SVO-ish Suspension Rebuild

[Desert Patina]

So having rebuilt the engine, brakes, cooling fan system, engine wiring harness, and putting on Bo-Port head and a new t4/t3 turbo (just to fix the old stock wastegate actuator) ... it is a daily driver shuttling kids back and forth to school.

I asked my son, who is doing the driving, if he'd rather the air conditioned van and he said, "I'd rather the SVO because it is a difference of being cool, or being coooool". Can't argue with that.

But the suspension is just too tired. So like all of these rebuilds I'm in paralysis by analysis and would like to consult with the greater brain trust here...

I have essentially three options, a minimalist option, a junk-yard option, and a more full tilt for less tilt option...

Minimalist:
Mostly just new poly bushings, and getting a pair of spherical bushings for the back. Where to put the spherical bushings might be controversial, but I was thinking lower arms on the chassis. This means using the rebuild service through O'Reilleys (if they are still doing it) for the front control arms. That with the new Koni's (minus the quad rear because supposedly with the spherical bushings I don't need it anymore)

Junk-Yard:
Find whatever 1995+ GT or Cobra is in the junk yard and get their suspension (or even get lucky and find a MM suspension there, which I've seen a few times at least), and get some coil overs and the same bushing arrangement

Full Tilt:
Go with some trusted manufacturers grip package (Griggs, MM, Steeda, etc...) with a new aftermarket 3-link rear-end and coil-overs in the front

My goal really is just to appreciate a good suspension, rather than be really competitive with it. Even if I have all the money in the world, I don't see myself doing other than one or two track days a year, but I'd hate to miss out on a nice road when I find one. And most certainly my primary goal is to make something more safe at the limit and reduce binding.

Any opinions, consultation and guidance?
svodd.jpg

[Chuck]

IMHO, I have been driving my SVO since June of 1986, when it was purchased new. The suspension is all stock (even today) and still has the original Koni's. The only drive-train od was to swap in an 8.8 with 4.11 Roush posi (for driving around town).

I have never driven that car without feeling "Wow, this is an SVO"; even when I commuted to work in it 30 years ago. In my opinion, there is nothing wrong with the stock suspension (I can still turn onto a side street at 30 MPH without slowing down before turning). Put it back the way it was and the "Machine will speak for itself". The car now has 68,000 miles on the clock.

Chuck

[Desert Patina]

If it helps, it isn't for lack of appreciation of the SVO's suspension that I consider other options. The main reason is money and axle snap back (binding). My Koni's are shot. And between new Koni's (I wouldn't be able to cash in on the lifetime warranty) and $600 per side for rebuilding the control arms, I'm a far way to just putting money down on a good grip package.

Still, all things considered, SVO-ish minimalist build with mild improvements to the Jackie Stewart approved suspension is the option I'm leaning towards at the moment.

[KevinK]

Try Rareparts directly for the control arm rebuild. Maybe source some good used struts. While other parts might be cheaper there is still the conversion labor.

[Desert Patina]

Thanks for all the comments so far. Things may be coming into better focus...

Shocks have been the biggest technology drivers in suspension for the past 30 years. I'm okay updating to good Koni's. Besides, CJ Pony has a set for 44% off right now (I hope it lasts while my funds accumulate).

I've heard that I can bolt in subframe connectors and frame bracing from a 98+ convertible, that might be the one thing from the Junkyard list that survives any choice I make.

I saw someone in a previous thread that was discussing the PM3L (poor man's three link) which amounts to getting a panhard bar and using only one of the upper control arms as a torque bar. But it really isn't too much more money or hassle to get a panhard bar, but I'd need a good 8.8 that fits the SVO brakes if I did a real torque bar. I don't know how serious I am about this, I haven't shopped around for a panhard bar yet.

But that isn't the craziest of the serious suggestions. Seems even more PM is to just put pipe foam insulation in for rear control arm bushings. I can see that working for a 10-20 lap track day, but not for a daily driver.

[Mike S]

For me, the best money spent on my suspension upgrades was first the MM subframe connectors, then the MM panhard bar and rear lower control arms. This helped to reduce the the understeer on the front and snap oversteer at the limits on the rear. Also, adding the SN95 rear eibach rear sway bar upgrade aided in controlling understeer.

