put 400lb springs on the back.

-Lance

 

[SHO NUT]

Lance Cheney:
Hellow everyone. I'm in the process of putting on a set of IPT coilovers on my SHO (and finding problems with a few pieces of the kit, but that's another story).

I have a question on the rear mount. The stock rear mount is a big cup, with a painfully recessed strut mounting location, and the strut extends through the lower spindle about 4-5". The coilover kit duplicates that by putting a thick aluminum washer on top of the mounting plate and using longer bolts.

Is there a point to this setup, other than to 'look' like the OEM one? If I didn't use the spacer and then mounted the strut about the same amount higher in the knuckle, this would give me functionally the same results (once I readjusted the camber for the longer pivot length). It would make future swaps (spring or Koni insert) a lot easier too, as you don't have to pull the housing out of the knuckle as far.

Just wanted to make sure I wasn't missing something important. I'm pretty sure the struts will have some clearance at the top still; it would still be adjustable although the adjuster **** obviously won't fit on anymore.

At the very least, the spacer could be cut down.

-Lance

The most obvious is that you will loose droop travel (while gaining compression travel). This may be an issue on the street, since I've heard complaints about thunking on strut extension in the rear from Koni setups with short body inserts installed in long body housings, which somewhat effectively duplicates your adjustment in travel range by pulling the shorter insert body down into a deeper housing, where you pull the strut rod up .... (Koni's year cutoffs for rear long/short body housings don't quite match what Ford actually made, so there are some mis-matched setups out there .... if you check out our website, we list the difference based on the physical characteristics of the strut - not the year of the car)

As for the adjuster not fitting any more - that's probably due to interference with the seat belt retractor hardware that is a problem with the Gen II cars even with the stock setup - if you trim the cover on the bottom of the retractor, this is no longer an issue on the stock Koni setup, BTW. If you only end up trimming the ring, you may find that a Neon ACR adjuster (the flat one, not actually specific to the ACR) may work in the rear. These are nice units - due to the lack of a 'stem', they fit in the pocket quite nicely, and fit the front, of course, which then becomes pretty close to what you are trying to duplicate in the rear wink

 

[Lance Cheney]

SHO NUT:
The most obvious is that you will loose droop travel (while gaining compression travel). This may be an issue on the street, since I've heard complaints about thunking on strut extension in the rear from Koni setups with short body inserts installed in long body housings, which somewhat effectively duplicates your adjustment in travel range by pulling the shorter insert body down into a deeper housing, where you pull the strut rod up ....

</strong>

I have the long-style struts and inserts, but I'm a little confused as to why I would lose droop travel if I am moving the strut up in the knuckle (this would increase droop travel) and then removing the spacer (decrease droop travel by the same amount). But I hadn't thought of trying to bias travel by changing that proportion.

<strong>
As for the adjuster not fitting any more - that's probably due to interference with the seat belt retractor hardware that is a problem with the Gen II cars even with the stock setup - if you trim the cover on the bottom of the retractor, this is no longer an issue on the stock Koni setup, BTW.

Amazingly, my knobs fit with the stock springs/upper mount. Barely. I have 3 or 4 knobs laying around, so I managed to squeeze one in each side and just left them there. Removing the spacer would eliminate that ability.

After thinking about this some more I think that the benefits are less than I was hoping for. IT looks like I can't get the strut off the knuckle without unbolting the control arms anyway, even with 2" less movement required (enough to pull the knuckle off the tension rod, and then it can move down far enough to pull the strut off). It's only 2 nuts.

The camber gain/loss curve change is probably too subtle to worry about too.

Thanks for the info. I may need to get another **** if IPT's rear plate moves the top of the strut up or down at all. I had also forgotten about the long vs. short housing, and since I may make a trip to the junkyard to get a less-rusted strut housing, this would be a critical...

-Lance

 

[SHO NUT]

Lance Cheney:

SHO NUT:
The most obvious is that you will loose droop travel (while gaining compression travel). This may be an issue on the street, since I've heard complaints about thunking on strut extension in the rear from Koni setups with short body inserts installed in long body housings, which somewhat effectively duplicates your adjustment in travel range by pulling the shorter insert body down into a deeper housing, where you pull the strut rod up ....