The MM torque arm was the next upgrade that helped with keeping the rear wheels on the ground during hard braking.

[Desert Patina]

Thanks. No doubt money and time notwithstanding, the 3L would be the way to go. I like how Griggs packages the whole thing together, and they have a proven record. I have never heard anyone complain about MM's packaging or products either.

Speaking of MM stiffness, does anyone know if the MM k-member brace works with the SVO k-member?

I might throw this hand-grenade over to the corner carvers, but the fact that 4L vs 3L comes down to articulation binding -- and the 3L wins -- would sound completely bonkers to the ultra4 (solid axle) crowd. If I stay with the 4L, it would be out of curiosity of how well their solid axle doctrine of 4L with very serious shock tuning works on the street since I'm updating the Koni's anyway.

And again price. I've found adjustable rear uppers with heim joints for $50 from aliexpress. Boxing in the lowers with spherical joints on the chassis side is less than $100. Dunno, I think the deciding factor is my curiosity, I might just go full rubber stock replacement for now, and then start upgrading slowly so I can get a good feel for the difference it makes, culminating in a full 3L watts link down the road.

Anyone have an opinion on Del-A-Lum bushings? They have a SVO specific kit for the front control arms.

[Art Vandelay]

I have the MM 4 point convertible k-member brace and it fits fine. I used the convertible version because at one point my car had convertible bracing, and I was thinking about keeping it after finishing the subframe connector installation. I'm confident either version will fit the SVO k-member.

My vote goes for MM parts in the rear, because you don't have to upgrade everything at once to get positive results. I also think MM's system is the most tailpipe-friendly of them all if you choose to go all out.

[brsvo]

The Del-a-lum bushing work great for me. I did have to trim them down to get them to fit in the k frame.

[Desert Patina]

Well, one good point, the shocks are really cheap right now at RCA Garage. Just $340 for the front pair. I haven't heard back from Rare Parts yet, nor have I shopped around for a machine shop to rebuilt the front control arms.

Does anyone know where I can source the correct ball joints to rebuilt the front LCA's?

edit:

Looks like anything for the 94-04 Mustangs, Steeda X2 (stull SN95 but for lowered), or the ones used for the Lincoln Mark VII. The latter are reported to need more material removed to make them fit, but have the right taper diameter. The former need a MM adapter, mentioned many times in this forum in the SN95 swaps.

[KevinK]

JTurbo posted over at FEP on the ball joints.

[Laredo]

...Speaking of MM stiffness, does anyone know if the MM k-member brace works with the SVO k-member?....

Yes, I have that brace on my stock SVO K-member.

[Chalky]

Yep, got one on my car, works good. You need to remove to change a starter motor though.

[Desert Patina]

So what priority would you put these...

1) (choose one of the following) a. Torque bar (which supports the rear axle on the front subrails) + Jack rails or b. Subframe connectors
2) (choose one of the following) a. Through the floor subframe connectors or b. bolt on
3) Strut braces (front and rear or either)
4) K-Member brace
5) Torque box re-enforcements
6) Tubular versions of what I already have (front control arms, K-Member, etc...)
7) Spherical joints (wherever you want)
8) Delrin bushings (wherever you want)

I'm going to ask the turbo-ford guys too ...

[Desert Patina]

So it isn't so bad. Let me count it up...

RCAGarage had the cheapest Koni's so I got all four corners (I'm just getting the Gabriels for the quad shocks). Alltogether for the shocks ... about $550. About half what I was budgeting.

I'm only replacing the rear upper control arms (AliExpress), with something with spherical bushings (heim joints) on the frame side and regular rubber (RockAuto) on the axle side. I'm curious how they will hold up. If my bank account recovers I'll likely replace them with Spohn versions before too long.

I'm not touching the rear lowers, because I figure to do that right I'll get a set that doesn't attach to the sway bar, and get an adjustable sway bar instead. I figure all the work to remove binding in the LCA's is worthless with the sway bar attached. That will be a project for a future day. Again, Spohn's are what I'm thinking at this point. But i could just as easily go with the popularly recommended PM3L (panhard + only one UCA).

The front control arms will get some TRW low friction S-95 ball joints pressed in by the local machine shop, and cheap poly bushings both from Amazon.

All the control arms (minus the rear lowers) and bushings comes to about $450.

I'm not changing the springs, I don't think those ever really wear out. It rides high enough, and all four corners are pretty even. But I do have new isolators (cheap poly from RCAGarage).

The only sway bar part I'm doing now is new MOOG end links, from RockAuto.

No subframe connectors or other re-enforcements yet. If I were to do that today, I'd just weld in the torque boxes, and weld in a 2x2 box stock as a through the floor subframe connector.

I think this satisfies my balance of budget, Jackie Stewart deference, and priorities of repairing before really changing anything.

[Desert Patina]

Well, I seem to have found the rosetta stone. The information at the heart of why people hate the Mustang 4-link. A study done by the lead engineer (at one point) of Maximum Motorsports.

While bind is only one of many parameters determining the handling characteristics of a suspension system, it is useful information, and has been a subject of great debate on these message boards. As part of the research we did in developing our rear suspension system, MM has actually done quite a bit of roll-bind testing. I can offer some hard numbers for everyone to consider. I will define ‘bind’ to be any resistance to wheel movement in a roll situation that is not from the spring or sway bar.
Let me say that this information is not intended to be negative toward any particular system, but should be used to gain understanding of the way cars with different setups feel/handle. This information can help everyone to optimize whatever setup they may have.
Of the tests we have done, following are the tests relating to the rear suspension systems most often discussed. All tests are with the sway bar disconnected, cycling one wheel through 3” bump/droop as if in a roll situation. The results are organized in order from least bind to the most bind.
1) 4 Link - LCA with spherical bearings or rod ends at both ends / Stock UCA’s
6lb/in Linear
This shows the stock upper arms introduce 6 lb/in of wheel rate.
2) 4 Link – MM LCA 3 piece poly, spherical bearing / Stock UCAs
9lb/in Linear
This shows an additional 3 lb/in resistance from our 3 piece urethane compared to a rod end.
3) MMTA/PB – LCA with spherical bearings or rod ends at both ends
10lb/in Linear
Here we removes the 6lb/in from the UCAs, but adds 10lb/in due to lateral deflection of the TA during roll (see above post).
4) 4 Link – Stock LCA / Stock UCAs
11lb/in Linear
This shows that the stock LCA adds 5 lb/in of wheel rate, which is actually more than our LCA of case 2.
5) MMTA/PB – MM LCA 3 piece poly, spherical bearing
13lb/in Linear
Again illustrating an additional 3lb/in additional resistance of our 3 piece urethane compared to the rod ends in case 3.
6) 4 Link – LCA with 3 Piece Urethane at both ends / Stock UCAs
26lb/in Linear
Case 6 shows that the 3 piece poly (or any LCA) works best with a spherical bearing at one end. 17lb/in is added over case 2. Note that the effect of adding a 3 piece urethane at only one end adds 3lb/in. Add it at BOTH ends and the increase is 17lb/in… NOT 6 lb/in as one might expect.
7) 4 Link - LCA with delrin, spherical bearing / Stock UCAs
30lb/in Linear
This shows that delrin does not allow necessary angular deflection resulting in an additional 21lb/in over case 2.
8) 4 Link With PB - Stock LCA / Stock UCA
In the first 1” travel 47lb/in
Between 2-3” of travel 30lb/in Decreasing Rate
In case 8 & 9 the Panhard bar defining a new lower roll center is forcing control arms to travel a new path of higher resistance.


9) 4 Link With PB – MM LCA / Stock UCA
In the first 1” travel 50lb/in
Between 2-3” of travel 30lb/in Decreasing Rate
10) 4 Link – Stock LCA / UCA with rod end at chassis, stock rubber at axle
In the first 1” travel 63lb/in
Between 1-2” travel 39lb/in
Between 2-3” travel 20lb/in Decreasing Rate
Case 10 represents trying to locate the axle with a stiffer bushing configuration on the upper control arms. Since the upper arms need to have an effective length change, the rod end in this case actually creates MORE bind.
11) 4 Link – LCA with urethane at both ends / Stock UCA’s
67lb/in Linear
Case 11 is similar to case 6, but shows that a standard poly/poly control arm does not allow much angular change.