</strong>

I have the long-style struts and inserts, but I'm a little confused as to why I would lose droop travel if I am moving the strut up in the knuckle (this would increase droop travel) and then removing the spacer (decrease droop travel by the same amount). But I hadn't thought of trying to bias travel by changing that proportion.

Whoops, I didn't get the part that you were moving the strut up in the knuckle .. if that's the case, the available droop travel would be the same, provided that you move it up exactly the same as the amount of the ring you remove ...

However, as you point out, removing the ring, and being able to adjust the position of the housing in the knuckle gives you the ability to adjust your bias between available droop and compression travel ...

 

[billyshoe]

Leave the lower alone, change the upper. The upper mount is cupped about 2"-Elimininate this. Go from there.

 

[SHO NUT]

billyshoe:
Leave the lower alone, change the upper. The upper mount is cupped about 2"-Elimininate this. Go from there.

If you do that, then you reduce available droop travel, as I posted above ....

<small>[ February 14, 2004, 06:56 AM: Message edited by: SHO NUT ]</small>

 

[gmorrell]

Lance,

whatever path you take, in terms of moving the upper and lower strut mounting points, please do a dry fit of the strut assembly w/coilover spring perches into the suspension, but without the spring. Then move the suspension through its full range of motion to ensure there are no problems or interferences.

Sans spring is also a good time to get a handle on spring perch movement and suspension motion ratio, both of which will get you to a close approximation of the spring installed heights (loaded) and where to set the lower perches to get the ride height you desire. Doing this may also lead you to wanting longer springs.


The rear upper mounts I did for my coilovers move the Koni adjustment tang well above the top of the strut tower sheet metal in the trunk. I did this for a number of reasons:
1. It made the upper mount very simple and light. (Its billet Al 6061-T6)
2. Relocating the strut piston rod upwards improves bump travel on lowered suspensions.
3. It allowed me to use the longest possible spring.
4. I got tired of fishing for the adjustment tang down inside the strut tower.

Droop travel shouldn't be an issue with the longer style Koni inserts, unless you're worried about your suspension poise while your doing Dukes of Hazzard bridge jumps.

Do keep in mind that Koni inserts don't have internal droop limiters, so the piston can be damaged if the suspension goes violently into droop. The ideal situation is if the main spring is still slightly in compression when the suspension is at full droop, as this keeps the travel range controlled and predictable. While ideal, this isn't always realizable with coilovers, and you may want to consider using the longest springs that are practical with some helper springs to keep the main springs in their seats at full droop.

<small>[ February 14, 2004, 10:48 PM: Message edited by: Gary M. ]</small>

 

[SHOguy 92]

I have no clue about half the suspension terms you people are talking about, but I do wonder where you people are getting these coilovers and how much they are because IPT's weebsite isn't working.

 

[Hack]

SHOguy11:
I do wonder where you people are getting these coilovers and how much they are because IPT's website isn't working.

Josh, I do not think that anyone is currently producing coilovers for the SHO. They are expensive because they are done in relatively small runs. If you are serious about getting a set, Ground Control Suspension might be able to help you out. IPT's website is not functioning because they are not making any SHO parts any more. The company may not exist at all anymore.

 

[Lance Cheney]

yellowSHO:

SHOguy11:
I do wonder where you people are getting these coilovers and how much they are because IPT's website isn't working.

Josh, I do not think that anyone is currently producing coilovers for the SHO. They are expensive because they are done in relatively small runs. If you are serious about getting a set, Ground Control Suspension might be able to help you out. IPT's website is not functioning because they are not making any SHO parts any more. The company may not exist at all anymore.

We can hope...

I had to replace several of the misc. 'hardware' pieces that came in my coilover kit because they weren't really the right size for the job. Additionally I found today that one of the welds on the rear top mount is cracked, so that will have to be redone. Looks like it had too little *********** and too much heat distortion when the other side of the spherical bearing was welded to the top plate.

I got the last of their sets. It really is not that hard to put together -- the spring perch, top hat, and aluminum rings were all from Bicknell racing, and the only real piece of engineering was the top plates (which on the back is just a 3/16" piece of steel plate with an Aurora spherical bearing in the middle and the three long bolts, plus aluminum spacer. I'm not sure how much Bicknell charges for their stuff, but the rest of it could be put together, including springs, for pretty darn cheap (less than $350, assuming $200 for the springs), so long as you had somewhere to machine the parts.

I was thinking about trying to make a few but (A) I don't have a lot of experience (my degree is in electrical, not mechanical engineering), and (B) how much demand is there, really, for something like this?

-Lance

 

[billyshoe]

Droop?? what is this?

<small>[ February 19, 2004, 01:01 PM: Message edited by: billyshoe ]</small>

 

[gmorrell]

billyshoe:
Droop?? What is this?

You've probably been getting about 10 emails a day on how to cure it... [rimshot]

From a static situation (car at rest, suspension not moving), suspension movement is referenced in two directions with respect to the main spring or the car body; compression and droop. Compression = suspension moving up, droop = suspension moving down.

Full compression is reached when the suspension hits the bumpstop or the spring goes into coil bind. (The latter is a bad thing...)

Full droop is reached when the strut or shock reaches the limit of its mechanical travel in extension.

<small>[ February 19, 2004, 01:35 PM: Message edited by: Gary M. ]</small>

 

[gmorrell]

Lance Cheney
I had to replace several of the misc. 'hardware' pieces that came in my coilover kit because they weren't really the right size for the job. Additionally I found today that one of the welds on the rear top mount is cracked, so that will have to be redone. Looks like it had too little *********** and too much heat distortion when the other side of the spherical bearing was welded to the top plate.

The sphericals were welded to the camber plates? Good Lord...

I got the last of their sets. It really is not that hard to put together -- the spring perch, top hat, and aluminum rings were all from Bicknell racing, and the only real piece of engineering was the top plates (which on the back is just a 3/16" piece of steel plate with an Aurora spherical bearing in the middle and the three long bolts, plus aluminum spacer. I'm not sure how much Bicknell charges for their stuff, but the rest of it could be put together, including springs, for pretty darn cheap (less than $350, assuming $200 for the springs), so long as you had somewhere to machine the parts.

You might be surprised how expensive this can get. Race grade 3/4" bore Teflon lined sphericals are going to be over $20 each, even in quantity, you need four per car. If you want to avoid welding things together and instead use billet Aluminum camber plates with pressed in sphericals as I did, the material and machining costs add up pretty quickly. You will need some miscellaneous bushings to adapt everything together; figure materials, machining and plating to make them pretty. You'll need coilover kits with threaded sleeves and upper & lower spring perches. Decent 2.5" I.D. race springs (Hypercoils, Eibachs) are $50 to $60 each. About $10 worth of good grade Metric mounting hardware goes into the kit. It adds up quickly.

If I were to cut P.O.'s for 10 sets of SHO coilover parts with my machine shop and other parts suppliers, I'd be in for a hefty $4-figure sum in a hurry, and I'd want to have 50% cash commitments in the bank for every one of those coilover kits, or it isn't happening.

Fact is, I would do as I did with the last coilover build (5 sets), which was privately sold: I would sell through Josh at SHONut. I've no desire to be a retailer.

 

[Lance Cheney]

Gary M.:

Lance Cheney
I had to replace several of the misc. 'hardware' pieces that came in my coilover kit because they weren't really the right size for the job. Additionally I found today that one of the welds on the rear top mount is cracked, so that will have to be redone. Looks like it had too little *********** and too much heat distortion when the other side of the spherical bearing was welded to the top plate.

The sphericals were welded to the camber plates? Good Lord...