Keep in mind that the above information is with no cornering force on the axle. Therefore, there is a huge gap in this information if you are trying to correlate this data to how these systems would feel in use. I would say that the Torque-arm in case 3 & 5 outperforms any other case shown, although it does not have the least amount of bind in this test. We have begun to build a fixture that loads the axle laterally, as if in a corner, to THEN see how the bind behaves. Any system with a Panhard bar should have no significant increase in bind over what is already shown here. This predictability that a PB provides is why we recommend it on a 4 link (with the correct control arms) for people on a budget, or Solo II Street Prepared cars (not allowed to remove uppers). True, you are inducing bind in this situation, but that bind should not significantly change as you load the suspension laterally. When driving the car, the effective added spring rate (from bind) balances well with the new lower RC, and the improved stability and predictability. YES this is a compromise, but I feel it beats trying to locate the axle laterally with stiffer bushings. Obviously, if the pocket book or rulebook permits, the best thing to do is add a Torque-arm and remove the upper control arms. All this binding is also why you are able to add at least 50lb/in wheel rate to the rear when you add a Torque-Arm and remove the UCAs.
Jon- the barrel shaped bushing was designed to maximize contact area and minimize resistance to angular motion. When cycling the suspension in straight bump and droop, its effect is immeasurable.
Ehren VanSchmus
MM Design Engineer

Looks like my $50 investment on Aliexpress would make things worse. I don't quite understand still, but I trust the data. What I don't understand is that I figure the axle would rotate forward rather than change length. I'll have to draw it out to figure it out. Perhaps it has to do with their effective intersection being far behind the axle, meaning if the axle does need to rotate at all both arms will radius around that point and cause a twist in the axle, which will pull one UCA while pushing the other.

Also I talked to a person from MM, and he helped me understand that 4 links may not be that bad, but the Mustang is. The upper control arms are so short that they induce a lot of front to back motion on the top of the axle. And because their effective angle intersection is far behind the axle, it sweeps the axle in bad ways that invoke rear steering. And it is true, the 4link people like the uppers to converge at the top middle of the axle.

So it looks like I'll not touch the rear end, drive it a round for a bit, and then get a panhard bar and go for a PM3L, and then work my way up to a full torque arm.

This and other good information is from this threat at corner carvers... http://www.corner-carvers.com/forums...&threadid=9237

[Desert Patina]

After replacing the rear shocks, it is more than half way better. So now I'm working the front suspension rebuild, the A arms are at the machine shop where he will try the SN95 ball joint replacement.

But I'm really embarrassed, I've owned this thing for 12 years and never noticed it is missing the front sway bar

[Art Vandelay]

Did you talk to MM about the PM3L? I thought they actually recommended keeping all 4 control arms with a panhard bar as an intermediate step. I know a lot of people have seen success with the PM3L but I'd be afraid of tearing the mounts.

[MikeFleming]

But I'm really embarrassed, I've owned this thing for 12 years and never noticed it is missing the front sway bar

So it's like 30 pounds underweight??

[Desert Patina]

I did talk to them about the P3ML, and the sales rep suggested disconnecting one of the uppers with or without a panhard bar (heh, he called it the "pan-hard" bar). And if you can't (because of the rules, etc...) they suggest i consider using pipe insulation as bushing material to effectively negate one. They say they were the ones who invented it.

But to be fair, you are right in the VanSchmus report I quoted, he says directly that even with the problems the 4L + Panhard is the best compromise.

Still, I might break out my dynamics simulation software from college, and try to see the 4L in action.

And yeah, you figure I would have noticed the 30lb difference

On a more serious note, replacing the rear shocks has had two very interesting effects ... 1) Its raised the rear end quite a bit (might be because of the new spring isolators) and 2) it rolls less around the corners. Given I didn't change the springs and still am missing a front sway bar, I wouldn't have expected the rear shocks to have as much of an effect as they did.