</strong>

The best part is that the weld is really only there for the tension side. It appears that the bearing comes with a lip on the lower side so in compression that lip would transfer all of the force anyway (though this is odd, because Aurora's documentation doesn't show this). The weld is just to keep it from pulling back out in tension. You shouldn't need a 1" long bead for that (although you do need *something*, and that something shouldn't be cracked). A few short welds would be less likely to damage the race and/or teflon lining. Since the ball is 1" diameter and the whole bearing is 1-3/16" dia, there isn't a lot of room in there before you start destroying stuff. He's using a 5/8" standard-grade bearing (COM-10T). There's no axial load rating posted. They are about half the price of a good bearing (eg. NMB ABT bearings). A 5/8" ABT10 bearing is about twice as strong and costs about twice as much (up to the $20+ you were quoting). It has an Ultimate axial load rating of 7080 lbs, or safe rating of somewhere under 4000 lbs -- this seems very safe for the SHO (thinking in terms of a 2G bump), but maybe that is too conservative. I can't see needing a 3/4" version of this bearing unless you were getting into extreme forces from coil-bind or you were doing offroad rally racing on a regular basis nono rofl . What sort of axial retention force requirement are you using in your press-fit setup (and this is steel into your aluminum top plate, right)? Also, what did you use to adapt a 3/4" bore spherical bearing to a 14mm strut shaft?

Looking into this more does make me think that using a COM-10T on the front of these things is a long ways on the underengineered side. Anybody gone rally racing with these yet? shrug

You might be surprised how expensive this can get. Race grade 3/4" bore Teflon lined sphericals are going to be over $20 each, even in quantity, you need four per car. If you want to avoid welding things together and instead use billet Aluminum camber plates with pressed in sphericals as I did, the material and machining costs add up pretty quickly. You will need some miscellaneous bushings to adapt everything together; figure materials, machining and plating to make them pretty. You'll need coilover kits with threaded sleeves and upper & lower spring perches. Decent 2.5" I.D. race springs (Hypercoils, Eibachs) are $50 to $60 each. About $10 worth of good grade Metric mounting hardware goes into the kit. It adds up quickly.

Ok, I found some sleeve kits -- they are a bit more than I was figuring ($40+ ea). I got Hypercoils for $50 ea shipped, so the parts cost is getting up there ($50 spring + $25 bearing + $50 sleeve kit + $25 misc hardware per corner), and I can believe that any custom machining will push it up significantly, but even going the cheaper route (steel, with the bearing welded in or pressed in) would still be spendy. I stand corrected. oh

What did you plate your aluminum pieces with? These steel pieces came with what looks like a zinc dichromate coating. All of the parts from the BRP coilover sleeve kit came anodized already, of course.

-Lance

<small>[ February 19, 2004, 06:10 PM: Message edited by: Lance Cheney ]</small>

 

[billyshoe]

Droop is the same as rebound. huh? or is it the arc motion it needs to make during the piston travel? what?

<small>[ February 23, 2004, 03:57 PM: Message edited by: billyshoe ]</small>

 

[billyshoe]

billyshoe:
Droop is the same as rebound. huh? or is it the arc motion it needs to make during the piston travel? what?

scratch all that, I understand the term.

<small>[ February 24, 2004, 12:15 PM: Message edited by: billyshoe ]</small>

 

[Lance Cheney]

Gary M.:
Lance,

...
Do keep in mind that Koni inserts don't have internal droop limiters, so the piston can be damaged if the suspension goes violently into droop. The ideal situation is if the main spring is still slightly in compression when the suspension is at full droop, as this keeps the travel range controlled and predictable. While ideal, this isn't always realizable with coilovers, and you may want to consider using the longest springs that are practical with some helper springs to keep the main springs in their seats at full droop.

Hi Gary,

I'm not sure that I understand this. The strut must have something to keep the guts from pulling out, and that something usually has a significant amount of force on it even in the stock configuration, since the spring is in compression and is attempting to pull the strut apart. How does having a longer spring help reduce the force exerted on the strut at the limit of its travel? Having a short spring (one that is completely unloaded at full droop) means that the only weight on the strut is the wheel + spindle assembly, vs. an additional 150+ lbs of spring force (I can't unload the stock top plate completely with my weight on it) accelerating that mass to the droop limit with nothing to stop it other than the bushing compliance in the tension rod and control arms?

What am I missing?

-Lance

<small>[ February 23, 2004, 06:59 PM: Message edited by: Lance Cheney ]</small>